Enhanced thermoelectric performance of p-type ZrCoSb0.9Sn0.1 via Tellurium doping

Abstract

Doping strategy has been shown as an effective paradigm in most of the thermoelectric materials for optimization of high ZT. Herein, we have synthesized several compositions of Te doped p-type ZrCoSb0.9-xSn0.1Tex (0≤ × ≤0.08) Half-Heusler (HH) alloys employing arc melting followed by spark plasma sintering (SPS). X-ray Diffraction (XRD) analysis reveals the formation of single phase of MgAgAs type HH phase. Thermoelectric properties were measured from room temperature to 773 K. Interestingly, Te doping on Sb site in ZrCoSb0.9-xSn0.1Tex leads to decrease of lattice thermal conductivity and a minimum lattice thermal conductivity~ 1.98 WK−1m−1 at 773 K for composition ZrCoSb0.9-xSn0.1Tex (x = 0.08) was optimized. The reduction in thermal conductivity is attributed to scattering of phonons by mass fluctuation and grain boundaries. In addition to this, significant improvement in power factor (~16.89 μWK−2cm−1at 773K) for ZrCoSb0.9-xSn0.1Tex (x = 0.06) was observed to be optimized. The enhancement in power factor is mainly attributed due to increased Seebeck coefficient manifested by reduction in effective hole carrier density occurred by Te substitution on Sb site. Thus, combination of reduced thermal conductivity and enhanced power factor obtained via Te substitution at Sb site leads to a high ZT~ 0.53 for ZrCoSb0.9-xSn0.1Tex (x = 0.06). The present ZT~ 0.53 optimized for ZrCoSb0.9-xSn0.1Tex (x = 0.06) is 150% larger than that of un-doped ZrCoSb0.9Sn0.1 compound.