Low temperature resistivity, thermoelectricity, and power factor of Nb doped anatase TiO2

The resistivity of a very high quality anatase TiO2 doped with 6% of Nb was measured from 300K down to 40 mK. No sign of superconductivity was detected. Instead, a minute quantity of cation vacancies resulted in a Kondo scattering. Measurements of thermo-electric power and resistivity were extended up to 600 K. The calculated power factor has a peak value of 14 mu W/(K(2)cm) at 350 K, which is comparable to that of Bi2Te3 [Venkatasubramanian et al., Nature 413, 597 (2001)], the archetype thermolectrics. Taking the literature value for the thermal conductivity of Nb doped TiO2 thin films, the calculated figure of merit (ZT) is in the range of 0.1 above 300 K. This value is encouraging for further engineering of the material in order to reach ZT of 1 suitable for high temperature thermoelectrics. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773517]