SYNTHESIS OF POTASSIUM NIOBATE FROM METAL ALKOXIDES

Preparation of potassium niobate from metal alkoxides was investigated. Potassium-niobium ethoxide, KNb(OC2H5)6, and potassium-niobium propoxide, KNb(OC3H7)6, were synthesized and subsequently hydrolyzed using several water concentrations (0.75 to 6.0 mol of water/(mol of alkoxide)). Rapid precipitation of potassium-deficient particles occurred when higher concentrations of water were used. This resulted in the formation of a multiphase material after calcination, as X-ray diffraction showed the presence of both KNbO3 and potassium-deficient oxide phases(s). Single-phase KNbO3 could be prepared by two methods: (1) hydrolysis of KNb(OC3H7)6/propanol solutions using 1 mol of water (per mole of propoxide) added as a water/propanol solution and (2) hydrolysis of KNb(OC2H5)6/ethanol solutions using 1 mol of water (per mole of ethoxide) added as a water/methanol solution. The latter method provided advantages of low calcination temperature for the formation of single-phase KNbO3 and low weight loss after calcination.