Enhancement of the power factor of the transition metal pentatelluride HfTe5 by rare-earth doping

The transition metal pentatellurides HfTe5 and ZrTe5 have been observed to possess interesting electrical transport properties with high thermopower and low resistivity values leading to high thermoelectric power factors. We have investigated the effect of doping HfTe5 with rare-earth elements by measuring the power factor data from about 10K to room temperature on single crystals of Hf1−xRxTe5, where R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, and Ho. Samples that have been doped with Nd (Hf1−xNdxTe5) possess power factors more than a factor of 2 larger than that of the commonly used thermoelectric material Bi2Te3.