Formation of MgGeO3 from the hydrate prepared by hydrolysis of magnesium and germanium oxides

Abstract

Magnesium–germanium hydrate, which yields a MgGeO₃ powder, has been prepared by the simultaneous hydrolysis of magnesium and germanium alkoxides. Its composition is MgGeO₃·0.25H₂O·nH₂O, and its structure is similar to that of Mg₃Si₄O₁₀(OH)₂·nH₂O and 4.25MgO·4GeO₂·1H₂O·5H₂O prepared hydrothermally. Magnesium metagermanate, MgGeO₃, is slowly crystallized at 660–1 200 °C after the completion of dehydration of the hydrate. The kinetics of crystallization of MgGeO₃ have been studied by means of X-ray diffraction measurements. The initial stage at each temperature proceeds rapidly. The final stages can be expressed in terms of the contracting cube equation, the activation energy being 198 kJ mol^–1.