材料期刊网

Large-sized (~2 inch, 50.8 mm) γ-LiAlO2 single crystal has been grown by conventional Czochralski (Cz) method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum (FWHM) values are 116.9 and 132.0~arcsec for transparent and milky parts, respectively. The vapor transport equilibrium (VTE) technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.