Barium germanate

Description

Barium germanate can be formed by firing the oxides together at about 750–800°C: BaO + GeO2?BaGeO3 The metagermanate results. This salt is dimorphic and forms both α- and β-BaGeO3. β-BaGeO3 is a pseudo-wollastonite which transforms at 1225°C to α-BaGeO3. The former consists of digermanate groups arranged in a chain structure.
The structure consists of alternating layers of Ba cations and triangular [GeO3]3 rings, and is closely related to pseudo-wollastonite. The rings show a twofold positional disorder owing to stacking faults. The stacking is not random, but can be rationalized by a twinning mechanism mapping the two noncongruent enantiomorphic polytypes of the structure onto each other. The compound is monoclinic with space group C2/c and unit-cell parameters of a = 13.1877 ? , b = 7.6222 ? , c = 11.7190 ? , b = 112.295° , V = 1089.9 ?³ and Z = 12.