Thermomagnetic Transport in Polycrystalline Samples

Polycrystalline/single-phase nanocomposite samples are used widely for thermoelectrics and many other applications. The presence of many interfaces improves the thermoelectric properties by suppressing phonon transport more than electron transport. When polycrystalline samples are made out of anisotropic crystals, it is not clear how the transport properties are related to those of single crystal. In this paper, we describe a simple process of averaging over different crystallographic directions to calculate the properties of isotropic polycrystalline samples made out of anisotropic crystals. We apply the developed averaging model to (Bi0.2Sb0.8)(2)Te-3 samples for which experimental data are available. We further point out the importance of thermomagnetic measurements in providing additional information on electron relaxation times, compared with what regular thermoelectric measurements reveal.