| Sumario: | The thermoelectric power and the resistivity of V2O5- TiO2 mixtures over ranges of composition and temperature from 20° to 500° in air have been measured, The mixtures were obtained by coprecipitation of aqueous solutions of NH4VO3 and TiCl4. calcined during 90 h at 550° and then sintered. Resistances were measured by the four points method. At the VO5/2 35–100% M range, the activation energies for conductivity change from 0,36 to 0.62eV, while for the thermoelectric power they change from 0,18 to 0.24eV. It can be assumed from these values that the conduction mechanism over this concentration range is due to the “hopping” of small polarons, arising principally, from the presence of V4+ ions. In the samples with a high TiO2 content, the activation energies for conductivity were 0.82 and 0.36eV, for the different samples. From the variation of thermoelectric power with temperature, it can be assumed that the ionization energy of the donors centers lies at 0.83eV under the conducting band. A mechanism for band conduction is inferred from the results, being the V4+ donating centers and the V5+ receptive centers.
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