Growth, defects, mechanical, and optical properties of transparent KTaO3 single crystal

KTaO3 (KT) is an important material for optoelectronic and tunable microwave applications. However, growing large size and uniform crystals still remain a challenge. In this paper, a promising approach for growing relatively large size and high-quality KT single crystal was explored, and a transparent KT single crystal with dimension of CYRILLIC CAPITAL LETTER EF 30 x 80 mm, weighing as much as 406 g, was grown by Czochralski method successfully. The full width at half maximums (FWHMs) of X-ray rocking curves (XRCs) are 0.016 degrees, 0.011 degrees, and 0.016 degrees, respectively, implying that the KT crystal possesses high crystalline quality. A comprehensive investigation of its mechanical, thermal, and optical properties was carried out. The Mohr's hardness is obtained to be 6.0, indicating that the KT is more conducive to being processed compared with diamond. The Sellmeier equation is fitted and the refractive index curve in the range of 400-3000 nm is displayed based on the measured refractive index. All results are of great significance for the further research and application of KT crystal.