Abstract
The first results for growth of germanium dioxide single crystals with the crquartz type structure (α-GeO2) from refluxed hydrothermal solutions are reported. The success of this method is due to the existence of metastable α-GeO2 in aqueous solutions at relatively low temperature and to the structural similarity between α-GeO2 and α-SiO2. The continuous partial evaporation of the heated solvent, vapour condensation, saturation of the condensate by nutrient α-GeO2 and growth of α -GeO2 single crystals on quartz seeds are considered as the successive stages of the process. Mzre homogeneous crystals of α -GeO2 were obtained on seeds parallel to {0001}, {1120} and {1121} faces using sodium hydroxide and ammonium fluoride solutions in the range of temperature 90-130°C and at pressure equivalent to the fugacity of saturated vapor.
Piezoelectric, elastic and dielectric properties of the mentioned above crystals for the first time were studied.