- Hydrogen Bonding in Amorphous Alkaline Earth Carbonates
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Amorphous intermediates play a crucial role during the crystallization of alkaline earth carbonates. We synthesized amorphous carbonates of magnesium, calcium, strontium, and barium from methanolic solution. The local environment of water and the strength of hydrogen bonding in these hydrated modifications were probed with Fourier transform IR spectroscopy, 1H NMR spectroscopy, and heteronuclear correlation experiments. Temperature-dependent spin-lattice (T1) relaxation experiments provided information about the water motion in the amorphous materials. The Pearson hardness of the respective divalent metal cation predominantly determines the strength of the internal hydrogen-bonding network. Amorphous magnesium carbonate deviates from the remaining carbonates, as it contains additional hydroxide ions, which act as strong hydrogen-bond acceptors. Amorphous calcium carbonate exhibits the weakest hydrogen bonds of all alkaline earth carbonates. Our study provides a coherent picture of the hydrogen bonding situation in these transient species and thereby contributes to a deeper understanding of the crystallization process of carbonates.
- Leukel, Sebastian,Mondeshki, Mihail,Tremel, Wolfgang
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- Syntheses, structure and properties of Alkaline-earth metal salts of 4-Nitrophenylacetic acid
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The synthesis, crystal structure, spectral characteristics and thermal properties of alkaline-earth metal salts of 4-nitrophenylacetic acid (4-npaH) namely, [Mg(H2O)6](4-npa)2?4H 2O (4-npa = 4-nitrophenyl-acetate) (1), [Ca(H 2O) 2(4-npa) 2] (2) and [Sr(H 2O) 3(4-npa) 2] ?4.5H 2O(3) are reported. In 1, the 4-npa ion functions as a charge balancing counter anion for the octahedral [Mg(H 2O) 6] 2+ unit with the Mg(II) ion situated on a centre of inversion. The two unique lattice water molecules link the [Mg(H 2O) 6] 2+ cations and 4-npa anions with the aid of O-H ?O interactions. Compounds 2 and 3 are one-dimensional (1-D) coordination polymers containing an eight coordinated Ca(II) situated in a general position and a nine coordinated Sr(II) located on a twofold axis. The μ2-bridging tridentate binding modes of the crystallographically independent 4-npa ligands in 2 and the unique 4-npa ligand in 3 link the bivalent metal ions into an infinite chain with alternating Ca ?Ca separations of 3.989 and 4.009 ?, respectively, and a single Sr ?Sr separation of 4.194 ? in the 1-D chain. [Figure not available: see fulltext.]
- Srinivasan, Bikshandarkoil R,Dhavskar, Kiran T,N?ther, Christian
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- Synthesis and characterization of strontium carbonate nanowires with a axis orientation and dendritic nanocrystals
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Strontium carbonate nanowires that grow along the a axis were synthesized in large scale through simple hydrothermal approach for the first time. The aspect ratio of the product is more than 1000. Dendritic nanocrystals were also generated at low temperatures. Moreover, this method is feasible to be applied in the synthesis of barium carbonate nanowires.
- Huang, Qing,Gao, Lian,Cai, Ye,Aldinger, Fritz
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- Direct synthesis of Sr3Al2(OH)12 from solution for preparation of fine-grained Sr3Al2O6 phosphors at low temperature
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The precursors Sr3Al2(OH)12 can be directly precipitated from solution near room temperature under the normal pressure. The cubic Sr3Al2O6 with fine grain size can be synthesized from Sr3Al2(OH)12 at the temperature as low as 600 °C. Especially, the rare earth element, such as Eu3+ etc., as luminescent center, has been simultaneously integrated into the lattices of Sr3Al2O6. The luminescent intensities of the samples annealed at a temperature over 800 °C are strong enough for phosphors, and increase with the annealing temperatures, reach a maximum at 1200 °C and then drop down at 1300 °C. The grain sizes of all the samples annealed below 1200 °C are smaller than 1 μm and suitable for mixing with other phosphors in the applications. The photoluminescent spectra of the Sr3Al2O6:Eu3+ reveal that the intensities of both emission and excitation peaks increase with the dose of Eu3+, and reach maxima at the dose level about 1.2%, then decrease due to concentration quenching. A new excitation band at 230 nm has been observed in heavier doped samples due to the complex point defects produced by association.
- Qi, Jianquan,Zhang, Xinyi,Han, Xiumei,Li, Yuanyuan,Wu, Xueyang,Zhong, Ruixia,Guo, Rui
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- Electrical characterization of strontium tartrate single crystals
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The a.c. and d.c. conductivity of SrC4H4O 6·3H2O are measured and are found to lie between usual conductivities of semiconductor and insulator. Temperature dependence of d.c. conductivity shows intrinsic conduction, which is confirmed by the slope of lnσ versus lnf data. Due to application of thermal energy, noticeable conductivity peaks imply liberation of water molecules during dehydration and the formation of strontium oxalate. The conductivity plot has a nature similar to the intrinsic-to-extrinsic transition found in normal semiconductors. There occurs Efros hopping conduction in our samples.
- Arora,Patel, Vipul,Patel,Amin, Brijesh,Kothari, Anjana
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- Localization of Co2- anion radicals in strontium carbonate obtained by thermal decomposition of strontium oxalate
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Mn2+ EPR probes and transmission electron microscopy are used to study the influence of the thermal decomposition rate of strontium oxalate monohydrate on the morphology and the extended defects in the SrCO3 formed. The correlations
- Stoyanova, R.,Angelov, S.,Bozhilov, K.
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- Single-step synthesis of SrMoO4 particles from SrSO4 and their anti-corrosive activity
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The transformation of three different sizes (4 mineral powder into SrMoO4 scheelite-type tetragonal particles was investigated via conventional hydrothermal treatments under both static and stirring conditions (20 rpm) at 100-250 °C and varying reaction intervals (0.08-48 h) in alkaline solutions saturated with MoO42-. A partial SrSO4 transformation was found to proceed in mild to concentrated alkaline NaOH solutions (0.1-2.5 M), the complete transformation of SrSO4 to SrMoO4 was observed to proceed at temperatures lower than 200 °C over 48 h in a static 5 M NaOH solution, but this process was accelerated when the autoclave was stirred at 20 rpm during the treatment, which led to the production of uncontaminated SrMoO4 particles at 200 °C within 6 h. The resultant SrMoO4 particles had octahedral bipyramidal morphology and particle sizes between 1 and 5 μm; these particles exhibited a noticeable agglomeration at the intermediate and final stages of the reaction due to the formation of agglomerates with an average size of 60 μm. However, stirring of the mixture in the autoclave markedly reduced the growth of the bulky agglomerations of SrMoO4 particles. A coupled process involving the bulk dissolution of the SrSO4 powder and, subsequently, the massive precipitation of SrMoO4 in an alkaline solution (5 M NaOH) saturated with MoO42- ions was utilised to crystallise the SrMoO4 particles. Kinetic studies demonstrated that the activation energy required for the formation of the octahedral shaped SrMoO4 particles was 25.8 kJ mol-1 in the system without agitation; in contrast, the activation energy decreased to 12.8 kJ mol-1 when the transformation was stirred. In a subsequent investigation, the ionic permeability resistance of a commercial paint applied to a AISI 1020 steel substrate was improved by adding a 2.0 wt.% of the transformed SrMoO4 particles to the paint.
