ESR and ligand field theory studies of Nd2O3 doped borochoromate glasses

Glassy system of compositions xCr2O3–(25−x)Li2O–yNd2O3–(75−y)B2O3 where x = 0, 0.1, 0.2, 0.3, 0.5 at y = 1.0 mol% and x = 1.0, at y = 0 mol% has been prepared by conventional melt quenching technique. The electron spin resonance (ESR) of the prepared glassy system was investigated; the obtained ESR parameters indicate the presence of chromium ions predominantly in Cr3+ with small traces of Cr6+. The former is suggested to occupy modifier positions at lower Cr2O3 content (up to x = 0.3, y = 1 mol%). For higher Cr2O3 content (x > 0.3, y = 1 mol%) the chromium ions participate in the network as a former. The optical results have been analyzed in the light of ligand field theory. The value of the crystal field strength (Dq) and the inter-electronic repulsion Racah parameter (B) has been calculated from the optical transitions energies for all chromium doped glassy. The (Dq/B) ratio is found to be around 2.06; which indicate that the Cr3+ ions are in the weak ligand field sites. The IR absorption and density has been measured, the obtained data reveal that, both N4 ratio and density are almost composition independent.

► The xCr2O3–(25−x)Li2O–yNd2O3–(75−y)B2O3 glassy system was fabricated by a quenching method.
► ESR, IR and optical properties were studied and the ligand field theory was discussed.
► The conversion of chromium ions from Cr3+ to Cr6+ structural units occur at ∼x = 0.3 mol% of this study.
► The addition of Nd2O3 reduces the number of chromium ions Cr6+ ions.