Thermoelectric properties of Fe$_{2}$VAl at high temperature region: A combined experimental and theoretical study

TL;DR

This study combines experimental measurements and electronic structure calculations to analyze the thermoelectric properties of Fe₂VAl from 300 to 800 K, revealing its n-type behavior and the influence of multi-band electronic contributions.

Contribution

The paper provides a comprehensive combined experimental and theoretical analysis of Fe₂VAl's thermoelectric properties at high temperatures, highlighting the role of multi-band effects.

Findings

Fe₂VAl exhibits n-type thermoelectric behavior with a Seebeck coefficient decreasing from -138 to -18 μV/K.

Electrical conductivity increases while thermal conductivity decreases with temperature.

DFT calculations successfully explain the experimental thermoelectric properties in the 300-800 K range.

Abstract

Heusler type compounds have long been recognized as potential thermoelectric (TE) materials. Here, the experimentally observed TE properties of Fe$_{2}$VAl are understood through electronic structure calculations in the temperature range of $300-800$ K. The observed value of $S$ is $\sim-$138 $\mu$V/K at 300 K. Then, the $|S|$ decreases with increase in temperature up to the highest temperature with the value of $\sim-$18 $\mu$V/K at 800 K. The negative sign of $S$ in the full temperature window signifies the dominating $n$-type character of the compound. The temperature dependent of electrical conductivity, $\sigma$ (thermal conductivity, $\kappa$) exhibits the increasing (decreasing) trend with the values of $\sim$1.2 $\times$ 10$^{5}$ $\Omega^{-1}$m$^{-1}$ ($\sim$23.7 W/m-K) and $\sim$2.2 $\times$ 10$^{5}$ $\Omega^{-1}$m$^{-1}$ ($\sim$15.3 W/m-K) at 300 K and 800 K, respectively. In order to understand these transport properties, the DFT based semi-classical Boltzmann theory is used. The contributions of multi-band electron and hole pockets are found to be mainly responsible for the temperature dependent trend of these properties. The decrement of $|S|$ and increment of $\sigma/\tau$ $\&$ $\kappa_{e}/\tau$ ($\tau$ is relaxation time) with temperature is directly related with the contribution of multiple hole pockets. Present study suggests that DFT based electronic calculations provide reasonably good explanations of experimental TE properties of Fe$_{2}$VAl in the high temperature range of $300-800$ K.