ESR AND OPTICAL-ABSORPTION SPECTRA OF NI(II) IONS IN LITHIUM FLUOROBORATE GLASSES

The results of the investigation of the structure of Ni(ll) ions in x LiF-(100 - x) B2O3 glasses with 5 less than or equal to x less than or equal to 30 mol% using ESR and optical absorption techniques are repo rted. Electron spin resonance spectra of Ni(ll) ions doped glasses exh ibit a symmetric line shape centred at g=2.36+/-0.01 at room temperatu re. Remarkable changes have been observed in the intensity and line sh ape with changes in concentration of LiF and when the spectra were rec orded in the temperature range 123-453 K. The optical absorption spect ra were recorded at room temperature. The observed bands have been int erpreted in terms of ligand field theory. From the spectral analysis, the crystal field parameter, Dq, and the Racah interelectronic repulsi on parameters, B and C, have been evaluated. By correlating the ESR an d optical absorption data, the covalency parameter has been evaluated.