Growth of KNbO3 Single Crystals by the Flux Method Using KBO2 as a Flux

KNbO3 single crystals are grown by the self-flux method using K2CO3 as a flux, but often suffer from discolouration. In this work, KNbO3 single crystals were grown by the flux method using KBO2 as a flux. KNbO3 powder was prepared by the solid-state reaction of K2CO3 and Nb2O5. KBO2 was fabricated by the reaction of K2B4O7·4H2O and K2CO3. Single crystals of KNbO3 were grown in a Pt crucible and the structure and dielectric properties of the single crystals were investigated. X-ray diffraction showed the KNbO3 single crystals to have an orthorhombic Cmm2 perovskite unit cell at room temperature. The existence of ferroelastic domains was revealed by transmission electron microscopy. Electron probe microanalysis showed the single crystals to be stoichiometric and contain small amounts of B. Differential thermal analysis, Raman scattering and impedance spectroscopy were used to study the phase transitions. KBO2 may be a suitable flux for the growth of KNbO3 single crystals.