- SrP3N5NH: A Framework-Type Imidonitridophosphate Featuring Structure-Directing Hydrogen Bonds
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Nitridophosphates and imidonitridophosphates show intriguing structural diversity, including unprecedented structure types. Highly condensed strontium imidonitridophosphate SrP3N5NH has been synthesized at 8 GPa and 1100 °C using a high-pressure high-temperature approach starting from stoichiometric amounts of Sr(N3)2, P3N5 and NH4Cl. Herein, NH4Cl was used as a hydrogen source and as a precursor for in situ formation of SrCl2, which acts as mineralizer and facilitates growth of single-crystals with a diameter of ≤30 μm. SrP3N5NH (P21/c (no. 14), a=5.01774(2), b=8.16912(4), c=12.70193(5) ?, β=101.7848(3)°, Z=4) adopts an unprecedented network structure, represented by the point symbol (3.4.5.6.72)(3.4.5.72.8)(3.6.73.8). This unique three nodal P/N(H) network is stabilized by moderately strong hydrogen bonds causing a structure-directing effect, which has not yet been reported for imidonitridophosphates.
- Vogel, Sebastian,Schnick, Wolfgang
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- Crystalline Nitridophosphates by Ammonothermal Synthesis
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Nitridophosphates are a well-studied class of compounds with high structural diversity. However, their synthesis is quite challenging, particularly due to the limited thermal stability of starting materials like P3N5. Typically, it requires even high-pressure techniques (e.g. multianvil) in most cases. Herein, we establish the ammonothermal method as a versatile synthetic tool to access nitridophosphates with different degrees of condensation. α-Li10P4N10, β-Li10P4N10, Li18P6N16, Ca2PN3, SrP8N14, and LiPN2 were synthesized in supercritical NH3 at temperatures and pressures up to 1070 K and 200 MPa employing ammonobasic conditions. The products were analyzed by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and FTIR spectroscopy. Moreover, we established red phosphorus as a starting material for nitridophosphate synthesis instead of commonly used and not readily available precursors, such as P3N5. This opens a promising preparative access to the emerging compound class of nitridophosphates.
- Mallmann, Mathias,Schnick, Wolfgang,Wendl, Sebastian
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- Nitridophosphate-Based Ultra-Narrow-Band Blue-Emitters: Luminescence Properties of AEP8N14:Eu2+ (AE=Ca, Sr, Ba)
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The nitridophosphates AEP8N14 (AE=Ca, Sr, Ba) were synthesized at 4–5 GPa and 1050–1150 °C applying a 1000 t press with multianvil apparatus, following the azide route. The crystal structures of CaP8N14 and SrP8N14 are isotypic. The space group Cmcm was confirmed by powder X-ray diffraction. The structure of BaP8N14 (space group Amm2) was elucidated by a combination of transmission electron microscopy and diffraction of microfocused synchrotron radiation. Phase purity was confirmed by Rietveld refinement. IR spectra are consistent with the structure models and the chemical compositions were confirmed by X-ray spectroscopy. Luminescence properties of Eu2+-doped samples were investigated upon excitation with UV to blue light. CaP8N14 (λem=470 nm; fwhm=1380 cm?1) and SrP8N14 (λem=440 nm; fwhm=1350 cm?1) can be classified as the first ultra-narrow-band blue-emitting Eu2+-doped nitridophosphates. BaP8N14 shows a notably broader blue emission (λem=417/457 nm; fwhm=2075/3550 cm?1).
- Wendl, Sebastian,Eisenburger, Lucien,Strobel, Philipp,Günther, Daniel,Wright, Jonathan P.,Schmidt, Peter J.,Oeckler, Oliver,Schnick, Wolfgang
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p. 7292 - 7298
(2020/05/18)
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- Electronic and ionic conductivity in alkaline earth diazenides M AEN2 (MAE = Ca, Sr, Ba) and in Li 2N2
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Electrical conductivity measurements of alkaline earth diazenides SrN 2 and BaN2 revealed temperature-dependent metal-like behavior. As CaN2 is isotypic with SrN2 its electronic properties are supposed to show similar characteristics. For the alkali diazenide Li2N2, the corresponding measurement shows not only the typical characteristics of metallic materials but also an unexpected rise in electrical conductivity above 250 K, which is consistent with an ionic contribution. This interpretation is further corroborated by static 6Li and 7Li nuclear magnetic resonance measurements (NMR) of the spin-lattice relaxation time (T1) over an extended temperature range from 50 to 425 K. We observe a constant Heitler-Teller product (T 1T) as expected for metals at low temperatures and a maximum in the temperature-dependent relaxation rates, which reflects the suggested ionic conductivity. A topological structural analysis indicates possible 3D ion migration pathways between two of the three crystallographic independent Li positions. A crude estimate of temperature-dependent self-diffusion coefficients D(T) of the lithium motion classifies Li2N2 as a mixed electronic/ionic conductor.
