Polarization and Conduction Mechanism in Mixed-Alkali Glasses

Thermally stimulated polarization and depolarization current (TSPC/TSDC) measurements on mixed alkali (Li-Na) silicate glasses show two TSDC peaks along with a dc conduction current at high temperatures, similar to single-alkali silicate glasses. The activation energies for the two TSDC peaks and for dc conduction increase with the addition of a second alkali. The first TSDC peak does not change in size but the second becomes substantially smaller when the second alkali is added. The reduction in size of the second TSDC peak correlates well with the reduction in the dielectric loss hi mixed-alkali glasses. A model is proposed to account for the behavior of the two TSDC peaks.