Transparent glass-ceramics containing LiGa5O8:CO2+ have been prepared by heat treatment of glass with a composition of 13Li2O.23Ga2O3.64SiO2.XCOO (0.1, 0.2, 0.5, 1.0) (mol%). The microstructure and the optical properties have been examined by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and optical absorption measurements. XRD analyses indicated that LiGa,508 microcrystals with a crystallite size of 5 to 10 nm precipitated in the specimens heat-treated at temperatures between 750 and 850-degrees-C. Above 850-degrees-C, LiGaSi2O6 crystals also precipitated. Heat treatment below 850-degrees-C successfully yielded transparent glass-ceramics. The optical absorption spectra at room temperature indicated that the absorption band due to the 4A2 --> 4T1(P) transition of Co2+ ions in tetrahedral sites showed three peaks (520, 586 and 686 nm) for the glass and three peaks (560, 597, and 646 nm) for the glass-ceramics. This difference in the spectra suggests that some Co2+ ions replaced the Ga3+ ions in tetrahedral sites of the LiGa5O8 microcrystals.
