Electrical transport properties of TiCoSb half-Heusler phases that exhibit high resistivity

Abstract

Electrical transport measurements have been performed on doped and undoped TiCoSb half-Heusler phases. The semiconducting properties are found to be more robust than those reported for MNiSn (M = Ti, Zr, Hf ). Undoped TiCoSb phases exhibit large n-type Seebeck coefficients and high resistivities that reach −500 µV K −1 at 300 K and ∼1500 cm at 4.2 K, respectively. A tendency towards carrier localization is seen in several disordered phases. The effects due to n-type and p-type dopants are readily manifested in the thermopower, from which moderately heavy electron and hole band masses are inferred. The unusual properties measured are consistent with the prediction of a wide bandgap for the TiCoSb phase. A resistivity minimum is observed at 500-600 K for undoped and V-doped TiCoSb. Consequently, the semiconducting gap has not been determined.

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

“…The of TiCoSb, ZrCoSb and HfCoSb are larger than those of as-cast samples reported in the previous study. 11) It is well known that the annealing condition 10,[13][14][15] and the deviation from the stoichiometric composition 6) have much effect on the thermoelectric properties of the half-Heusler compounds. For example, the of TiCoSb tends to increase with decreasing the Co/Sb ratio and with increasing the Ti/Sb ratio.…”

“…[1][2][3][4][5] The theoretically calculated band gap energy of TiCoSb (0.95, 1) 0.82 eV 5) ) is larger than that of the similar material TiNiSn (0.42 eV, 1) 0.51 2) ). So, TiCoSb is expected to have a larger thermoelectric power S. From the literatures, [6][7][8][9][10][11] TiCoSb has a negative thermoelectric power. The improvement of the structural disorder 12) by annealing has been reported on MNiSn system [13][14][15] and TiCoSb system.…”

Thermoelectric Properties of Half-Heusler Type LaPdBi and GdPdBi

“…The substitution in each site is very useful for improvement of thermoelectric properties, because the position of the Fermi level in the gap can be controlled and the lattice thermal conductivity reduces due to enhancement of the phonon scattering. Since the half-Heusler compounds with 18 valence electrons have the narrow band gap near the Fermi level and show the large thermoelectric power, (Ti, Zr, Hf)NiSn, [1][2][3][4][5][6][7] (Ti, Zr, Hf)CoSb [8][9][10][11] and other half-Heusler compounds have been studied as advanced thermoelectric materials. Although high performance n-type materials in the half-Heusler compounds have been reported, 4,6) such p-type thermoelectric materials have been scarcely reported.…”

“…Similar characteristics have been reported on n-type half-Heusler compounds such as TiCoSb. 9) We have reported the thermoelectric properties of p-type half-Heusler compounds ErPdSb and ErPdBi, 15) and p-type hexagonal compounds LaPdSb and GdPdSb. 16) As mentioned above, LaPdBi and GdPdBi show high power factors at room temperature, 3) but high temperature data have not been reported.…”

Fabrication and characterization of semiconducting half‐Heusler YPtSb thin films

“…The weak temperature dependence of resistivity has also been observed in bulk YPtSb and other half-Heusler semiconductors [16], a trend markedly different from that in the case of conventional semiconductor materials such as Si. [10,[17][18][19] As seen in Fig. 3(a) the resistivity increased from 500 • C deposition temperature to 700 • C, mainly because of the decreasing carrier density with an increase in deposition temperature ( Fig.…”