EPR and optical absorption of Cr3+ ions in ternary K2SO4-Na2SO4-ZnSO4 glasses

Electron paramagnetic resonance (EPR) spectrum of Cr3+ ions doped ternary K 2SO4Na2SO4-ZnSO4 glasses has been studied at different temperatures. The lo w field spectral resonance lines of the EPR spectra of Cr3+ ions in K2SO4-N a2SO4-ZnSO4 glasses are attributed to isolated Cr3+ ions whereas the high f ield spectral resonance line is attributed to exchange-coupled pairs of Cr3 + ions. The optical absorption spectrum of Cr3+ ions doped glass shows two broad bands characteristic of Cr3+ ions in octahedral symmetry. From the op tical spectrum, the crystal field parameter (Dq) and the Racah interelectro nic repulsion parameters (B and C) have been evaluated. From the EPR and op tical spectral data, it is concluded that the site symmetry around Cr3+ ion s is octahedral and the nature of bonding is predominantly covalent in natu re.