Thermoelectric properties of tetragonal HfH2 under doping effect: First principles study

Abstract

The effect of doping on the transport properties of HfH2 is explored using first-principles method and semi-classical Boltzmann approach. Thermoelectric properties such as electrical conductivity, Seebeck coefficient, electron and lattice thermal conductivity of doped and pure samples are calculated under various temperatures. The calculated results show that electrical and thermal conductivities increased with electron carrier concentrations similar to results reported by other studies in the low doping regime. While in the hole carrier concentration regime, irregular behavior is observed, especially in density of carriers equal to n = 4.6 × 1023 cm−3. Also, the lattice thermal conductivity and absolute value of Seebeck coefficient have been decreased with electron carrier concentration but these properties have irregular trend in the hole doping regime. Our results suggest that for achieving lower electron thermal conductivity with respect to pure HfH2, hole doping is much effective. Furthermore, the dispersive and large contribution of 5d orbital of Hf near the Fermi state and very low variation of L (Wiedemann-Franz factor) compared to the value of the free electron model L0, for pure and doped samples indicate that electrons in HfH2 have itinerant behavior and free-electron model is suitable to describe the transport properties of pure and doped samples of HfH2.