Experimental Realization of Heavily p-doped Half-Heusler CoVSn Compound

Sadeq Hooshmand Zaferani,Reza Ghomashchi,Soon-Jik Hong,Daryoosh Vashaee,Alireza Darebaghi

doi:10.3390/en13061459

Sadeq Hooshmand Zaferani, Reza Ghomashchi + Show 3 more

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https://doi.org/10.3390/en13061459

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Abstract

Hypothetical half-Heusler (HH) ternary alloy of CoVSn has already been computationally investigated for possible spintronics and thermoelectric applications. We report the experimental realization of this compound and the characterizations of its thermoelectric properties. The material was synthesized by a solid-state reaction of the stoichiometric amounts of the elements via powder metallurgy (30 h mechanical milling and annealing at 900 °C for 20 h) and spark plasma sintering (SPS). The temperature-dependent ternary thermodynamic phase diagram of Co-V-Sn was further calculated. The phase diagram and detailed analysis of the synthesized material revealed the formation of the non-stoichiometry HH CoVSn, mixed with the binary intermetallic phases of SnV3, Co2Sn, and Co3V. The combination of X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermoelectric transport properties confirmed the formation of a multi-phase compound. The analysis revealed the predicted thermoelectric features (zT = 0.53) of the highly doped CoVSn to be compromised by the formation of intermetallic phases (zT ≈ 0.007) during synthesis. The additional phases changed the properties from p- to overall n-type thermoelectric characteristics.

Highlights

There have been substantial progress in thermoelectric (TE) materials over the last two decades.Thermoelectric technology, which was mainly based on alloys of bismuth telluride [1] for Peltier cooling modules, or silicon-germanium alloys [2] for radioisotope thermoelectric generators used in NASA spacecraft, has expanded to new compounds for power generation and cooling [3].New materials and material structures have been discovered with considerably enhanced thermoelectric properties [4]
These diagrams further confirm that at thermodynamic equilibrium, the material decomposes into multiple phases, as listed in Table 3, which agrees with the observation in the microstructural analysis (Figures 3 and 4)
According to the theoretical and experimental data presented here, the CoVSn phase was found to be thermodynamically unstable, and its partial decomposition into metallic phases is unavoidable at the equilibrium state

Summary

Introduction

There have been substantial progress in thermoelectric (TE) materials over the last two decades. In 1995, Ö güt et al [36] predicted CoVSn with a MgAgAs (C1b) crystal structure as an applied the full-potential linear muffin-tin orbital (FP-LMTO) method to evaluate the electronic intermetallic semiconductor using density functional theory (DFT) band structure calculations. Based on this electronic structure, the alloy was predicted as a p-type semiconductor transport calculations. (DOS) of CoVSn alloy [38] Based on this electronic structure, the alloy was predicted as a p-type semiconductor with a bandgap (W-X) of 0.85 eV. Calculated electronic band structure and density of states (DOS) of the CoVSn alloy.

Materials and Methods

Discussion

Conclusions