Dielectric and conductivity studies on lead silicate glasses having mixed alkali and alkaline earth metal oxides

摘要

Lead silicate glasses containing different amounts of Na2O and K2O along with BaO were prepared by conventional melt and quench method. Dielectric constant and its dispersion were investigated as a function of frequency over the range 10 kHz to 5 MHz at room temperature. Ionic conductivity was studied on three selected mixed alkali glasses (Na2O)(0.069) - (K2O)(0.036) - (BaO)(0.026) - (PbO)(0.11) - (SiO2)(0.76) (LS31), (Na2O)(0.066) - (K2O)(0.07) - (BaO)(0.021) - (PbO)(0.106) - (SiO2)(0.736) (LS1) and (Na2O)(0.062) - (K2O)(0.013) - (BaO)(0.02) - (PbO)(0.099) - (SiO2)(0.689) (LS33) as a function of frequency over the range 100 Hz to 500 kHz in the temperature interval 25-380degreesC in vacuum of 10(-2) mbar. Both DC conductivity and the hopping frequency, inferred from the analysis of AC conductivity data, exhibit Arrhenius behaviour with temperature. Unlike the conventional mixed alkali system, in the present glass system, it is found that the activation energies associated with DC conduction (E-sigma) and that of hopping process (E-h) for LS1, having nearly equal amounts of Na+ and K+ ions, are found to be less compared to those for glasses LS31 and LS33. E-sigma (1.14 eV) calculated for LS1 using Anderson-Stuart model agrees well with that obtained experimentally (1.18 eV). The above behaviour observed in E-sigma and E-h for the present glass system may be attributed to the complex effect due to both mixed alkali effect and the structural changes introduced by the change in SiO2 content.