- Crystal growth and characterization of Eu2+ doped Cs1-xRbxCaBr3
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A series of Eu2+ doped Cs1-xRbxCaBr3 solid solutions were grown using the Bridgman-Stockbarger technique. Their photoluminescence and scintillation properties are studied. Upon optical and X-ray excitation, the Cs1-xRbxCaBr3 and Eu2+ activated samples show a band, which can be attributed to the 5d-4f transition in Eu2+. The decay time constants become shorter with increasing Rb content and lie in the range of 3–4 μs. The scintillation performance of solid solutions Cs1-xRbxCa0.95Eu0.05Br3 is improved compared with the end members (CsCa0.95Eu0.05Br3 and RbCa0.95Eu0.05Br3). The best energy resolution of 6.4% at 662 keV was determined for Cs0.2Rb0.8Ca0.95Eu0.05Br3, and the best light yield, equal to 61.2% of NaI:Tl, was demonstrated by Cs0.4Rb0.6Ca0.95Eu0.05Br3.
- Rebrova,Grippa, A.Yu.,Boiaryntseva,Berastegui,Gorbacheva,Pedash, V.Yu.,Galkin,Kononets,Datsko, Yu.N.,Cherginets
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- Influence of hidden halogen mobility on local structure of CsSn(Cl1?xBrx)3mixed-halide perovskites by solid-state NMR
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Tin halide perovskites are promising candidates for lead-free photovoltaic and optoelectronic materials, but not all of them have been well characterized. It is essential to determine how the bulk photophysical properties are correlated with their structures at both short and long ranges. Although CsSnCl3is normally stable in the cubic perovskite structure only above 379 K, it was prepared as a metastable phase at room temperature. The transition from the cubic to the monoclinic phase, which is the stable form at room temperature, was tracked by solid-state133Cs NMR spectroscopy and shown to take place through a first-order kinetics process. The complete solid solution CsSn(Cl1?xBrx)3(0 ≤x≤ 1) was successfully prepared, exhibiting cubic perovskite structures extending between the metastable CsSnCl3and stable CsSnBr3end-members. The NMR spectra of CsSnBr3samples obtained by three routes (high-temperature, mechanochemical, and solvent-assisted reactions) show distinct chemical shift ranges, spin-lattice relaxation parameters and peak widths, indicative of differences in local structure, defects and degree of crystallinity within these samples. Variable-temperature119Sn spin-lattice relaxation measurements reveal spontaneous mobility of Br atoms in CsSnBr3. The degradation of CsSnBr3, exposed to an ambient atmosphere for nearly a year, was monitored by NMR spectroscopy and powder X-ray diffraction, as well as by optical absorption spectroscopy.
- Karmakar, Abhoy,Bhattacharya, Amit,Sarkar, Diganta,Bernard, Guy M.,Mar, Arthur,Michaelis, Vladimir K.
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- Hydrothermal Crystal Growth of Mixed Valence Cs2SbBr6
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Mixed valence perovskite materials present an opportunity to understand how structural motifs influence electronic properties in semiconducting materials. Here, we report the preparation of high-quality single crystals of the mixed valence compound Cssub
- Combs, Victoria E.,Oswald, Iain W. H.,Neilson, James R.
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- Time-dependent transformation routes of perovskites CsPbBr3and CsPbCl3under high pressure
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All-inorganic halide perovskites are prospective materials for diverse applications in photovoltaic and optoelectronic devices. Their high performance is associated with good operational stability, which is the key problem of hybrid organic-inorganic perovskites. However, for these materials only fragmentary information is available on the mechanical robustness and response to external stress, fundamentally important for strain engineering in multilayers, pressure-assisted technologies, and flexible panels applications. Here we show that all-inorganic perovskites CsPbX3 (where X = Cl, Br) undergo various types of pressure-induced transformations, including reversible phase transitions, irreversible chemical reactions reducing the dimensionality of PbX6 frameworks, and amorphization. The transformation routes depend on the mode of the applied stress and are related to the kinetics of transitions to the most stable phases. The slow-kinetics transformations in a moderate pressure range of technological importance, between 0.5 and 1.5 GPa, can require days or even weeks, depending on the sample quality and external stimuli. The pressure-induced narrowing and widening of energy gaps has been explained by the mechanism combining Pb-X bond lengths and PbX6 octahedra tilts with the electronic structure of the crystals.
