Characterization of KNbO₃ Particles Prepared by Heating of Complex between Nb-peroxo Compound and K ion

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The complex between the Nb-peroxo compound and KNO₃ was prepared by heating the Nb-peroxo compound aqueous solution with KNO₃ at 573 K for 1 h. The single phase of KNbO₃ was obtained by firing the complex between the Nb-peroxo compound and KNO₃ at 873 K for 2 h. The obtained KNbO₃ had tetragonal crystal system. On the other hand, when the stoichiometric mixed powder of Nb₂O₅ and K₂CO₃ with the molar ratio of Nb : K=1 : 1 was fired at 873 K for 2 h, orthorhombic KNbO₃ was obtained. In general, tetragonal phase can be obtained under high pressure condition at more than 6.6 GPa. When the complex between the Nb-peroxo compound and KNO₃ was used for the KNbO₃ preparation, the tetragonal KNbO₃ was obtained at normal pressure condition. The lattice parameter of a axis of the KNbO₃ obtained from the Nb-peroxo compound solution was less than that of the stoichiometric one. According to this fact and the result of UV-VIS spectra, the KNbO₃ prepared by firing the complex between the Nb-peroxo compound and KNO₃ had oxygen vacancies, which affected the lattice parameter and the crystal system.