Intrinsic luminescence of the undoped glasses of (CaO-Ga2O3-GeO2) system

For the first time the intrinsic luminescence in the undoped (CaO-Ga2O3-GeO2) glasses with different composition has been found and investigated in the 80 divided by 300 K temperature range. The new glasses of high chemical purity and optical quality with stoichiometric composition similar to that in calcium-gallium-germanium garnet (Ca3Ga2Ge3O12), trigonal Ca-gallogermanate (Ca3Ga2Ge4O14), and Ca3Ga2O6 crystals were obtained by the high-temperature synthesis method. The luminescence and photoexcitation spectra analysis, supported by EPR spectroscopy data, yields the following results: (i) the UV-excited non-elementary broad emission band with maxima at roughly 500 nm and 420 nm in the (CaO-Ga2O3-GeO2) glasses is due to recombination of ensemble of the transient hole O- centres; (ii) the emission bands with maxima at nearly 380 and 710 nm, which were distinctly revealed in glasses with the Ca3Ga2Ge4O14 and Ca3Ga2O6 compositions, are assigned to the luminescence of UV-induced electron centres of two different types. Possible models of the luminescence centres in (CaO-Ga2O3-GeO2) glass network are discussed.