Further evidence for a ‘‘second universality’’ in alternating-current conductivity relaxation

Abstract

The existence of a regime of constant-loss (independent of frequency) behavior was reported earlier, based on ac conductivity measurements at low temperatures and/or high frequencies, for a wide range of ionically conducting crystalline materials and glasses. Here new results in support of this concept are presented. First, it is shown that the example of NaCl:Zn2+ which Macdonald examined in detail [J. Appl. Phys. 75, 1059 (1994)] is a poor one to serve as a test of constant-loss behavior. Additional cryogenic measurements, and a more detailed analysis of both the real and imaginary parts of the complex dielectric constant for materials such as crystalline CaTiO3:Al3+ and Na2O⋅3SiO2 glass are shown to support the conclusion that constant-loss behavior occurs at low temperatures for a wide range of materials.