Role of sintering temperature on electronic and mechanical properties of thermoelectric material: A theoretical and experimental study of TiCoSb half-Heusler alloy

Abstract

Ternary half-Heusler (HH) alloys are being widely explored for mid temperature range thermoelectric (TE) applications. Here, we have discussed the effect of sintering temperature on electronic, structural and mechanical properties of TiCoSb HH alloy. Four samples of TiCoSb were synthesized employing arc melting followed by spark plasma sintering at different sintering temperatures. Subsequently, the phase purity of all the synthesized samples was confirmed by X-ray diffraction (XRD) analysis. The crystallite size is calculated employing Williamson-Hall method, which increases monotonically with sintering temperature. The morphology coupled with compositional analysis of the samples was studied employing Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDS), respectively. Further, these samples were characterized for their electronic transport properties. The overall transport properties which are represented by power factor (PF) found to be increasing with sintering temperature. A maximum value of power factor ∼0.79 mW/m-K2 at ~625 K is achieved for sample sintered at 1423 K. Furthermore, the mechanical properties (micro-hardness and fracture toughness) were found to be increased monotonically with increasing sintering temperature. To understand the underlying physics, the electronic structure and transport properties of the material have been studied by using first principles-based Density Functional Theory (DFT).