EPR STUDY OF THE IMPURITY PARAMAGNETIC CENTERS IN (CAO-GA2O3-GEO2) GLASSES

The X-band EPR spectra of Cr3+, Mn2+, and Fe3+ impurity ions in glasse s of (CaO-Ga2O3-GeO2) system are investigated in the 77 divided by 300 K temperature range. The experimental data analysis yields the follow ing results: (i) Impurity chromium ions are incorporated into the (CaO -Ga2O3-GeO2) glasses network in Cr3+ (3d(3), F-4(3/2)) paramagnetic va lence state only and occupy the strong distorted oxygen coordinated oc tahedral sites. (ii) For all activated and non-activated (CaO-Ga2O3-Ge O2) glasses the iron impurity is present at concentration roughly 0.01 wt%. Isotropic EPR signals at g(eff) = 4.29 and g(eff) = 2.00 are ass igned to Fe3+ (3d(5), S-6(5/2)) ions in the sites with strong rhombic distortion and in the sites with nearly cubic symmetry respectively. ( iii) The manganese EPR spectrum in (CaO-Ga2O2-GeO2) glasses is weakly dependent on temperature, doping procedure as well as manganese concen tration. EPR spectra of impurity manganese ions in glasses with Ca3Ga2 Ge3O12 and Ca3Ga2Ge4O14 compositions are virtually identical and belon g to Mn2+ (3d(5), S-6(5/2)) ions. Impurity manganese ions are incorpor ated into the (CaO-Ga2O3-GeO2) glass network as isolated Mn2+ centres and clusters of Mn2+ ions.