Spectroscopic investigations on Cu(II) ions doped in alkali lead borotellurite glasses

Electron paramagnetic resonance, optical absorption spectra, Raman spectra and physical properties of copper(II) ions in (85 - x/2)R2B4O7-xPbO-yCuO-(1 5 - x/2 - y)TeO2 (x = 0,10; y = 0.1-1.5; R = Li, Na or K) glasses were stud ied. EPR spectra of all the glasses show resonance peaks characteristic of Cu2+ ions. The number of spins participating in the resonance was measured as a function of temperature and the activation energy was calculated. From the EPR and density measurements, the ratio of number of copper ions in +2 state to the total copper ions (i.e., N-2/N-T) was calculated. The paramag netic susceptibility was calculated from the EPR data at various temperatur es and the Curie constant was calculated from the 1/chi-T graph. The optica l absorption spectra of all the samples show a broad absorption band; the p osition of the band maxima varies from 14 500 to 12 700 cm(-1) for glasses with different alkali ions. The optical energy gap E-opt and Urbach energy Delta E were calculated for all the glass samples from their ultraviolet ed ges. The optical energy gap varies between 3.4 and 2.7 eV and increases fro m Li to K glasses. Also, it was observed that as copper ion concentration i s increased, E-opt decreases while Delta E increases. This was explained as due to change in non-bridging oxygen content. Raman spectra of three sampl es were recorded at room temperature. The bands were assigned as due to var ious groups of boron.