The thermal and optical properties of BaWO4 single crystal

In this paper, barium tungstate single crystal grown by the Czochralski method was reported. The structure of BaWO4 crystal was characterized by X-ray powder diffraction (XRPD) and the result shows that BaWO4 crystal belongs to the scheelite structure. Subsequently, its thermal and optical properties were studied by measuring the thermal expansion, specific heat and transparence spectra. These results show that BaWO4 crystal possesses large anisotropic thermal expansion and its thermal expansion coefficients are αa=4.8×10-6/K, αb=5.1×10-6/K and αc=2.3×10-5/K from 298.15 to 573.15 K, respectively. The reason for large anisotropic thermal expansion coefficients along different crystallographic axes was discussed according to the structure of BaWO4 crystal. The measured specific heat value is 0.31-0.36 Jg−1 K−1 in the temperature range of 336.15-573.15 K, and the result is in consistent with the value calculated according to Dulong-Petit law of specific heat. The impact of large anisotropic thermal expansion on crystal growth and processing was also discussed. The cutoff wavelength of BaWO4 crystal is 255 nm and the optical transparency range is 255-3700 nm at room temperature.