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.
