Effects of partial substitution of Co by Ni on structural and transport properties of TiCoSb-based half-Heusler compound

Abstract

Correlation amid structural and transport properties of TiCo(1−x)Ni x Sb, (x=0.00, 0.02, 0.04, 0.06) alloy have been investigated. Samples have been synthesized by solid state reaction method, followed by arc-melting. Minute amount of CoTi embedded phase has been revealed by in-depth structural characterization using Rietveld refinement. Unit cell volume decreases with increasing Ni in TiCo(1−x)Ni x Sb, indicate sucessful substitution. Lattice strain, crystalline size and dislocation density have been estimated from x-ray diffraction data. Temperature dependent resistivity (ρ(T)) measurements have been carried out down to 10 K. Transition from metallic to semiconducting behavior is observed in ρ(T) data for x=0.00, 0.02. ρ(T) for x=0.04 and 0.06 show metallic nature. Plausible explanation have been provided on the basis of position of Fermi surface and embedded phases.

Transport phenomena of TiCoSb: defect induced modification in the structure and density of states

“…However, the highest d for the TiCoSb 1.02 sample may be explained in light of the well-known Hall–Petch formula. According to the Hall–Petch formula, the strengthening effect of grain boundaries may be described as 75–77 σ GB = k y d −1/2 where σ GB , d , k y are yield strength at grain boundaries, crystalline size, and a material-dependent constant, respectively. Lattice mismatch at the grain boundary due to embedded phases may cause low σ GB and high d value for TiCoSb 1.02 Modified Williamson–Hall plot has been used to carry out the calculation for estimation of N D in TiCoSb 1+ x ( x = 0, 0.01, 0.02, 0.03, 0.04, 0.06) samples, employing the relation 59,78 …”

“…The r(T) data has been fitted with equation r(T) = r 0 + AT + BT 2 at low temperature (T o 150 K), where A and B represent e-ph and e-e scattering coefficients, respectively. 77,90 Non-monotonic variation of e-e and e-ph have been presented in Fig. 11.…”

“…However, the highest d for the TiCoSb 1.02 sample may be explained in light of the well-known Hall-Petch formula. According to the Hall-Petch formula, the strengthening effect of grain boundaries may be described as [75][76][77] s GB = k y d À1/2…”

“…However, the highest d for the TiCoSb 1.02 sample may be explained in light of the well-known Hall-Petch formula. According to the Hall-Petch formula, the strengthening effect of grain boundaries may be described as [75][76][77] s GB = k y d À1/2 sample. This is in agreement with the previous analysis that the presence of a minimum embedded phase with good crystal quality has been observed for the TiCoSb 1.02 sample amid synthesized samples (TiCoSb 1+x ; x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.06).…”