Hopping conduction in calcium vanadate semiconducting glasses

The temperature and compositional dependences of the electrical conductivity of semiconducting calcium vanadate glasses have been reported in the temperature range 80-500 K. It has been observed that the multiphonon assisted hopping model of small polarons in the nonadiabatic regime, which considers the strong interaction of electrons with both the optical and acoustical phonons, can interpret the temperature dependence of the conductivity data of these glasses over the entire temperature range of measurement. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with the glass composition. On the other hand, Mott's nearest neighbour hopping model at high temperatures yields smaller values of the localization length. Moreover, Mott's variable range hopping model is consistent with the low temperature data