Zur Kenntnis der inversen Perowskite M3TO (M = Ca,Sr, Yb; T = Si,Ge, Sn,Pb)

On the Inverse Perovskites M₃TO (M = Ca, Sr, Yb; T = Si, Ge, Sn, Pb) Ca₃SiO and seven further inverse perovskites M₃TO (M = Ca, Sr, Yb; T = Si, Ge, Sn, Pb) were prepared in iron crucibles under argon by the reactions 6 M + TO₂ + T = 2 M₃TO, and 3 M+ TO = M₃TO for Yb₃PbO, respectively, at temperatures between 1123 to 1173 K. The crystal structures of all compounds were solved and refined using X—ray powder diffraction methods. Ca₃SiO, Ca₃GeO, Sr₃SiO, Sr₃GeO, Yb₃SiO and Yb₃GeO are orthorhombic perovskites (anti—GdFeO₃—type, space group Pbnm, No. 62, Z = 4). They show slightly distorted corner—sharing OM₆ octahedra that are tilted with respect to their positions in the ideal perovskite structure. The effective radii of the T^4— vary significantly with M²⁺. Thus, these perovskites can no longer be discussed in terms of the hard—sphere model, and Goldschmidt's tolerance factor does not apply. The ideal cubic representatives Yb₃SnO and Yb₃PbO were refined in space group Pm3¯m (anti—SrTiO₃ type, Z = 1).