- Diaz-Algara,Rendón-Angeles,Matamoros-Veloza,Yanagisawa,Rodriguez-Galicia,Rivera-Cobo
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- Ca(II), Sr(II) and Ba(II) ion interaction with the rheumatoid arthritis drug tenoxicam: Structural, thermal, and biological characterization
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Recently, one of the most common conditions that manifests as joint and muscle inflammation is rheumatoid arthritis. One of the treatments for this arthritis includes non-steroidal anti-inflammatory drugs (NSAIDs) of the oxicam family, and the widest used drug in this family is tenoxicam (Tenox). In this study, the complexation properties of the drug Tenox with Ca(II), Sr(II) and Ba(II) ions in a (dichloromethane + water) binary solvent system are reported. The formed metal complexes were characterized structurally, thermally, and biologically. Tenox was found to act as a chelate monoanionic ligand towards all metal ions with complexation stoichiometry of 1:2 (Metal: Tenox) for Ca(II) and Sr(II) ions, and 1:1 for Ba(II) ions. The Tenox ligand behaves as a bidentate ligand when coordinated with Sr(II) or Ba(II) ions and as a tridentate ligand when coordinated with Ca(II) ions. The Sr(II) and Ba(II) complex of the Tenox ligand exhibited marked inhibitory effect on the cell growth of the C. albicans species.
- Adam, Abdel Majid A.
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- Solvothermal synthesis of fusiform hexagonal prism SrCO3 microrods via ethylene glycol solution
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Fusiform hexagonal prism SrCO3 microrods were prepared by a simple solvothermal route at 120 °C, and characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy. By controlling the content of ethylene glycol (EG), it was found that ethylene glycol (EG) played an important role in the formation of such SrCO3 microrods. Finally, effects of other solvents on the products, including 1,2-propanediol and glycerin, were also investigated.
- Shi, Liange,Du, Fanglin
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- Room temperature syntheses and thermal behaviors of hydrogarnets Sr3M2(OH)12 (M = Al, Cr and Fe)
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Hydrogarnets Sr3M2(OH)12 (M = Al, Cr and Fe) were synthesized through a solid state reaction at room temperature with Al(NO3)3·9H2O, CrCl3·6H2O, FeCl3·6H2O, Sr(NO3)2 and NaOH as the starting materials. All X-ray diffraction (XRD) data of Sr3M2(OH)12 were indexed by the cubic system with the space group of Ia-3d. XRD, differential thermal analysis and thermogravimetric (DTA-TG), and scanning electron microscopy (SEM) were employed to investigate the structural stability, thermal properties and morphologies of Sr based hydrogarnets. The cause of room temperature synthesis and the thermal decomposition behaviors of Sr-based hydrogarnets Sr3M2(OH)12 (M = Al, Cr and Fe) are discussed.
- Chen, Yun-Feng,Yang, Zhi,Li, Yong-Ming,Guo, Jing,Fu, Wen-Fu,Wang, Ying-Xia,Liao, Fu-Hui,Li, Jianye
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- Heat capacity and thermal expansion coefficient of SrCeO3(s) and Sr2CeO4(s)
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SrCeO3(s) and Sr2CeO4(s) were synthesized by citrate-nitrate gel combustion and solid state methods, respectively. Heat capacity of SrCeO3(s) and Sr2CeO4(s) were measured in high pure oxygen atmosphere by differential scanning calorimetry in the temperature range of 300-870 K. Enthalpy, entropy and Gibbs energy functions were computed from the heat capacity data for SrCeO3 and Sr 2CeO4(s) in the temperature range of 298-870 K and 298-600 K respectively. Thermal expansion measurements of these compounds were carried out in the temperature range of 298-1273 K by high temperature X-ray powder diffractometry. The average value of coefficient of volume expansion for SrCeO3 and Sr2CeO4(s) were calculated in the temperature range of 298-1273 K to be (10.79 ± 2.31) and (23.22 ± 5.19) × 10-6 K-1, respectively.
- Sahu, Manjulata,Krishnan,Nagar,Saxena,Dash, Smruti
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- One-pot synthesis and microwave absorbing properties of ultrathin SrFe12O19 nanosheets
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Ultrathin SrFe12O19 nanosheets were successfully synthesized by modified hydrothermal method. The structure, morphology and properties were characterized and investigated by using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Vibrating sample magnetometer (VSM) and Vector network analyzer (VNA). The results revealed that the temperature and diethylene glycol were responsible for ultrathin structure and good dispersity of SrFe12O19 nanosheets. The SrM nanosheets showed strong magnetocrystaline anisotropy and large coercive force, which enhanced microwave absorbing properties of SrFe12O19. The reflection loss (RL) of a composite absorber with thickness of 3.5 mm reached a maximum value of ?28.6 dB and the effective absorption bandwidth (RL ?10 dB) was 0.92 GHz at the high frequency region, exhibiting excellent microwave absorbing properties as promising microwave absorber.
- Dong, Shenhui,Lin, Chucheng,Meng, Xianfeng
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- Mechanical and thermal carbonation of strontium ferrite SrFeOx
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Reaction of non-stoichiometric SrFeOx (2.5 ≤ x ≤ 3.0) with carbon dioxide induced by high temperature and mechanical energy was investigated. The high-temperature reaction route was found to convert SrFeOx to a mixture of SrFe12O19 and SrCO3 at temperatures below 1128 K under 0.98 atm of CO2 pressure. The mechanical reaction carried out at room temperature causes a complete decomposition of SrFeOx to strontium carbonate and hematite via a metastable ferric carbonate phase. We examined the phase transformations, the reaction kinetics and morphology of carbonated SrFeOx and compared the two processes.
- Schmidt
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- Photoluminescence of the SrS:Mn2+ phosphor and Pb 2+-sensitized luminescence of the SrS:Pb2+, Mn 2+ phosphor
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Emission and excitation spectra of the Mn2+ ion in the SrS:Mn2+ and SrS:Pb2+ ,Mn2+ phosphor are investigated at various temperatures. The analysis of the excitation spectra of the Mn2+ emission band leads to the Racah parameters 5=712 cm -1, C= 3352 cm-1 and the crystal field parameter Dq=516 cm-1 with the covalency parameter ε=0.046. By the transient spectroscopy technique, it is found that the emision band due to the single Mn2+ ion center has a peak at 553 nm and a decay time of ~5.5 ms, while that due to the paired Mn2+ center has a peak at 565 nm and a decay time of 0.6 ms. Energy transfer from Pb2+ ion to Mn 2+ ion is observed in SrS:Pb2+,Mn2+. By observing the change of band shapes, the intensities and decay characteristics of both the Pb2+ and Mn2+ luminescence, it is concluded that the transfer is of resonance type. It is found that the energy of Pb 2+ ion is transferred preferentially to the isolated Mn2+ ion.
