Physical properties of the poly-vanadium-molybdenum acid xerogels

Abstract

Measurements of charge transport in thin layers of poly-vanadium-molybdenum acid, described by the general formula H 2V 12− x Mo x O 31± y · nH 2O where x=0, 0.5, 1, 2 and 3, are presented. From the results of three experiments (conductance and capacitance frequency dependencies, Cole–Cole diagrams, and transient current measurements) on charge transport in H 2V 12− x Mo x O 31± y · nH 2O thin films, the mobilities of the carriers along ( μ ‖) and across ( μ ⊥) V–O–Mo layers were determined: μ ‖≈10 −8 m 2/V s, μ ⊥≈10 −12 m 2/V s. The carrier concentration is n≈10 25 m −3. The anisotropy of the conductivity of poly-vanadium-molybdenum acid is caused by the mobility anisotropy. The frequency dependencies of the conductance and capacitance of the xerogels were described by a model which took into account the interaction between the drift charge and its environment. The conductance and capacitance of the investigated compounds depends on the relative humidity of the surrounding atmosphere when the amount of molybdenum in the materials is not equal to zero.