Thermoelectric Performance Boost by Chemical Order in Epitaxial L2$_1$ (100) and (110) Oriented undoped Fe$_2$VAl Thin Films: An Experimental and Theoretical Study

Abstract

This study demonstrates the direct correlation between the presence of the L2$_1$ ordered phase and the large enhancement in the thermoelectric performance of Fe$_2$VAl thin films deposited on MgO and Al$_2$O$_3$ substrates at temperatures varying between room temperature and 950$^{\circ}$C. We employ both experimental techniques and computational modeling to analyze the influence of crystallographic orientation and deposition temperature on the thermoelectric properties, including the Seebeck coefficient, electrical conductivity, and thermal conductivity. Our findings indicate that the presence of the L2$_1$ phase significantly enhances the power factor (PF) and figure of merit (zT), surpassing previously reported values for both bulk and thin film forms of Fe$_2$VAl, achieving a PF of 480 $\mu$W/m$\cdot$K$^2$ and a zT of 0.025.