- Schneider, Sebastian B.,Mangstl, Martin,Friederichs, Gina M.,Frankovsky, Rainer,Schmedt Auf Der Guenne, Joern,Schnick, Wolfgang
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p. 4149 - 4155
(2013/12/04)
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- Synthesis of alkaline earth diazenides MAEN2 (M AE = Ca, Sr, Ba)by Controlled Thermal Decomposition of Azides under High Pressure
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The alkaline earth diazenides MAEN2 with M AE = Ca, Sr andBa were synthesized by a novel synthetic approach, namely, a controlleddecomposition of the corresponding azides in a multianvil press at highpressure/high-temperature conditions. The crystal structure of hithertounknown calcium diazenide (space group I4/mmm (no. 139), a = 3.5747(6)A, c = 5.9844(9)A, Z = 2, wRp = 0.078)was solved and refined on the basisof powder X-ray diffraction data as well as that of SrN 2 and BaN2.Accordingly, CaN2 is isotypic with SrN2 (space group I4/mmm (no. 139), a =3.8054(2)A, c = 6.8961(4)A, Z = 2, wRp = 0.057)and the correspondingalkaline earth acetylenides (MAEC2)crystallizing in a tetragonally distortedNaCl structure type. In accordance with literature data, BaN2 adopts a moredistorted structure in space group C2/c (no. 15)with a = 7.1608(4)A, b =4.3776(3)A, c = 7.2188(4)A, β = 104.9679(33)°, Z = 4 and wRp = 0.049).The N-N bond lengths of 1.202(4)A in CaN2 (SrN2 1.239(4)A, BaN21.23(2)A)correspond well with a double-bonded dinitrogen unit confirming a diazenide ion [N 2]2-. Temperature-dependent insitu powder X-ray diffractometry of the three alkaline earth diazenides resulted in formation of the corresponding subnitridesMAE2N (MAE = Ca, Sr, Ba)at higher temperatures. FTIR spectroscopy revealed a band at about 1380 cm-1 assigned to the N-Nstretching vibration of the diazenide unit. Electronic structure calculations support the metallic character of alkaline earthdiazenides.
- Schneider, Sebastian B.,Frankovsky, Rainer,Schnick, Wolfgang
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p. 2366 - 2373
(2012/04/18)
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- High-Pressure synthesis of BaSr2P6N12 and BaCa2P6N12 and comparison of the structures of BaP2N4, BaCa2P6N12, and BaSr2P6N12
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The novel nitridophosphates BaCa2P6N12 and BaSr2P6 N12 were obtained by means of high-pressure high-temperature synthesis utilizing the multianvil technique (1200°C, 5 GPa). The complex anion [PN2-] of the title compound is formally isoelectronic with silica. The crystal structure was solved from powder data and refined by the Rietveld method (BaCa 2P6N12: Pa3, Z = 4, a = 9,9578(2) A; BaSr2P6N12: Pa3, Z = 4, 10,0705(2) A). The crystal structures are derived from that of BaP2N4 which is isotypic with a high pressure phase of CaB2O4 and BaGa2S4. For each compound the 31P solid state NMR spectrum yielded a single resonance (BaCa2P6N 12: 7.4 ppm; BaSr2P6N12:3.9 ppm).
- Karau, Friedrich,Schnick, Wolfgang
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p. 231 - 237
(2008/10/09)
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- Azides and Cyanamides - Similar and Yet Different
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The crystal structures of LiN3*;H2O (P6 3/mcm (No. 193), Z = 6; 924.01(13); 560.06(7) pm); NH 4N3 (Pmna (No. 53), Z = 4; a = 889.78(18), b = 380,67(8), c = 867.35(17) pm); Ca(N3)2 (Fddd (No. 70), Z = 8; a = 595.4(2), b = 1103.6(5), c = 1133.1(6) pm), Sr(N3)2 (Fddd(No. 70), Z = 8; a = 612.02(9), 6 = 1154.60(18), c = 1182.62(15) pm); Ba(N3)2 (P21/m (No. 11), Z = 2; a = 544.8(1), b = 439.9(1), c = 961.3(2) pm, β = 99.64(3)°) and TIN3 (I4/mcm (No. 140), Z = 2; 618.96(9); 732.71(15) pm) have been either determined for the first time or redetermined by X-ray diffraction on single crystals. The afore mentioned compounds, AN3 (A = Na, K, Rb, Cs), M(N 3)2 · 2.5 H2O (M = Mg, Zn) and the cyanamides Li2CN2, CdCN2 and CuCN2 were investigated by Raman and IR spectroscopy (KBr technique). Structural features and spectroscopic data of azides and cyanamides from this work and from literature are listed and compared.
- Reckeweg, Olaf,Simon, Arndt
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p. 1097 - 1104
(2007/10/03)
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