EPR and FT-IR spectroscopic studies of B2O3Bi2O3MnO glasses

The effect of silicate network modifiers on colour and electron spectra of transition metal ions

Thermal, structural and magnetic properties of some zinc phosphate glasses doped with manganese ions

The structural influence of chromium ions in lead gallium phosphate glasses by means of spectroscopic studies

ZnO–Sb2O3–B2O3 glasses containing different concentrations of chromium ions (introduced as CrO2–4) ranging from 0 to 1.0 mol% were prepared. A number of studies viz., differential thermal analysis, infrared, optical absorption, Raman and ESR spectra and dielectric properties (constant e ′, loss tan δ, a.c. conductivity σac over a wide range of frequency and temperature) of these glasses have been carried out. The results have been analyzed in the light of different oxidation states of chromium ions. The analysis indicates that when the concentration of chromium ions is ∼0.2 mol%, these ions mostly exist in Cr6+ state, occupy network forming positions with CrO2–4 structural units and increase the rigidity of the glass network. When the concentration of the chromium ions is increased beyond 0.2 mol%, these ions seem to be reduced from Cr6+ state to Cr5+ and Cr3+ states. A gradual transformation of chromium ions from tetrahedral positions to octahedral positions could also be established from these results. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Valence and coordination of chromium ions in ZnO-Sb2O3-B2O3 glass system by means of spectroscopic and dielectric relaxation studies

By using X-ray diffraction analysis, EPR and magnetic measurements, the chromium-ion distribution in xCr2O3-(1−x) [3B2O3-PbO] glasses with 0⩽x⩽35 mol% Cr2O3 was studied. EPR investigation evidenced the presence of both Cr3+ and Cr5+ ions, the latter being in small proportion, in agreement with the atomic magnetic moment values. For concentrations x⩽20 mol% Cr2O3 the isolated Cr3+ ions coexist with those coupled by super-exchange magnetic interactions, the isolated ones prevailing only for x 20 mol % Cr2O3 microcrystalline precipitates were detected, giving rise to an antiferromagnetic transition with Neel temperature, NN≃310 K and paramagnetic Curie temperature, θp=−480 K.

Gh. Ilonca

Papers

EPR and magnetic susceptibility studies of xCr2O3-(1-x) 3B2O3-PbO glasses

EPR studies of Mn2+ ion distribution in xMnO·(100-x) [19TeO2·PbO] glasses