Origin and properties of the nearly constant loss in crystalline and glassy ionic conductors

We report on the temperature and mass dependence of the nearly constant loss (NCL) in several ionically conducting materials, both crystalline (Li-0.18 La-0.61 TiO3 and (Y2O3)(0.16) (ZrO2)(0.84)) and glassy (M2O . 3B(2)O(3), M = Li, Na, K and Rb). The magnitude A of the NCL is found to be larger for those materials showing higher dc conductivity values at room temperature, and shows weak temperature dependence of the form A proportional to exp(bT) in all cases. We have also found that A systematically decreases upon increasing the mass of the mobile alkali ion in the borate glasses. All these results point to the relaxation of ions in a very slowly decaying cage as the origin of the NCL. (C) 2002 Elsevier Science B.V. All rights reserved.