Lanthanum gallium tin antimonides LaGaxSnySb2

A series of quaternary lanthanum gallium tin antimonides LaGaxSnySb2 was elaborated to trace the structural evolution between the known end members LaGaSb2 (SmGaSb2-type) and LaSnySb2 (LaSn0.75Sb2-type). Five members of this series were characterized by single-crystal X-ray diffraction. For low Sn content, the Sn atoms disorder with Ga atoms in zigzag chains to form solid solutions LaGa1-ySnySb2 (0less than or equal toyless than or equal to0.2) adopting the SmGaSb2-type structure, as exemplified by LaGa0.92(3)Sn0.08Sb2 and LaGa0.80(3)Sn0.20Sb2 (orthorhombic, space group D-2(5) - C222(1), Z = 4). For higher Sn and lower Ga content, there is a segregation in which the Sn atoms appear in chains of closely spaced partially occupied sites as in the parent LaSn0.75Sb2-type structure whereas the Ga atoms remain in zigzag chains as in the parent SmGaSb2-type structure. This feature is observed in the structures of LaGa0.68(4)Sn0.31(3)Sb2, LaGa0.62(3)Sn0.32(3)Sb2, and LaGa0.43(3)Sn0.39(3)Sb2 (orthorhombic, space group D-2h(17) - Cmcm, Z = 4). The last example illustrates that the combined Ga/Sn content can be substoichiometric (x + y < 1). These compounds have a layered nature, with the chains of Ga or Sn atoms residing between (2)(infinity)[LaSb2] slabs. (C) 2002 Elsevier Science (USA).