Thermoelectric properties of Sb doped AlFe$_2$B$_2$

Abstract: In this work, thermoelectric properties of Al${1.2}$Fe$_2$B$_2$ compound were investigated over a temperature range from 300\,K to 773\,K. Al${1.2}$Fe$2$B$_2$ compound was produced by vacuum arc melting of Al, Fe, and B followed by annealing at 1323 K under argon atmosphere. The annealed ingots were subsequently crushed into powder and hot pressed at 1273 K under vacuum. The hot-pressed alloy predominantly contained Al${1.2}$Fe$2$B$_2$ phase with a small fraction of FeB, which decreases further upon 0.1 \% Sb doping in Al${1.2}$Fe$2$B$_2$. The pristine Al${1.2}$Fe$2$B$_2$ exhibits n-type conductivity with a maximum figure of merit (zT) of 0.03 at 773\,K. The Sb doping improves the Seebeck coefficient at high temperatures and also reduces the phonon thermal conductivity across the temperature range studied. The decrease in phonon thermal conductivity is attributed to the point-defect phonon scattering due to mass fluctuation between the Fe and Sb atoms. The 0.1 at\% Sb doping at the Fe site results in improved zT of 0.056 at 773\,K in spite of its limited dissolution in Al${1.2}$Fe$_2$B$_2$ and forms FeSb$_2$ secondary phase.