- Katrusiak, Andrzej,St?hl, Kenny,Szafrański, Marek
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p. 10769 - 10779
(2021/05/14)
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- Ion Exchange of Layered Alkali Titanates (Na2Ti3O7, K2Ti4O9, and Cs2Ti5O11) with Alkali Halides by the Solid-State Reactions at Room Temperature
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Ion exchange of layered alkali titanates (Na2Ti3O7, K2Ti4O9, and Cs2Ti5O11) with several alkali metal halides surprisingly proceeded in the solid-state at room temperature. The reaction was governed by thermodynamic parameters and was completed within a shorter time when the titanates with a smaller particle size were employed. On the other hand, the required time for the ion exchange was shorter in the cases of Cs2Ti5O11 than those of K2Ti4O9 irrespective of the particle size of the titanates, suggesting faster diffusion of the interlayer cation in the titanate with lower layer charge density.
- Ogawa, Makoto,Saothayanun, Taya Ko,Sirinakorn, Thipwipa Tip
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p. 4024 - 4029
(2020/04/08)
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- Composition related structural transition between mechanosynthesized CsPbBr3 and CsPb2Br5 perovskites and their optical properties
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A facile solvent-free mechanochemical synthesis mechanism of perovskites of Cs–Pb–Br system has been demonstrated in the present study. Inherent structural and microstructural characteristics of CsPbBr3 and CsPb2Br5 perovskites are investigated by analyzing powder XRD patterns using Rietveld refinement analysis and formation of these perovskites has been ascertained. The compositional phase transition between orthorhombic CsPbBr3 and tetragonal CsPb2Br5 perovskites has been explained from the structural point of view. The optically active orthorhombic CsPbBr3 perovskite transforms to optically inactive tetragonal CsPb2Br5 perovskite under flowing water vapour within a short duration and the reverse transformation is noticed when the tetragonal perovskite is heat-treated at elevated temperature. Optical properties of these perovskites corroborate well with structural phase transitions of these compounds. This new approach of structural conversion not only provides a controlled synthesis of the ternary Cs–Pb–Br system but also demonstrates a clear underlying mechanism for the structural instability and associated optical properties.
- Maity,Pradhan
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- Synthesis and Crystal Structure of Cs3(AuBr4)2Br3
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Cs3(AuBr4)2Br3 is obtained in the form of red needles by adding the stoichiometric amount of CsBr to a solution of HAuBr4 and Br3(1-) in aqueous HBr.The salt decomposes slowly at room temperature to form a mixed-valent, cubic bromo aurate(I,III), in which the linear AuBr2(1-) ions are partially substituted by Br3(1-) ions.At 140 deg C Cs2Au2Br6 and CsBr are formed.Cs3(AuBr4)2Br3 crystallizes monoclinic with four formula units in the space group P21/c.The structure is built up by AuBr4(1-) and Br3(1-) anions and Cs(1+) cations.An average Au-Br distance of 242.2 pmwas found for the square planar AuBr4(1-) ion.The linear Br3(1-) groups are almost symmetrical with Br-Br distances of 254.0 and 256.2 pm.Therefore only two vibrations are observed in the IR spectrum: νas=172, δ=56 cm-1.The absorptions of the AuBr4(1-) groups are: νas=250, δas=113, γ=102 cm-1.Keywords: Synthesis, IR Spectra, Crystal Structure
- Lehnis, Birgit,Straehle, Joachim
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p. 1504 - 1508
(2007/10/02)
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