- Matsuyama, Isamu,Yamashita, Nobuhiko,Nakamura, Kaizo
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- Electrochemical study of cathodic electroprecipitation of strontium hydroxide films from dimethyl sulfoxide-based solvents
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Films of strontium hydroxide and related compounds have been galvanostatically electrodeposited on silver tapes in organic Sr(II) nitrate and chloride solutions using dimethyl sulfoxide (DMSO) because of its high dissolving power and some water as the hydroxide ion precursor. The influence of the nature of the solvent, electrolyte concentrations, and current applied during deposition on film microstructure and composition have been investigated by means of voltammetry, chronoamperometry, and ex situ spectroscopic methods: X-ray diffraction, scanning electron microscopy, electron microprobe analysis, and inductively coupled plasma spectrophotometry. Films were found to be crystalline after formation at ambient temperature whatever the conditions. Optimal current ranges were determined for each electrolyte/solvent couple in terms of adherence and homogeneity of the precursor. The electroprecipitation mechanism has been completed in pure DMSO by a subsequent chemical reaction between strontium hydroxide and atmospheric CO2 giving rise to crystallized strontium carbonate. In acetonitrile + DMSO mixtures, the chloride phase SrCl2 · 2H2O has also been identified as coprecipitated with Sr(OH)2 because of the low solubility of the electrolyte in pure acetonitrile.
- Lepiller,Poissonnet,Legendre,Giunchi
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- Comparative study regarding the formation of La1-xSr xCrO3 perovskite using unconventional synthesis methods
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The synthesis of strontium-doped lanthanum chromite, La 1-xSrxCrO3 (x=0.1 and 0.3), used as an interconnect material for solid oxide fuel cells (SOFC), was investigated using two unconventional synthesis methods: (1) organic precursors' method based on the thermal conversion of complex combination resulted in the oxidation reaction of 1,2-ethanediol by La3+, Sr2+ and Cr3+ nitrates; (2) combustion synthesis based on the exothermic redox reaction of La3+, Sr2+ and Cr3+ nitrates with urea and glycine as fuels. We also used a mixture of urea and glycine as fuel. The samples were characterized by means of thermal analysis and X-ray diffraction.
- Iano?,P?curariu,Laz?u,Iano?ev,Ecsedi,Lazǎu,Barvinschi
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- Preparation, crystal structure, thermal decomposition mechanism and thermodynamical properties of [Yb(NTO)3(H2O)4]·6H2O and [Sr(NTO)2(H2O)4]·2H2O
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[Yb(NTO)3(H2O)4]·6H2O was prepared by mixing the aqueous solution of lithium 3-nitro-1, 2, 4-triazol-5-onate and the dilute nitric acid solution of ytterbium oxide. The single crystal structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, space group C2/c with crystal parameters of a = 3.6931 (5)nm, b = 0.6683(10) nm, c = 2.5656(3) nm, β = 130.974(5)°, V = 4.7811(11) nm3, Z = 8, μ = 40.17 cm-1, F(000) = 2850, Dc = 2.013 g cm-2, and λ(MoKα) = 0.071073 nm. The final R is 0.0258. [Sr(NTO)2(H2O)4]·2H2O was prepared by mixing the aqueous solution of 3-nitro-1, 2, 4-triazol-5-one and the excessive strontium carbonate. The single crystal structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, space group P21/c with crystal parameters of a = 1.1034(1) nm; b = 2.2742(2) nm, c = 0.63398(9) nm, β = 101.798(13)°, V = 1.5573(4) nm3, Z = 4, Dc = 1.936 g cm-3, μ = 35.45 cm-1, F(000) = 912, λ(MoKα) = 0.071073 nm. The final R is 0.0347. Based on the results of thermal analysis, the thermal decomposition mechanism of [Yb(NTO)3(H2O)4]·6H2O and [Sr(NTO)2(H2O)4]·2H2O were derived. From measurements of the enthalpy of solution of [Yb(NTO)3(H2O)4]·6H2O and [Sr(NTO)2(H2O)4]·2H2O in water at 298.15 K, the standard enthalpy of formation, lattice energy, lattice enthalpy and standard enthalpy of dehydration have been determined as -(3853.3 ± 6.8) and -(2545.2 ± 4.7), -4596 and -2114, -4631 and -2136, 391 and 67.2 kJ mol-1, respectively.
- Jirong, Song,Rongzu, Hu,Bing, Kang,Fuping, Li
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- Growth of La1-xSrxFeO3 thin films by atomic layer deposition
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Thin films of La1-xSrxFeO3 have been prepared by the ALD (atomic layer deposition) technique using La(thd) 3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Sr(thd)2, Fe(thd)3, and ozone as
- Lie, Martin,Nilsen, Ola,Fjellvag, Helmer,Kjekshus, Arne
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- Oxygen permeability and ionic conductivity of perovskite-related La0.3Sr0.7Fe(Ga)O3-δ
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The oxygen ionic conductivity of La0.3Sr0.7Fe1-xGax O3-δ (x = 0.2-0.4), determined by oxygen permeation, faradaic efficiency, and total conductivity measurements at 1023-1223 K, is essentially independent of oxygen chemical potential and structural changes in the wide oxygen partial pressure range from 10-14 to 0.21 kPa. At oxygen pressures close to atmospheric air, the ion transference numbers of perovskite-like La0.3Sr0.7Fe(Ga)O3-δ phases vary from 4 × 10-4 to 4 × 10-2, increasing with gallium content and temperature. Although there is a great difference between ionic and p-type electronic conductivities in oxidizing atmospheres, the electron-hole conduction was demonstrated to affect oxygen permeation and ambipolar conductivity. In oxidizing conditions, the oxygen permeability of La0.3Sr0.7Fe1-xGax O3-δ (x = 0-0.4) membranes increase with increasing x. The bulk ionic transport process and surface exchange kinetics both influence the permeation through La0.3Sr0.7FeO3-δ ceramics, whereas the oxygen fluxes through Ga-containing materials are predominantly determined by the bulk ambipolar conduction. Thermal expansion coefficients of La0.3Sr0.7Fe1-xGaxO 3-δ (x = 0-0.4) in air vary in the range (11.7-14.9) × 106 K-1 at 300-800 K and increase up to (19.5-26.4) × 106 K-1 at 800-1170 K. Substitution of iron with gallium was found to suppress both thermal expansion and chemically induced expansion of La0.3Sr0.7Fe(Ga)O3-δ materials, originating from oxygen nonstoichiometry variations under changing the oxygen partial pressure.
- Kharton,Yaremchenko,Viskup,Patrakeev,Leonidov,Kozhevnikov,Figueiredo,Shaulo,Naumovich,Marques
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- Electrodeposition of oriented SrCO3 coatings on stainless steel substrates
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Cathodic reduction of a strontium bicarbonate bath stabilized by a variety of amine-carboxylic acids as ligands resulted in the deposition of micrometers-thick SrC O3 coatings by electrogeneration of base. The use of diethylenetriaminepentaacetic acid (DTPA) yielded SrC O3 coatings with a distinct c -axis orientation. The degree of orientation is higher in thick rather than thin coatings. The degree of orientation is also reduced when the DTPA concentration is increased or the pH is increased. These observations suggest that oriented crystal growth is due neither to the template effect of the substrate nor any additive mediated interaction due to DTPA but is solely due to the kinetics of crystallization. The Sr[DTPA] complex has the highest stability constant among the ligands studied, indicating the low degree of supersaturation in this bath compared to those stabilized by other complexing agents. SrC O3 deposition is a good model for the study of aragonite CaC O3 deposition by virtue of being isostructural with the latter and having the smallest lattice mismatch with aragonite among the heavier metal carbonates.
