Field effect studies on vanadium phosphate glasses

Field effect studies are made on vanadium phosphate glasses, containing a controlled amount of V4+ ions. These results do not support a pure 'hopping' conduction in these glasses. On the other hand, a trap controlled mobile carrier conduction in the extended states is indicated. Earlier experimental results suggestive of conduction via localised states, may possibly be reconciled by postulating the coexistence of 'band' and 'hopping' regions. Electrical conductivity, thermo-e.m.f. and optical absorption data are also presented. (author)