Ac and dc conductivities in V2O5–P2O5 glasses containing alkaline ions

We investigated the ac and dc conductivity in 50V2O5–(50 − x)P2O5–xA2O (A = Li, Na, K) glasses as a function of temperature. The measurements were carried out in the frequency range from 10−4 to 107 Hz. For all compositions, the dc conductivity decreased with the increasing alkali ion content. The decrease in conductivity was more pronounced for larger alkali ions. The ac conductivity exhibited a universal dynamic response: σac = Aωs(T). For glasses containing less than 10 mol% of alkaline ions, the exponent s(T) temperature dependence was typical as that for electronic conducting glasses and decreased from a value near to unity at a low temperature (153 K) to 0.5 at 423 K. A small variation only (from 0.99 to 0.95) of s(T) was observed in the mixed electronic–ionic regime. This behavior is known as nearly constant loss (NCL). We found that the NCL behavior could be observed in a very wide range of temperature and frequency in mixed electronic–ionic conducting glasses.