Abstract
The effects of V vacancy on the thermoelectric performance of the half-Heusler compound VCoSb have been investigated in this study. A certain amount of CoSb secondary phase is generated in the VCoSb matrix when the content of V vacancy is more than 0.1 at%. According to the results, a ZT value of 0.6, together with a power factor of 29 μW cm−1 K−2 at 873 K, were achieved for the nonstoichiometric sample V0.9CoSb. This proved that moderate V vacancy could improve the thermoelectric (TE) properties of VCoSb. The noticeable improvements are mainly owing to the incremental Seebeck coefficient, which may benefit from the optimized carrier concentration. However, too much V vacancy will result in more CoSb impurity and deteriorate the TE performances of VCoSb owing to the increased thermal conductivity.
Highlights
Thermoelectric (TE) materials are a type of functional material that can be used to directly convert thermal energy into electrical energy through the motion of internal carriers in solids
Was achieved for Nb0.83 CoSb [29]. We focus on another HH compound, the thermoelectric material VCoSb with nominal
Extremely weak impurity peaks of CoSb phase can be found in the V0.9 CoSb sample, the stoichiometric VCoSb sample and the nonstoichiometric V0.95 CoSb sample were found to be pure in phase
Summary
Thermoelectric (TE) materials are a type of functional material that can be used to directly convert thermal energy into electrical energy through the motion of internal carriers in solids. The properties of HH compounds are strongly influenced by the number of valence electrons in a unit cell; HH compounds with a number of 18 valence electrons are typically semiconductors, and MI NiSn, MI CoSb (MI = Ti, Zr, Hf), MII FeSb (MII = Nb, V), and their alloys have been extensively investigated as promising TE materials applicated at medium-high temperature [13,14,15,16,17,18,19,20,21,22]. Experiments have confirmed that NbCoSb and VCoSb, with a cubic HH structure and 19 valence electrons per unit cell, exhibit moderate n-type TE properties and achieve a ZT value of about 0.4 and 0.5 at 973 K [23,24]. Zhu et al confirmed experimentally that Nb0.8 CoSb is a stable HH compound, and the carrier concentration can be improved by the content of Nb vacancy.
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