ELECTRICAL-CONDUCTIVITY OF ALPHA-HXV2O5 (X=0.00-0.27) - DEPENDENCE OFHYDROGEN CONCENTRATION AND ORIENTATION

The dependence of the electrical conductivity, sigma, on the hydrogen concentration and crystallographic orientation has been investigated u sing single crystals of HxV2O5, which were grown by the Bridgeman meth od and doped with hydrogen within the solid solubility in the alpha ph ase by the spillover technique. The temperature dependence of a showed the feature of diffusive hopping of thermally activated electrons abo ve similar to 180 K and variable range hopping below similar to 180 K. The dependence of sigma on the crystallographic orientation was littl e different from that of V2O5. The change in sigma with the hydrogen c oncentration was not monotonic; sigma increases with x up to x similar or equal to 0.06, but decreases above x similar or equal to 0.06. Thi s behaviour can be explained based on the competition between the incr ease in the carrier density and the depression of the mobility of carr iers with increasing x.