Synthese und Kristallstruktur von zwei Bariumtitanplatinoxiden Ba(Ti,Pt)O₃ und Ba₄(Ti,Pt)₂²PtO₁₀

Abstract

Synthesis of two barium titanium platinum oxides gave hexagonal crystals of composition Ba(Ti_0.88Pt_0.12)O₃ [space group: P6₃/mmc; Z = 6; a₀ = 5.723(1) Å, c₀ = 14.023(1) Å] and orthorhombic Ba₄(Ti_1.81Pt_0.19)PtO₁₀ [space group: Cmca; Z = 4; a₀ = 5.783(1) Å, b₀ = 13.368(2) Å, c₀ = 13.129(1) Å]. A refinement of the atomic parameters of Ba(Ti,Pt)O₃ gave a R-value of 0.021 for 309 observed reflections. The crystal structure of Ba₄(Ti,Pt)₂PtO₁₀ could be refined to R = 0.037 for 1026 observed reflections. Both crystal structures can be described as a close-packed arrangement of barium and oxygen atoms with titanium and platinum in octahedral voids. The sequence of layers in the hexagonal compound is ABACBC along [001], the crystal structure of Ba₄(Ti,Pt)₂PtO₁₀ contains a hexagonal sequence of eight layers along [0[unk]1] with some positions of the close-packed arrangement not occupied. Distances between central cations in double or triple groups of face-sharing octahedra are significantly shorter than in other barium titanates. This is probably due to the substitution of titanium by transition elements.