Lanthanum Gallium Tin Antimonides LaGa xSn ySb 2

Abstract

A series of quaternary lanthanum gallium tin antimonides LaGa x Sn y Sb 2 was elaborated to trace the structural evolution between the known end members LaGaSb 2 (SmGaSb 2-type) and LaSn y Sb 2 (LaSn 0.75Sb 2-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 LaGa 1– y Sn y Sb 2 (0≤y≤0.2) adopting the SmGaSb 2-type structure, as exemplified by LaGa 0.92(3)Sn 0.08Sb 2 and LaGa 0.80(3)Sn 0.20Sb 2 (orthorhombic, space group D 5 2− 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 LaSn 0.75Sb 2-type structure whereas the Ga atoms remain in zigzag chains as in the parent SmGaSb 2-type structure. This feature is observed in the structures of LaGa 0.68(4)Sn 0.31(3)Sb 2, LaGa 0.62(3)Sn 0.32(3)Sb 2, and LaGa 0.43(3)Sn 0.39(3)Sb 2 (orthorhombic, space group D 17 2 h − 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 ∞[LaSb 2] slabs.