X-ray Diffraction Study of Mixed-Layer Compounds in the Pseudobinary System SnTe–Bi2Te3

X-ray diffraction studies of cleaved single-crystal specimens and powders demonstrate that the SnTe–Bi₂Te₃ system contains a homologous series of nSnTe · mBi₂Te₃ layered compounds (n = 1, 2; m = 1–3). In addition to the known compound SnBi₂Te₄, the compounds SnBi₄Te₇ (n = 1, m = 2) and SnBi₆Te₁₀ (n = 1, m= 3), structural analogues of GeBi₄Te₇ and GeBi₆Te₁₀, are identified. SnBi₄Te₇ has a 12-layer structure with lattice parameters a = 0.4392(1) nm andc = 2.399(1) nm (sp. gr. P m1). SnBi₆Te₁₀ has a 51-layer structure with a= 0.4391(1) nm and c= 10.264(5) nm (sp. gr. R m). The new structural data for nSnTe · mBi₂Te₃ compounds and earlier results are used to reassess the SnTe–Bi₂Te₃ phase diagram.     

Homologous series of layered tetradymite-like compounds in the Sb-Te and GeTe-Sb2Te3 systems

The structures of layered compounds in thenSb₂ ·mSb₂Te₃ andnGeTe ·mSb₂Te₃ homologous series were studied by x-ray diffraction. GeSb₆Te₁₀ (n = 1,m = 3) was shown to have a 51-layer structure (sp. gr. ) withc = 10.202(1) nm. In the structure of GeSb₆Te₁₀, Sb₂Te₃ five-layer slabs and GeSb₂Te₄ sevenlayer slabs are stacked along thec axis in the ordered sequence -557 557 557-. Crystallographic data for this compound are presented. The specific and common structural features of the layered compounds in thenSb₂ ·mSb₂Te₃ andnGeTe ·mSb₂Te₃ homologous series are discussed.