Electronic and phonon contributions to the Thermoelectric properties of newly discovered half-Heusler alloys XHfPb (X= Ni, Pd, and Pt)

Abstract

In this work we calculate the thermoelectric figure of merit of XHfPb (X= Ni, Pd, and Pt) by computing the both the power factor and the lattice thermal conductivity by first principles. We make reasonable approximations: we use the Constant Relaxation Time Approximation (CRTA) to compute the electron transport contribution and the modified Debye-Callaway model to calculate the thermal lattice conductivity. We also report the dielectric properties of these semiconductors and the mode Grüneisen parameters. Not surprisingly we find that the average Grüneisen coefficient correlates with the tehrmal conductivity. Next, we consider a realistic relaxation time $\tau$ and carrier concentration $n$ from experimental data on ZrHfPb and obtain the figure of merit $ZT$ as a function of temperature. Our main finding is that despite the Pt is isoelectronic with Ni and Pd, the $ZT$ of PtHfPb is larger and behaves differently from the other two materials, suggesting that PtHfPb is better suited for high temperature thermoelectric generators.

19 pages, 6 figures, 4 tables

References in corpus (7)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• BoltzTraP. A code for calculating band-structure dependent quantities
• Distribution of phonon lifetime in Brillouin zone
• Prediction and accelerated laboratory discovery of previously unknown 18-electron ABX compounds
• Thermal physics of the lead chalcogenides PbS, PbSe, and PbTe from first principles
• Lattice thermal conductivity of Ti${}_x$Zr${}_y$Hf${}_{1-x-y}$NiSn half-Heusler alloys calculated from first principles: Key role of nature of phonon modes
• Examining the thermal conductivity of half-Heusler alloy TiNiSn by first-principles calculations