The growth of highly crystalline, idiomorphic potassium titanoniobate crystals by the cooling of a potassium chloride flux

Abstract

Highly crystalline, well-developed potassium titanoniobate (KTiNbO₅ and KTi₃NbO₉) crystals were successfully grown at temperatures ranging from 700 to 1000 °C by a KCl flux cooling method. Colourless and transparent KTiNbO₅ crystals with a smallest average size of 750 nm were grown at a relatively low temperature of 700 °C. The sizes of grown crystals were observed to greatly dependent on the holding temperature and solute concentration. HRTEM observations indicated that the flux-grown KTiNbO₅ crystals were of high quality. The band gap energies of the fabricated KTiNbO₅ and KTi₃NbO₉ crystals, as estimated from their absorption edges in UV-vis diffuse reflectance spectra, were approximately 3.54 and 3.35 eV, respectively. Furthermore, these crystals exhibited good photocatalytic activities under UV light irradiation. The photodecomposition of TCE gas occurred via a photocatalytic process under UV light irradiation. This study demonstrates that KCl flux cooling is an environmentally friendly and nature-mimetic process for growing high-quality, well-developed, and photocatalytic KTiNbO₅ and KTi₃NbO₉ crystals.