Anomalous Power Factor Enhancement and Local Structural Transition in Ni-Doped TiCoSb

TL;DR

This study demonstrates a significant power factor enhancement in Ni-doped TiCoSb due to a local structural transition at a specific doping level, combining experimental and theoretical insights.

Contribution

It reveals how minute Ni doping induces a local structural transition and enhances the power factor in TiCoSb, supported by first-principles calculations and advanced structural analysis.

Findings

269% increase in power factor at x=0.02

Local structural transition confirmed by XRD and XAS

Enhanced thermoelectric performance due to disorder-to-order transition

Abstract

We report a significant enhancement (~269%) in the power factor (PF) and a local structural transition in Ni-doped TiCoSb samples (TiCo_{1-x}Ni_xSb, (x= 0.0, 0.01, 0.02, 0.03, 0.04, and 0.06). First-principles calculations reveal that even minute Ni doping induces a substantial shift in the Fermi level (EF) and alters the density of states (DOS). Structural analysis via Rietveld refinement of X-ray diffraction (XRD) data shows anomalous behavior at x = 0.02, supported by Williamson-Hall and modified methods. X-ray absorption spectroscopy (XAS) at the Ti and Co K-edges further confirms a pronounced local structural change at this composition. These structural transitions are consistent with temperature-dependent resistivity (\rho(T)) and thermopower (S(T)) data, which reflect changes in EF and disorder. Analysis of Lorentz number and scattering parameters reinforces the observed modifications in the electronic structure. The simultaneous enhancement of S and electrical conductivity at x = 0.02 is attributed to the disorder-to-order transition, leading to the marked rise in PF.