Abstract
Hydrothermal reactions of commercial Nb 2O 5 with aqueous MOH, M=Na, K, at 200 °C and autogenic pressure provided new routes to different niobium compounds. The reaction of Nb 2O 5 with NaOH was used to synthesize NaNbO 3 under mild conditions. The known room-temperature phase was obtained and identified by infrared spectroscopy and X-ray powder diffraction. In similar conditions, reactions of Nb 2O 5 with KOH yielded alkaline aqueous solutions containing soluble potassium hexaniobates. Those solutions were used to prepare K 6H 2[Nb 6O 19]·13H 2O and niobic acid. Hydrothermal reactions of commercial Nb 2O 5 with aqueous MOH, M=Na, K, provided thus a more convenient process of attack to niobium pentoxide than the traditional method of fusion of mixtures of the niobium oxide with alkali metal hydroxides or carbonates.
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