Spectroscopic properties of Co2+ ions in La2O3–MgO–Al2O3–SiO2 glass-ceramics

Co2+-doped La2O3–MgO–Al2O3–SiO2 (LMAS) glass-ceramics was synthesized by conventional method. The microstructure of LMAS GCs heat-treated at 760 °C/12 h + 930 °C/4 h was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spectroscopic properties of Co2+-doped LMAS GCs were studied by absorption spectrum, excitation spectrum, and temperature dependent luminescence spectra. XRD results revealed the sizes of MgAl2O4 crystalline phases are about 9.1 ± 1.5 nm. The three peaks in the visible absorption band of LMAS GCs at 549 nm, 585 nm and 626 nm are connected with the transitions from 4A2 level to 2A1/2T2(2G), 4T1(4P) and 2E/2T1(2G) levels, respectively, and excitations into them emit the radiation at around 666 nm. The luminescence intensity increased with temperature increasing from 10 K to 150 K, while it weakened with temperature increasing from 150 K to 350 K. These features were explained by the effects of two competing mechanisms.