Protonic and photoconductivity studies on heteropolyanion of H3+xPVxW12-xO40 center dot n H2O single crystals

Protonic conductivity measurements are reported for H3+xPVxW12-xO40 . nH(2) O single crystals with x = 1, 2 and 3. The analysis of log sigma versus 10( 3)/T curves suggests that the conductivity increases with increase in tempe rature in the crystals with two distinct linear regions. The activation ene rgy in the first region decreases with increase in vanadium concentration. There is a general trend towards increase in room temperature conductivity with increase in vanadium concentration. Steady stale photoconductivity mea surements have been studied at different illumination levels and the ln I-p h, versus in F plots indicate the existence of a continuous distribution of localised states in these materials. The photosensitivity increases with i ncrease in x. The photo decay time constant is found to be a multivalued fu nction and the decay law is nearly hyperbolic.