Morphology controls of GeO₂ particles precipitated by a facile acid-induced decomposition of germanate ions in aqueous medium

GeO₂ single crystals with various morphologies were synthesized at room temperature by an acid-induced homogenous liquid phase precipitation technique without using any surfactants as studied previously. With addition of aqueous ammonia, the solubility of hexagonal GeO₂ in water was significantly increased by formation of soluble germanate ions as confirmed by IR spectra analyses. Supersaturated GeO₂ solution could be produced by adding acid into the GeO₂-ammonia solution through the acid-induced transformation of germinate ions into GeO₂. GeO₂ spheres were obtained with phosphoric acid addition. Truncated cubic-like and cubic-like GeO₂ single crystals could be produced in the solutions with hydrochloric acid and ascorbic acid (vitamin C) additions, respectively. The morphology developments of the GeO₂ particles induced by various acids were discussed and the growth mechanism conforms to BFDH and HP crystal growth models.