Thermoelectric and Thermophysical Properties of TiCoSb-ZrCoSb-HfCoSb Pseudo Ternary System Prepared by Spark Plasma Sintering

Abstract

We studied the thermoelectric and thermophysical properties of TiCoSb-ZrCoSb-HfCoSb pseudo ternary system. Polycrystalline samples were prepared by a spark plasma sintering (SPS) technique, and their thermoelectric properties above room temperature and thermophysical properties at room temperature were measured. All the samples were identified as a half-Heusler compound by the X-ray diffraction analysis. The lattice parameter, electrical resistivity and thermoelectric power systematically change with the composition in the pseudo ternary phase diagram. All the samples indicated negative values of the thermoelectric power. Low thermal conductivity was achieved in the samples with the composition near the center of the pseudo ternary phase diagram where the effect of the alloy scattering becomes large. The maximum value of ZT was obtained to be 0.073 at 790 K for Ti 0:25 (Zr 0:5 Hf 0:5 ) 0:75 CoSb.

Thermoelectric Properties of the XCoSb (X: Ti,Zr,Hf) Half‐Heusler alloys

“…At 300 K, values of 20.8, 23.5, and 19.7 Wm −1 K −1 are obtained for TiCoSb, ZrCoSb, and HfCoSb, respectively. They agree fairly well with the largest reported experimental values of 24, 21, and 14 Wm −1 K −1 , considering the fact that is the main contributor to in semiconductors. Figure shows the reduction of due to boundary scattering as function of the grain size.…”

“…It turns out that the Debye temperature decreases for increasing atomic mass from 383 K in TiCoSb to 341 K in ZrCoSb and 316 K in HfCoSb, in agreement with the experimental situation (416 K in TiCoSb, 392 K in ZrCoSb, and 340 K in HfCoSb according to Ref. ; 396 K in TiCoSb according to Ref. ).…”

Annealing effect on the reduction of Fermi-level density of states in CoTiSb: NMR evidence

“…10,[13][14][15] There is general agreement from intense experimental results that heat treatment plays an important role for improving the structural perfection. 10,14,16,17 Observations of the enhancement in the thermal conductivity upon annealing had been attributed to the decrease in the grain-boundary and/or pointdefect scattering. 10,14,17 Nevertheless, there has been little quantitative work associated with the local properties in these half-Heusler alloys, essential to interpret the variation in their electronic characteristics through heat treatment.…”

Effect of C and N Addition on Thermoelectric Properties of TiNiSn Half-Heusler Compounds

“…The κ T of TiNiSn-1 at. % TiN is about 5.4 W/mK at 323 K, and decreases as the temperature increases, reaching 4.2 W/mK at 600 K. These values are lower than those reported across the whole temperature range [ 35 , 36 , 37 , 38 , 39 ]. The κ T is comprised of summation of κ e and κ L contributions (κ T = κ e + κ L ).…”