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)R 2 B 4 O 7 - x PbO- y CuO-(15- x /2- y )TeO 2 ( x = 0,10; y = 0.1-1.5; R = Li, Na or K) glasses were studied. EPR spectra of all the glasses show resonance peaks characteristic of Cu 2+ 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 paramagnetic susceptibility was calculated from the EPR data at various temperatures and the Curie constant was calculated from the 1/ - T graph. The optical absorption spectra of all the samples show a broad absorption band; the position 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 E were calculated for all the glass samples from their ultraviolet edges. The optical energy gap varies between 3.4 and 2.7 eV and increases from Li to K glasses. Also, it was observed that as copper ion concentration is increased, E opt decreases while E increases. This was explained as due to change in non-bridging oxygen content. Raman spectra of three samples were recorded at room temperature. The bands were assigned as due to various groups of boron.