Radiation-Induced Paramagnetic Centers in the Glasses Of CaO-Ga2O3-GeO2 System

Abstract

The X-band (v ≅ 9.4 GHz) ESR spectra of the UV-, X-, and γ-irradiated glasses of CaO-Ga2O3-GeO2 system with compositions similar to Ca3Ga2Ge3O12, Ca3Ga2Ge4O14, and Ca3Ga2O6 crystals have been investigated at 300 and 77 K. It was shown that X- and γ-irradiation of the Ge-contained glasses induce simultaneously electron and hole paramagnetic centers, stable at room temperature. The UV-irradiation of Ge-contained glasses leads to the generation of stable centers of electron type, whereas the X- and γ-irradiation of glasses with Ca3Ga2O6 composition induces stable hole centers, exclusively. The electron centers are assigned to E′ (Ge) centers with different local environments. ESR spectrum of hole centers is ascribed to O− centers, localized on non-bridging oxygen of the glass network. The E′ (Ge) and O− centers show high thermal stability in the CaO-Ga2O3-GeO2 glass network. The obtained ESR spectra are described by spin Hamiltonian with g-factor of axial and rhombic symmetry for the E′ (Ge) and O− centers, respectively. The nature, electron structure and some formation peculiarities of the radiation defects in CaO-Ga2O3-GeO2 glasses are discussed in comparison with other glasses as well as Ca3Ga2Ge3O12 and Ca3Ga2Ge4O14 crystals.