Dielectric dispersion in molybdenum phosphate glasses

Dielectric measurements for an 85 mol.% MoO3-15 mol.% P2O5 glass sample have been made from 77K to 475K at four fixed frequencies 0.1 kHz, 1 kHz, 10 kHz and 100 kHz. It has been observed that a Debye-type dielectric relaxation exists in the temperature region where AC conductivity at a given frequency approaches DC conductivity. A distribution of relaxation times is needed to explain the relaxation behaviour; however, the value of the distribution parameters is much smaller than that required to account for the almost linear dependence of conductivity on frequency. A comparison with vanadate glasses shows that the numerical magnitude of the Cole-Cole distribution parameter is almost the same for both the systems.