- Joseph, Sumy,Kamath, P. Vishnu
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- Facile conversion of layered ruddlesden-popper-related structure y 2O3-doped Sr2CeO4 into fast oxide ion-conducting fluorite-type y2O3-doped CeO2
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The present work shows a new solid- and gas-phase reaction technique for the preparation of a fast oxide-ion-conducting Y2O3-doped Ce1-x-YxO2-δ (x = 0.1, 0.2) (YCO), which involves the reaction of lay
- Gerlach, Ryan Georg,Bhella, Surinderjit Singh,Thangadurai, Venkataraman
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- Thermal investigation of strontium acetate hemihydrate in nitrogen gas
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The thermal decomposition of strontium acetate hemihydrate has been studied by TG-DTA/DSC and TG coupled with Fourier transform infrared spectroscopy (FTIR) under non-isothermal conditions in nitrogen gas from ambient temperature to 600°C. The TG-DTA/DSC experiments indicate the decomposition goes mainly through two steps: the dehydration and the subsequent decomposition of anhydrous strontium acetate into strontium carbonate. TG-FTIR analysis of the evolved products from the non-oxidative thermal degradation indicates mainly the release of water, acetone and carbon dioxide. The model-free isoconversional methods are employed to calculate the E a of both steps at different conversion α from 0.1 to 0.9 with increment of 0.05. The relative constant apparent E a values during dehydration (0.5α0.9) of strontium acetate hemihydrate and decomposition of anhydrous strontium acetate (0.5α0.9) suggest that the simplex reactions involved in the corresponding thermal events. The most probable kinetic models during dehydration and decomposition have been estimated by means of the master plots method.
- Duan,Li,Yang,Cao,Hu,Wang,Liu,Wang
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- Transport properties of LaSrNi1-xScxOy solid solutions
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The formation of LaSrNiO4- and LaSrScO4-based solid solutions with the general stoichiometry LaSrNi1-xSc xO4 (0 x 1) has been studied in air at temperatures from 700 to 1300°C. According to x-ray
- Savchenko,Makhnach,Emel'yanova,Pan'kov
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- Preparation and characterization of monodispersed YSZ nanocrystals
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A novel method for large-scale preparation of yttria-stabilized zirconia (YSZ) nanocrystals is presented. The hydrous YSZ colloidal nanoparticles are self-assembled on the surface of SrCO3 nanoparticles by a sonochemical method. After calcination, fully crystalline monodispersed YSZ nanoparticles are obtained, and the SrCO3 is washed out by 10% HNO3 solution. The agglomeration of YSZ particles is inhibited as the crystallization occurs on the surface and interface of SrCO3 nanoparticles. The nanocrystals are monodispersed with an average particle size of 4.7 nm and a high surface area of 165 m2/g. The quantum confinement effect is observed: the band gap increases from 4.13 eV for the agglomerated sample to 5.44 eV for the monodispersed YSZ nanocrystals.
- Pang, Guangsheng,Chen, Siguang,Zhu, Yingchun,Palchik, Oleg,Koltypin, Yuri,Zaban, Afie,Gedanken, Aharon
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- Thermal decomposition study [MCu(C3H2O4)2(H2O) n] phases (M is Ca (n = 3), Sr and Ba (n = 4))
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Three new compounds with the general formula [MCu(C3H2O4)2(H2O) n] (M is Ca (n = 3), Sr and Ba (n = 4)) have been synthesized and characterized by analytical and infrared techniques. X-ray
- Insausti,Gil De Muro,Lorente,Rojo,Bocanegra,Arriortua
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- Preparation and formation mechanism of three-dimensionally ordered macroporous (3DOM) MgO, MgSO4, CaCO3, and SrCO 3, and photonic stop band properties of 3DOM CaCO3
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Three-dimensionally ordered macroporous (3DOM) magnesium (Mg) oxide (MgO), MgSO4, calcium (Ca) carbonate (CaCO3), and strontium (Sr) carbonate (SrCO3) were prepared using a colloidal crystal of polymer spheres as a template. Ethanol or ethanol-water solution of metal salts (acetate or nitrate) and citric acid was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating of this PMMA-metal salt-citric acid composite produced the desired well-ordered 3DOM materials with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible (UV-vis) diffuse reflectance spectra. The presence of citric acid is crucial for production of the 3DOM structures. Reaction of citric acid with metal salt produces metal citrate solid in the void of PMMA spheres, which is necessary to maintain the 3DOM structure during the calcination process. 3DOM CaCO3 shows opalescent colors because of it's photonic stop band properties.
- Sadakane, Masahiro,Kato, Rika,Murayama, Toru,Ueda, Wataru
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- Effects of nanostructure on catalytic degradation of ethanol on SrCO 3 catalysts
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Degradation of ethanol over SrCO3 nanowires and nanoparticles was used as a model reaction to investigate the effect of nanostructure on chemical property. Differences in catalytic degradation activity with nanostructure are evaluated. The results indicated that catalytic activity of SrCO3 particles increases with decreasing of particle size due to high surface area. But this conclusion cannot be applicable to evaluating SrCO3 nanowires and nanoparticles. SrCO3 nanowires have lower ignition temperatures and wider working temperature ranges than SrCO 3 nanoparticles, though nanowires had lower surface areas. Besides, ethanol degraded over nanowires in three ways, and the dominating reaction changes with reaction temperature. Consequently, the main degradation products of nanowires differed with temperature. But for nanoparticles, acetaldehyde is the only main product. Since transmission electron microscopy, X-ray diffraction, and bond equilibrium theory analysis demonstrated that nanowires and nanoparticles had similar crystal structure, surface area, and grain size, the differences in catalytic degradation activity between SrCO3 nanowires and nanoparticles can be attributed to different distributions of active sites, as proven by CO2 and ethanol temperature programmed desorption. ? 2005 American Chemical Society.
- Wang, Li,Zhu, Yongfa
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- Strontium ferrite nanoparticles synthesized in presence of polyvinylalcohol: Phase composition, microstructural and magnetic properties
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Systematic study was devoted to the synthesis of hexagonal strontium ferrite nanoparticles employing polyvinylalcohol as stabilizing agent. Preliminary experiments allowed to select an optimal sol having molar ratio Sr2 + / Fe3 + = 12, weight ratio PVA / [Sr2 + + Fe3 +] = 1.4 and pH = 2.1. The obtained sol were transformed to gels by an evaporation of water at 100 °C and drying at 112 °C under vacuum. The subsequent calcination was carried out for 3 h at 400 °C, achieved by heating rate of 17 K/min. The obtained precursor was used for a detail study of influence of annealing conditions (temperature range 600-700 °C, annealing time 10-190 min) on the resulting properties. Semiquantitative X-ray phase analysis approved a gradual increase of the M-phase content and a gradual growth of M-phase crystallites with temperature and time. Magnetic measurements showed a distinct influence of the phase composition, namely ratio of the contents of M-phase and maghemite on the shape of the magnetic loops, while the crystallite sizes have only a slight effect.
