1993 年 42 巻 476 号 p. 484-489
The microstructure and optical properties of transparent glass-ceramics containing ZnAl2O4: Cr3+ have been examined by using X-ray diffraction, transmission electron microscopy and optical absorption measurement. The glass-ceramics were prepared by the heat treatment of glass with 20ZnO·20Al2O3·50SiO2·6TiO2·4ZrO2·0.1Cr2O3 composition (mol%). ZnAl2O4 and ZrTiO4 precipitated from the glass when the heat treatment temperature was above 850°C. The heat treatment below 1100°C successfully yielded the transparent glass-ceramics. The crystallite size of ZnAl2O4 increased from 5nm to 20nm as the heat treatment temperature was increased from 850°C to 1100°C. At 1100°C, the ZnAl2O4 crystallites precipitated as a cubic form. The optical absorption spectra at room temperature indicate that the absorption due to the 4A2→4T2 transition, which corresponds to the 10Dq, takes place at the wavelength of 650nm for the glass and at 557 to 530nm for the glass-ceramics. This fact suggests that the ligand field strength for the Cr3+ ion sites increases as the Cr3+ ions are incorporated into ZnAl2O4. The wavelength of the absorption band due to the 4A2→4T2 transition increases monotonically with an increase in crystallite size. This phenomenon is explaned by taking into account the surface state of fine. ZnAl2O4: Cr3+ particles and the variation of the concentration of Cr3+ ions in ZnAl2O4: Cr3+ with heat treatment temperature.