Cs1−xSn1−x Bi9+xSe15 and Cs1.5−3xBi9.5+xSe15 : members of the homologous superseries Am[M1+lSe2+l] 2m[M1+2l+nSe3+3l +n] (A = alkali metal, M = Sn and Bi) allowing structural evolution in three different dimensions
Abstract
Cs1−xSn1−x Bi9+xSe15 and Cs1.5−3xBi9.5+xSe15 crystallize in a new structure type which does not belong to but is closely related to the members of the homologous series Am[M6- Se8]m[M5+nSe9+ n]; the new phases reveal a third dimension of structural evolution for this series according to the formula Am[M1+lSe2+l] 2m[M1+2l + nSe3+3l+n].