Electronic conductivity and thermopower of Ca2NaMg2V3O12−x garnet

Results are reported from conductivity and thermoelectric power measurements on partially reduced Ca₂NaMg₂V₃O_12?x, with x < 5.10^?2, at temperatures of 300–1100 K. The conductivity is thermally activated with activation energies 0.26 ? E_a ? 1.28 eV for differently reduced samples. The thermopower is temperature independent in the 300–800 K region. These results are shown to be consistent with the adiabatic hopping of small polarons localised on the vanadium sublattice, where defect interactions result in the formation of multiple conduction pathways.