Spectroscopic characterization, conductivity and relaxation anomalies in the Li2O–MgO–B2O3 glass system: Effect of nickel ions

Glass samples of the system, Li2O–MgO–B2O3 containing different concentrations of nickel oxide (ranging from 0 to 1.0 mol%) were prepared by using the melt quenching technique. The optical absorption studies indicate that the nickel ions occupy both tetrahedral and octahedral positions in the glass network. However, the octahedral positions seem to be dominant when the concentration of nickel oxide is ⩽0.4 mol% in the glass matrix. When in the octahedral positions, nickel ions occupy the network modifying positions. This has a tremendous effect on the thermoluminescence, electrical conductivity and magnetic susceptibility studies. Electrical measurements were carried out as a function of frequency and temperature over the frequency range of 10–106 Hz and a temperature range of 303–523 K. The electric modulus formalism was applied to study the relaxation behavior by using the impedance data for all the samples at 403 K, and also for analyzing the relaxation behavior of the highest conducting sample (0.4 mol% of nickel oxide) at different temperatures. An attempt has been made to relate the measured properties to the structural modifications in the glass network due to the modifying effect of octahedral Ni2+ ions.