Significance of intermediate range structure for electrical conduction in alkali germanate glasses

The dc ionic conductivity of the xM(2)O:(1-x)GeO2 glass series has been measured as a function of temperature and composition where M is K or Rb and 0.0023 less than or equal to x less than or equal to 0.60. The structure of the same glasses have been determined by measuring X-ray absorption fine structures, densities and X-ray photoelectron, Raman and infrared absorption spectroscopies. With increasing alkali concentration the activation energy of conductivity decreases followed by an increase and then a more rapid decrease at x approximate to 0.1. By correlating this complex composition dependence of electrical conductivity with the structural information we demonstrate that the intermediate range structure of glass affects ion transport in alkali germanate glasses. (C) 1997 Elsevier Science B.V.