ELECTRICAL-CONDUCTION AND DIELECTRIC-RELAXATION IN VANADIUM PHOSPHATE-GLASSES

Electrical conduction and dielectric relaxation in (V2O5)(1-x)(P2O5)(x ) glasses (where x = 0.12, 0.18 and 0.24) have been investigated in th e temperature range 300-560 K and frequency range 50 Hz-10 kHz. The te mperature dependences of both bull; and d.c. conductivities are descri bed by the Mott and Davis equation for conduction in amorphous solids with activation energies of 0.0355-0.0546 eV and 0.4-0.47 eV, respecti vely. The results of d.c. conductivity are discussed on the basis of s mall polaron hopping between V4+ and V5+ sites beyond theta(D)/2, wher eas the results of bulk conductivity are discussed according to the el ectron hopping between filled and empty localized states at the Fermi level. The a.c. conductivity is found to obey the power relation sigma =A omega(n). Reasonable values of both hopping rate and relaxation tim e are obtained and discussed. The results of conduction as well as die lectric properties are discussed on the basis of both bulk and domain interfaces, which play a significant role in both conduction and relax ation processes in the glass matrix. (C) 1998 Elsevier Science S.A. Al l rights reserved.