Pressure dependence of the large-polaron transport in anatase TiO2 single crystals

We have measured the pressure and temperature dependences of the resistivity and the thermoelectric power of anatase, TiO2. The resistivity varies with T-3 at high temperatures, and its absolute value is in the 1 Omega cm range. Below 60 K, the resistivity is activated. Most surprisingly, the activation energy shows non-monotonic pressure dependence. The thermoelectric power has a very high value and its temperature dependence resembles that of polaronic materials. We suggest a large polaronic model to describe the temperature and pressure dependence of the two transport coefficients. Copyright (c) EPLA, 2012