- Veverka,Kní?ek,Pollert,Bohá?ek,Vasseur,Duguet,Portier
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- Dry mechanochemical conversion of SrSO4 to SrCO3
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The effect of milling time on the dry conversion of celestite, SrSO4, to SrCO3 using sodium carbonate in a planetary type ball mill was investigated. After milling, the powders were leached in distilled water at room temperature and the solids then washed with 1 N HCl to separate the products. X-Ray diffraction analysis showed that SrSO4 started to transform to SrCO3 within 10 min of milling and the extent of conversion increased with milling time reaching >90% after 30 min. A 3 was obtained in 30 min by increasing the molar ratio of Na2CO3:SrSO4 to 1.3:1.
- Setoudeh,Welham,Azami
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- Thermal expansion, microhardness and oxygen permeation of La1-xSrxCo0.8Fe0.2O3+δ membranes
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Dense ceramic membranes acting as oxygen and electron ion-conductors can be used as the catalysts for syngas production. The La1-xSrxCo0.8Fe0.2O3+δ (LSCF) systems were known to have a high ionic and electronic conductivity. In the application, the La1-xSrxCo0.8Fe0.2O3+δ membranes required low thermal expansion, microhardness and high oxygen permeation flux. The changes in the expansion, hardness, and oxygen flux of the La1-xSrxCo0.8Fe0.2O3+δ perovskite membranes with various strontium substitutions were studied. The magnitude of both the thermal expansion and the oxygen content of the La1-xSrxCo0.8Fe0.2O3+δ membranes decreased with up to 20 % strontium substitution and then increased with 30 and 40 % strontium ion substitution. Meanwhile, the hardness and shrinkage improved by various strontium ion substitutions, except with 20 % strontium. The highest oxygen flux over La1-xSrxCo0.8Fe0.2O3+δ (0.0 ≤ x ≤ 0.4) membranes in the surface exchange-controlled processes was found of the membrane with 30 % strontium substitution.
- Aliyatulmuna,Utomo,Burhan,Fansuri,Murwani
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- An easy method to prepare nanowire
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SrCO3 nanowires and BaCO3 nanowires with single crystal structure and aspect ratio of about 1000 were prepared by a simple reaction without template. Preferentially assembling-reconstruction of colloidal particles was supposed as the formation mechanism.
- Wang, Li,Zhu, Yongfa
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- Nanophase formation of strontium hexaferrite fine powder by the sonochemical method using Fe(CO)5
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A fine strontium hexaferrite powder has been successfully synthesized by a sonochemical method employing Fe(CO)5 and SrCO3. SrCO 3 was first synthesized using strontium nitrate and urea, and it was found that applying ultrasound radiation during this process results in the uniform formation of SrCO3 hexagonal rods. These rods were then dispersed with in situ generated amorphous Fe2O3, using Fe(CO)5 as the source. The resultant precursor was then calcined at 900°C, which is lower than the conventional solid-state reaction of applying 1300°C to get the strontium hexaferrite fine powder. This sonochemically derived ferrite exhibited an intrinsic coercivity of ~4600 Oe and a saturation magnetization of ~60 emu/g at 20 K and ~32 emu/g at 300 K.
- Sivakumar,Gedanken,Zhong,Du,Bhattacharya,Yeshurun,Felner
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- Hydrogen separation using proton-conducting perovskites
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Two methods of hydrogen separation using proton-conducting perovskites, electrochemical hydrogen pumping with proton-conducting electrolytes and hydrogen sieving through protonic-electronic mixed conductors, are stated. In the former case, high temperature proton conductors (HTPCs) enable the hydrogen transport by external application of electricity. In the latter case, it is a fundamental concern how the protonic and electronic charge carriers coexist in oxides to allow hydrogen permeation. Experimental results and the problems for future investigations are discussed.
- Matsumoto, Hiroshige,Shimura, Tetsuo,Iwahara, Hiroyasu,Higuchi, Tohru,Yashiro, Keiji,Kaimai, Atsushi,Kawada, Tatsuya,Mizusaki, Junichiro
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- Shape evolution of SrCO3 particles in the presence of poly-(styrene-alt-maleic acid)
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In this paper, strontium carbonate particles with different morphologies were prepared by a simple precipitation reaction of sodium carbonate with strontium nitrate in the absence and presence of poly-(styrene-alt-maleic acid) (PSMA). The as-prepared products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the concentration of PSMA on the morphologies and phase structures of strontium carbonate particles were investigated and discussed. The results showed that SrCO 3 particles with various shapes, such as bundles, dumbbells, irregular aggregates and spheres could be obtained by varying the concentration of PSMA. A schematic illustration was proposed to account for the shape evolution of the as-prepared SrCO3 particles.
- Yu, Jiaguo,Guo, Hua,Cheng, Bei
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- Hydrogen permeation and chemical stability of In-doped SrCe 0.95Tm0.05O3-δ membranes
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A series of SrCe0.95-xIn xTm0.05O3-δ (x = 0.00, 0.05, 0.10, 0.15, 0.20) samples were prepared by the sol-gel technique using ethylenediaminetetraacetic acid and citric acid as the complexing agents. The X-ray diffraction (XRD) measurements were carried out to study the formation of SrCe0.75In0.20Tm0.05O3 -δ oxide. The results indicate that In can dissolve in the orthorhombic lattice of strontium cerate to form a solid solution at 1300 °C. The effects of In doping on the sinterability, chemical stability and hydrogen permeation flux of SrCe0.95Tm0.05O 3-δ oxides were investigated by a variety of characterization methods. According to the results of XRD and scanning electron microscopy (SEM), increasing In content in the oxides causes lattice constriction and promotes grain growth during sintering process at 1300°C. The relative density and morphology variation of the sintered membranes reveals that In doping improves the sintering activity of SrCe0.95Tm 0.05O3-δ membrane. The stability test shows that the stability of strontium cerate against CO 2 increases with the increasing In content. Hydrogen permeation through the SrCe0.95-xInxTm 0.05O3-δ membranes was carried out between 700 and 900°C using 40% H2/He mixture as feed gas and Ar as sweep gas, respectively. The H2 permeation flux decreases with the increase of the In content. Activation energies of SrCe 0.95Tm0.05O3-δ, SrCe0.85In0.10Tm0.05O3 -δ and SrCe0.75In0.20Tm 0.05O3-δ are 36.61, 52.25 and 73.06 kJ/mol, respectively.
