High Thermoelectric Figure of Merit of FeSb2−x Thin Films via Defect Engineering for Low-Temperature Cooling Applications

Abstract

In general, both the thermal and electrical conductivity of metal/metalloid/semimetal materials decrease with increasing temperature; that is, these two parameters are in lockstep. Defect engineering has recently been proven to have tremendous potential for improving the thermoelectric performance of topological materials with two-dimensional layered structures. We have explored the effect of Sb point-defect engineering on the thermoelectric performance of FeSb 2−x (x = 0, 0.1, 0.2, and 0.3) thin films at low temperatures. Thin-film surface and grain-boundary phonon scattering contribute to the overall decrease in the thermal conductivity (κ) compared with single crystals. The current results indicate that FeSb 1.8 shows the lowest κ value, the main reason being that its nanostructure scatters more phonons over a wider wavelength range. In addition, the presence of Sb point defects enables an enhancement of the Seebeck coefficient (S) to 357 μV/K at 45 K for FeSb 1.8 thin films, coupled with an imperceptible decrease in the corresponding electrical conductivity (σ). Despite these results, the power factor (PF) is much lower than that of single crystals. The optimal peak thermoelectric figure of merit (ZT) of ~ 0.071 at 55 K is one order of magnitude higher than the ZT max of low-temperature FeSb 2 single crystals. These characteristics indicate that FeSb 2 thin films are promising materials for use in low-temperature thermoelectric devices.

Bottom-up fabrication of FeSb2 nanowires on crystalline GaAs substrates with ion-induced pre-patterning

“…However, FeSb 2 nanowires with a Sb deficiency could be favorable for thermoelectric applications. Sanchela et al [42] and Li et al [43] reported the improvement of the thermoelectric properties for polycrystalline FeSb 2 with a Sb deficiency. This is based on the reduction of the phononic thermal conductivity as well as the increase of the Seebeck coefficient.…”

“…This is based on the reduction of the phononic thermal conductivity as well as the increase of the Seebeck coefficient. Additionally, Li et al [43] described a two orders of magnitude higher electrical conductivity for thin films of FeSb 2-x (x = 0, 0.1, 0.2, 0.3). In view of these results, it would be interesting to advance our approach for nanostructuring FeSb 2 with an improved control of the deposited Fe:Sb ratio.…”