Structure Modification on Quaternary Rare Earth Thiophosphates: NaYbP2S6, NaSmP2S6, and KSmP2S7
2001; Elsevier BV; Volume: 160; Issue: 1 Linguagem: Inglês
10.1006/jssc.2001.9222
ISSN1095-726X
AutoresEun-Young Goh, Eun Jeong Kim, Sung Jin Kim,
Tópico(s)Inorganic Chemistry and Materials
ResumoThree rare earth quaternary compounds, NaYbP2S6, NaSmP2S6, and KSmP2S7, are synthesized using alkali metal halide or polychalcogenides flux. NaYbP2S6 was prepared from the stoichiometric reaction of Yb/S/P/NaCl flux at 700°C, and NaSmP2S6 and KSmP2S7 were prepared from Sm/S/P/Na2S (K2Sx) flux at 750°C. The structures were determined by the single-crystal X-ray diffraction technique. The air-sensitive dark-red crystals of NaYbP2S6 crystallize in the triclinic space group P-1 with a=6.8241(10) Å, b=7.0371(10) Å, c=9.107(2) Å, α=87.17(2)°, β=87.62(2)°, γ=88.30(2)°, and Z=2. The yellow plate crystals of NaSmP2S6 crystallize in the monoclinic space group P21/a with a=11.0717(10) Å, b=7.2999(1) Å, c=11.579(3) Å, β=111.30(2)°, and Z=4. The pale yellow plate crystals of KSmP2S7 crystallize in the monoclinic space group P21/a with a=8.981(2) Å, b=12.254(2) Å, c=9.609(1) Å, β=90.27(2)°, and Z=4. NaYbP2S6 and NaSmP2S6 are derivatives of the MIMIIIP2S6 family. NaYbP2S6 has a flat monolayered structure, and there are weak interactions between neighboring layers. In NaSmP2S6, two MPS3-type layers are condensed together. The ordering features of sodium and rare earth metal cations in two-dimensional layers are different: Na and Yb atoms are arranged in pairing fashion in NaYbP2S6, while Na and Sm atoms are arranged in a triangular pattern in NaSmP2S6. The structure of KSmP2S7 is similar to that of ABiP2S7 (A=K, Rb), where corrugated layers are formed from Sm3+ and [P2S7]4− units. The optically measured band gaps of NaYbP2S6 and NaSmP2S6 are 1.85 eV and 2.54 eV, respectively.
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