- Yuan, Wenhui,Xiao, Chichi,Li, Li
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- Reactions within the system, 2SrCO3-Fe2O3: Part I. CO2 atmosphere
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Simultaneous TG/DSC and high temperature X-ray diffraction studies were performed on the system SrCO3-Fe2O3 in an atmosphere of CO2 from room temperature to 1300°C. SrCO 3 decomposes and reacts simultaneously with the Fe2O 3 beginning around 850°C. A transient iron rich phase is formed initially, which soon diminishes to yield a mixture of perovskite SrFeO 3-x and the iron rich phase Sr4Fe6O 13. Upon cooling the perovskite phase predominantly orders into the brownmillerite structure Sr2Fe2O5. There does not appear to be a Hedvall effect associated with the first order phase transformation in SrCO3 at 927°C.
- Gallagher,Sanders,Woodward,Lokuhewa
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- Qualitative study on the reaction of Bi1.8Pb0.4Ca2Sr2Cu3Oy superconductor with water
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When Bi1.8Pb0.4Ca2Sr2Cu3Oy powders were immersed into deionized water, a large quantity of Ca2+ and Sr2+ ions was detected in the aqueous solution, indicating the decomposition of the Bi1.8Pb0.4Ca2Sr2Cu3Oy superconductors in water. The pH of the solution was initially increased rapidly to 11.1 due to the formation of OH- ions. However, after 30 min, in the open system, the Ca2+ and Sr2+ ions would further react with CO2 in the atmosphere to form sparingly soluble carbonates and the pH of the solution was slowly decreased to 9.81 over 20 h. Only a small amount of Bi3+, Pb2+ and Cu2+ ions was detected in the aqueous solution. Non-soluble products, such as Bi2CuO4, CuO and Cu6PbO8, were observed in the reaction residue which might act as a barrier to prevent deterioration of the superconductor with water in the bulk sample. The chemical equation was given as Bi1.8PbxCa2Sr2Cu3Oy(s) + 4H2O → 2Ca(aq)2+ + 2Sr(aq)2+ + 8OH(aq)- + 0.9Bi2CuO4(s) + xCu6PbO8(s) + (3-0.9-6x)CuO(s).
- Wei,Wang,Kao
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- Two three-dimensional metal-organic frameworks constructed from alkaline earth metal cations (Sr and Ba) and 5-nitroisophthalicacid - Synthesis, charaterization, and thermochemistry
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Two MOFs of [SrII(5-NO2-BDC)(H2O) 6] (1) and [BaII(5-NO2-BDC)(H 2O)6] (2) have been synthesized in water using alkaline earth metal salts and the rigid organic ligand
- Chen, Sanping,Shuai, Qi,Gao, Shengli
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- Influence Ca-doped SrIn2O4 powders on photoluminescence property prepared one step by ultrasonic spray pyrolysis
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Crystalline Ca-doped SrIn2O4 structures were prepared by a rapid and efficient Ultrasonic Pyrolysis Spray (USP) method. The Sr1-xCaxIn2O4 (x = 0, 0.1, 0.2, 0.3, 0.4 and 1 mol %) samples wer
- Medeiros,Santiago,Ferreira,Li,Longo,Bomio,Motta
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- A novel spray-pyrolysis technique to produce nanocrystalline lanthanum strontium manganite powder
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Nanocrystalline, single phase, and highly homogeneous La 0.84Sr0.16MnO3 (LSM) powder was prepared by a unique spray-pyrolysis process for solid oxide fuel cell applications. Atomization of a citrate-nitrate precursor solution consisting of La 3+, Sr2+, and Mn2+ ions in the molar ratio 0.84:0.16:1.0, which can initiate a controlled exothermic anionic oxidation-reduction reaction leading to a self-propagating auto-ignition (self-ignition) reaction within individual droplets led to the conversion of the precursor to their corresponding single-phase LSM powder. Characterization of the as-sprayed and calcined products by X-ray powder diffraction, thermal analysis, and microstructural analysis confirmed the formation of nanocrystalline single-phase LSM powder by this process.
- Kumar, Abhoy,Devi, Parukuttyamma Sujatha,Das Sharma, Abhijit,Maiti, Himadri Sekhar
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- Freeze dried strontium and iron acetate as reactive precursor for the iron-strontium-oxide complex
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The thermal decomposition of reactive freeze-dried acetate precursors for Sr-Fe-oxides was investigated by means of DTA, TG, mass spectroscopy and X-ray powder diffractometry. In the case of decomposition of Fe(III)-μ-oxo-acetate four superimposed main steps are characterized as release of (a) H2O, (b) acetic acid and ketene (c) methane, ketene and CO2 and (d) acetone and CO2. On careful decomposition, single phase γ-Fe2O3 can be formed. The decomposition of freeze-dried mixed Fe-Sr-acetates reflects some aspects of the single acetates, but also an interaction between the components. The interactions result in a lower decomposition temperature of Sr-acetate (release of acetone and formation of SrCO3). The decomposition temperature of SrCO3 in the reactive mixture is also lowered. The simultaneous decomposition of SrCO3 and its reaction with the Fe-component results directly in the formation of the expected complex Sr-Fe-oxide.
- Langbein,Roesler,Boerger
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- Tetrahedrally Coordinated sp3-Hybridized Carbon in Sr2CO4Orthocarbonate at Ambient Conditions
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We have synthesized the orthocarbonate Sr2CO4, in which carbon is tetrahedrally coordinated by four oxygen atoms, at moderately high pressures [20(1) GPa] and high temperatures (≈3500 K) in a diamond anvil cell by reacting a SrCO3 single crystal with SrO powder. We show by synchrotron powder X-ray diffraction, Raman spectroscopy, and density functional thoery calculations that this phase, and hence sp3-hybridized carbon in a CO44- group, can be recovered at ambient conditions. The C-O bond distances are all of similar lengths [≈1.41(1) ?], and the O-C-O angles deviate from the ideal tetrahedral angle by a few degrees only.
- Spahr, Dominik,Binck, Jannes,Bayarjargal, Lkhamsuren,Luchitskaia, Rita,Morgenroth, Wolfgang,Comboni, Davide,Milman, Victor,Winkler, Bj?rn
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supporting information
p. 5419 - 5422
(2021/05/04)
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- Sr3[CO4]O Antiperovskite with Tetrahedrally Coordinated sp3-Hybridized Carbon and OSr6Octahedra
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We have synthesized the orthocarbonate Sr3[CO4]O in a laser-heated diamond anvil cell at 20 and 30 GPa by heating to ≈3000 (300) K. Afterward, we recovered the orthocarbonate with [CO4]4- groups at ambient conditions. Single-crystal diffraction shows the presence of [CO4]4- groups, i.e., sp3-hybridized carbon tetrahedrally coordinated by covalently bound oxygen atoms. The [CO4]4- tetrahedra are located in a cage formed by corner-sharing OSr6 octahedra, i.e., octahedra with oxygen as a central ion, forming an antiperovskite-type structure. At high pressures, the octahedra are nearly ideal and slightly rotated. The high-pressure phase is tetragonal (I4/mcm). Upon pressure release, there is a phase transition with a symmetry lowering to an orthorhombic phase (Pnma), where the octahedra tilt and deform slightly.
