The nature of intrinsic luminescence in glasses and crystals of CaO-Ga2O3-GeO2 system

Intrinsic luminescence of undoped glasses and crystals of CaO-Ga2O3-GeO2 system with different compositions is investigated. Using synchrotron excitation, the emission and time-resolved luminescence excitation spectra, as well as the luminescence kinetics are studied at T = 8 K for the undoped glasses and crystals with garnet Ca3Ga2Ge3O12 composition and the glasses with Ca3Ga2O6 composition. The observed luminescence spectra strongly depend on the basic glass composition and the excitation energy. They consist of several (up to four) broad emission bands located in the visible spectral range. Basing on comparative analysis of the emission and excitation spectra and the decay kinetics in the glasses and crystals of CaO-Ga2O3-GeO2 system, we propose recombination mechanism of the intrinsic luminescence. Specific models suggested for the intrinsic luminescence are supported by electron spin resonance spectroscopic results