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The first results for growth of germanium dioxide single crystals with the crquartz type structure (a-GeOz) from refluxed hydrothermal solutions are reported. "he success of this method is due to the existence of metastable a-GeOz in aqueous solutions at relatively low temperature and to the structural similarity between a-GeO2 and a-SiOz. The continuous partial evaporation of the heated solvent, vapour condensation, saturation of the condensate by nutrient a-GeOz and growth of a-GeOz single crystals on quartz seeds are considered as the successive stages of the process. Mzre homogeneous crystals of a-GeO2 were obtained on seeds parallel to {OOOl}, (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 6rst time were studied.

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