- Spahr, Dominik,K?nig, Jannes,Bayarjargal, Lkhamsuren,Gavryushkin, Pavel N.,Milman, Victor,Liermann, Hanns-Peter,Winkler, Bj?rn
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p. 14504 - 14508
(2021/10/01)
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- Nanostructuring of Strontium Hexaboride via Lithiation
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We describe the top-down nanostructuring of a metal boride using SrB6 as an example. To accomplish this transformation, we demonstrate (1) the direct lithiation of a metal boride using n-butyllithium and then (2) the reactive disassembly of Li-SrB6 into nanoparticles using water. The identity of the Li-SrB6 intermediate, a mixture of Li2B6, LixSr1-2xB6, and SrB6 phases, was established by powder X-ray diffraction (PXRD), solid-state 11B and 7Li NMR, transmission electron microscopy, selected-area electron diffraction, and scanning electron microscopy. The necessary 2Li+/Sr2+ substitution is enabled by cation mobility within the hexaboride lattice. The subsequent reaction with water results in Li2B6 decomposition and the release of 6 nanoparticles, which were characterized by PXRD, solid-state 11B and 7Li NMR, and high-resolution TEM. This chemistry opens new solution-based modification and processing options for metal borides.
- Ramachandran, Roshini,Salguero, Tina T.
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supporting information
p. 4 - 7
(2018/01/10)
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- Five heterometallic SrII-MII (M = Co, Ni, Zn, Cu) 3-D coordination polymers: Synthesis, structures and magnetic properties
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Five heterometallic coordination polymers based on pyridine 2,3-dicarboxylic acid (H2pydc), namely [MSr(pydc)2(H 2O)2]n (M = Co (1), Ni (2)), [MSr 2(pydc)3(H2O)4
- Chen, Yanmei,Gao, Qian,Zhang, Haifeng,Gao, Dandan,Li, Yahong,Liu, Wei,Li, Wu
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- Crystal growth of new hexahydroxometallates using a hydroflux
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A series of seven compounds, Sr2Mn(OH)6, Ba 2Mn(OH)6, Sr2Co(OH)6, Ba 2Co(OH)6, Sr2Ni(OH)6, Ba 2Ni(OH)6, and Ba2Cu(OH)6, were synthesized using a low-melting hydroflux, a hybrid approach between aqueous hydrothermal and molten hydroxide flux techniques. Crystals of the hexahydroxometallates were obtained by dissolving appropriate amounts of alkaline-earth nitrates or hydroxides and transition-metal oxides, acetates, or chlorides in the hydroflux and reacting at 180-230 C. The isostructural compounds all crystallize in the monoclinic space group P21/n. The monoclinic structure consists of isolated transition-metal octahedra within a three-dimensional framework of corner- and edge-shared eight-coordinate, alkaline-earth polyhedra. Magnetic susceptibility data show that all compounds are simple paramagnets. Thermogravimetric analysis indicates that these hydroxides lose water between 215 and 350 C and transform into oxide products, the identity of which depends on the metal cations present in the parent hexahydroxometallates.
- Chance, W. Michael,Bugaris, Daniel E.,Sefat, Athena S.,Zur Loye, Hans-Conrad
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p. 11723 - 11733
(2013/11/19)
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- Four alkali-induced 3d strontium(II) coordination polymers constructed from imidazole-4,5-dicarboxylate: Syntheses, crystal structures, and properties
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Four alkali-induced 3D coordination polymers, namely [Sr(HIDC)(H 3IDC)(H2O)]n·nH2O (1), [Sr(HIDC)]n (2), [Sr3(HIDC)2(H 2IDC)4]n (3), and [Sr2(HIDC) 2]n (4), were constructed from strontium(II) and imidazole-4,5-dicarboxylic acid (H3IDC) and were characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Complex 1 is an eca net with the Schlaefli symbol of (39.4 12.57) by considering the SrII cation as an 8-connected node. Complex 2 presents a rare 5-connected network with Schaefli symbol of (45.65) when the SrII cation and HIDC2- dianion are viewed as 5-connected nodes. Complex 3 is a complicated 3D network, which can be regarded as a H2IDC - monoanion sustained porous framework filled by another HIDC 2- dianion and H2IDC- monoanion. Complex 4 exhibits a 3D porous framework with 1D trigonal hydrophobic channels. The ligand H3IDC in the four complexes exists as the H3IDC molecule, the H2IDC- monoanion, and the HIDC2- dianion. In addition, the μ2 (κ1N:κ1O: κ1O) mode of the H3IDC molecule in complex 1, the μ3 (κ1O:κ1O: κ1O:κ1O) and μ3 (κ1N:κ1O:κ1O: κ1O) modes of the H2IDC- monoanion in complex 3, as well as the μ5 (κ1N: κ2O:κ1O:κ2O: κ1O) and μ6 (κ1N: κ2O:κ2O:κ2O: κ2O) modes of the HIDC2- dianion in complexes 2 and 4 are reported for the first time. Diverse topological architectures of the four complexes depend mainly on the coordination spheres of the SrII cation, the coordination modes of the anions, the different alkali, and the ligand to alkali ratio. TG analysis indicates that complex 2 presents high thermal stability, while the TG curve and temperature-dependent PXRD spectra of complex 4 indicate that its framework is stable up to 350 °C. Moreover, the solid-state luminescent properties demonstrate that complexes 1 to 4 exhibit strong blue emission at room temperature. Copyright
- Zhang, Xian-Fa,Deng, Zhao-Peng,Huo, Li-Hua,Feng, Qing-Mao,Gao, Shan
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p. 5506 - 5514
(2013/01/15)
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- Sr2GaScO5, Sr10Ga6Sc 4O25, and SrGa0.75Sc0.25O 2.5: A play in the octahedra to tetrahedra ratio in oxygen-deficient perovskites
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Three different perovskite-related phases were isolated in the SrGa 1-xScxO2.5 system: Sr2GaScO 5, Sr10Ga6Sc4O25, and SrGa0.75Sc0.25O2.5. Sr2GaScO 5 (x = 0.5) crystallizes in a brownmillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) A, b = 15.1594(1) A, and c = 5.70926(4) A] with complete ordering of Sc3+ and Ga 3+ over octahedral and tetrahedral positions, respectively. The crystal structure of Sr10Ga6Sc4O25 (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4 1/a, a = 17.517(1) A, c = 32.830(3) A]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr10Ga6Sc4O25 can be described as a stacking of eight perovskite layers along the c axis...[-(Sc/Ga)O1.6-SrO0.8-(Sc/Ga)O1.8- SrO0.8-]2.... Similar to Sr2GaScO5, this structure features a complete ordering of the Sc3+ and Ga 3+ cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr 10Ga6Sc4O25 is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc3+ by Ga3+ leads to the formation of the cubic perovskite phase SrGa0.75Sc0.25O 2.5 (x = 0.25) with a = 3.9817(4) A. This compound incorporates water molecules in the structure forming SrGa0.75Sc 0.25O2.5·xH2O hydrate, which exhibits a proton conductivity of ~2.0 × 10-6 S/cm at 673 K.
- Chernov, Sergey V.,Dobrovolsky, Yuri A.,Istomin, Sergey Ya.,Antipov, Evgeny V.,Grins, Jekabs,Svensson, Gunnar,Tarakina, Nadezhda V.,Abakumov, Artem M.,Van Tendeloo, Gustaaf,Eriksson, Sten G.,Rahman, Seikh M. H.
