Growth of MgTa2O6 single crystals by floating zone method and their optical properties

MgTa2O6 single crystals, which adopt trirutile structure, were successfully grown by a floating zone method, and their optical properties were investigated. The as-grown crystals were black and opaque, but subsequent annealing in air from 1200° to 800°C rendered the crystals pale-yellow and transparent. The refractive indices for ordinary and extraordinary rays were 2.07 and 2.18 under white light, respectively, and the birefringence was 0.11. The interference figure observed with a polarizing microscope was typical one for an optically uniaxial crystal, which indicates that the crystal was optically uniform. Transmittance in the wavelength range of 500 to 2000 nm was about 75%, which approximately corresponded to the theoretical value calculated from the refractive index. The absorption edge of MgTa2O6 was at 290 run.