ELECTRON-PARAMAGNETIC-RESONANCE AND OPTICAL-ABSORPTION STUDIES OF FE(III) IONS IN ALKALI BARIUM BORATE GLASSES

Electron paramagnetic resonance (EPR) and optical absorption studies o f Fe(III) ions doped in 20 M2O + (25 -x) BaO + 55B(2)O(3) + xFe(2)O(3) (M = Li, Na or K, 0.25 less than or equal to x less than or equal to 10) glasses were carried out. The EPR spectra have resonances at g = 1 0 +/- 0.5, g = 6.4 + 0.1, g = 4.2 +/- 0.1 and g = 2.0 +/- 0.1. The EPR spectra of x = 0.5 mol% of Fe2O3 in sodium barium berate glass sample was studied at various temperatures. The linewidths were found to be unaffected by temperature changes, while the intensity increases with decrease in temperature. From the concentration dependence of the g = 4.2 and g = 2.0 resonances in sodium-barium berate glasses it was obse rved that clusters of iron are formed for Fe2O3 contents > 3 mol%. The optical absorption spectrum of Fe(III) ions in such a glass exhibits six bands characteristic of Fe(III) ions in octahedral symmetry. From the analysis of the bands, the crystal-field parameter, and the Racah interelectronic repulsion parameters B and C were estimated. (C) 1998 Elsevier Science B.V.