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p. 1094 - 1103
(2012/03/22)
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- Raman spectroscopic study of mixed carbonate materials
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The main parameters for precipitation of mixed carbonate materials have been studied by Raman microscopy. These carbonates are compounds of barium, strontium and calcium. It has been shown that the Raman spectrum of a sample is exclusively controlled by its composition, the precipitation parameters do not affect the crystal structure. Even at relatively low levels, the calcium content of a sample can dominate the vibrational frequencies as measured by Raman spectroscopy. Calcium contents greater than 17% show this effect to a considerable degree, and give the broadest or two Raman peaks and thus the least uniform unit cells. The analysis of the lattice modes demonstrates that each Raman shift observed for a mixed carbonate sample corresponds to a specific crystal structure. Some peaks lie within two or three shifts that are observed for different crystal structures.
- Kaabar,Bott,Devonshire
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p. 136 - 141
(2011/03/21)
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- Constitution of the Sr-Ni-O system
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The constitution of the Sr-Ni-O system was studied experimentally for the first time. Samples were prepared either from SrCO3 and NiO or from Sr(NO3)2 and Ni(NO3)2·6H 2O and characterized by high-temperature X-ray powder diffraction, scanning electron microscopy, thermogravimetric and differential thermal analyses. In the SrO-NiO quasibinary system an eutectic reaction: liquid?SrO+NiO was found to occur at 1396±5°C, while the homogeneity range of terminal solid solutions is negligible. Thermodynamic calculations using the regular solution model for the liquid and rocksalt-type phases were employed to predict liquidus and solidus curves. Three ternary compounds, SrNiO2.5, Sr5Ni4O11, and Sr9Ni7O21 were observed in the samples prepared from nitrate solutions, but only Sr9Ni7O21 was proved to be thermodynamically stable in air up to 1030±6°C. When heating in air, SrNiO2.5 and Sr5Ni4O 11 were found to transform irreversibly into a mixture of Sr 9Ni7O21 and NiO. Isothermal section of the SrO-NiO-O subsystem, which represents phase equilibria at 950-1030°C as well as an isobaric section of the Sr-Ni-O system in air were constructed.
- Zinkevich
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p. 2818 - 2824
(2008/10/09)
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- Phase equilibria in the pseudo-binary system SrO-Fe2O 3
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The phase relations in the pseudo-binary system SrO-Fe2O 3 have been investigated in air up to 1150°C by means of powder X-ray diffraction and thermal analysis. Sr3Fe2O 7-δ, SrFeO3-δ and Sr
- Fossdal, Anita,Einarsrud, Mari-Ann,Grande, Tor
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p. 2933 - 2942
(2008/10/09)
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- Desensitizing dental composition
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A dental composition for the treatment of dentinal hypersensitivity and in particular for the desensitization of exposed dentin, the desensitizing treatment of deep cavities, the desensitizing treatment when replacing dental layers, the stumps desensitizing treatment before placing dental prosthesis. The composition can be used as a solution or as a gel. In the first case two distinct liquid solutions for use successively on the exposed dentin are provided for. In the second case two distinct gel compounds spread successively on the exposed dentin are provided for. The first solution or the first gel compound comprises preferably three soluble potassium salts, whereas the second solution or the second gel compound comprises a calcium salt and a soluble strontium salt. In a preferred composition two solutions are provided for of which the first has solutes comprising potassium phosphate, potassium carbonate and potassium fluoride, and the second solution has solutes comprising calcium chloride and strontium chloride. For the gel composition, which may be used as toothpaste, two distinct gel compounds are provided, the first having solutes comprising potassium phosphate, potassium carbonate and potassium fluoride and the second gel compound having solutes comprising calcium chloride and strontium chloride.
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- Synthesis and characterization of nanosized SrBi2Ta2O9 powder by a novel sol-gel process
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Chemically homogeneous SrBi2Ta2O9 (SBT) sol was synthesized using ethoxy tantalum, strontium acetate, and bismuth subnitrate as starting materials, methoxyethylene as a solvent and acetic acid (HOAc) as a catalyst. Single-phased perovskite phase SBT ferroelectric ultrafine powder was obtained after the dried gel was treated at 350°C for 30min and calcined at 800°C for 1h. FT-IR, XRD, TEM and TG-DTA were employed to investigate the transformation processes of sol to gel and gel to ultrafine SBT powder. Acetic acid not only acts as an acid catalyst, but also changes the alkoxide precursor as a ligand at a molecular level. Bidentate acetates replace OR groups and are directly bounded to the tantalum, leading to the formation of Ta (OR)x(OAc)5-x. The perovskite SBT phase formed via intermediate phase Bi3TaO7 and a Bi-deficient pyrocholore phase.
- Wang, Wen,Jia, Dechang,Zhou, Yu,Ye, Feng
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p. 2517 - 2524
(2008/10/08)
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- Decomposition of the spin-1/2 Heisenberg chain compound SR2CuO3 in air and water: An EPR and magnetic susceptibility study of SR2Cu(OH)6
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The reaction of Sr2CuO3 with air and water was studied to address the origin of the reported variable Curie-Weiss impurity contribution to the magnetic susceptibility X of this compound at low temperatures. Sr2CuO3 was found to decompose upon exposure to either of these environments. The compound Sr2Cu(OH)6 was identified as the primary reaction product. A pure sample of Sr2Cu(OH)6 was then prepared separately. Electron paramagnetic resonance, isothermal magnetization versus magnetic field [M(H)], and X versus temperature T measurements demonstrate that Sr2Cu(OH)6 contains weakly interacting Cu2+ magnetic moments with spin S=1/2 and average g factor equal to 2.133. From a fit of X(T) by the Curie-Weiss law and of the M(H) isotherms by modified Brillouin functions, the exchange interaction between adjacent Cu2+ spins was found to be J/kB=1.06(4) K, a weakly antiferromagnetic interaction. Our results indicate that the previously reported, strongly sample-dependent, Curie-Weiss contribution to X(T) of a polycrystalline Sr2CuO3 sample most likely arises from exposing the sample to air, resulting in a variable amount of paramagnetic Sr2Cu(OH)6 on the surface of the sample.
- Hill, J. M.,Johnston, D. C.,Miller, L. L.
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- On Hydrated Strontium Hafnate
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For the first time, strontium hafnate of the composition SrHfO3 · 2H2O was isolated from hafnium-containing alkali solutions. This compound was the only solid product of the reaction in the range of the strontium-to-hafnium molar feed ratios studied from 0.52:1 to 1.74:1 under various synthesis conditions (T = 40-145°C, 50.0-67.0 wt % NaOH). The compound crystallizes in the cubic system with a varied within 4.072-4.144 A?. Water enters the compound as molecules or hydroxide groups and insignificantly influences its structure. Dehydration decreases a.
- Kostrikin,Spiridonov,Lin'ko,Ezhov,Kuznetsova,Martynova,Komissarova
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p. 639 - 641
(2008/10/08)
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