Structural, Chemical, Electrical, and Thermal Properties of n-Type NbFeSb

Abstract

We report on the structural, chemical, electrical, and thermal properties of n-type polycrystalline NbFeSb synthesized by induction melting of the elements. Although several studies on p-type conduction of this half-Heusler composition have recently been reported, including reports of relatively high thermoelectric properties, very little has been reported on the transport properties of n-type compositions. We combine transport property investigations together with short-and longrange structural data obtained by Mössbauer spectroscopy of iron-57 and antimony-121 and by neutron total scattering, as well as first-principles calculations. In our investigation, we show that n-type conduction can occur from antiphase boundaries in this material. This work is intended to provide a greater understanding of the fundamental properties of NbFeSb as this material continues to be of interest for potential thermoelectric applications.

Defect charging and resonant levels in half-Heusler Nb$_{1-x}$Ti$_x$FeSb

“…4(b), gradually decreasing with temperature increasing. The main line shift is 0.089 mm s −1 at 295 K and 0.194 mm s −1 at 80 K. These results are very similar to the results recently reported [30] for an n-type NbFeSb sample. A fit to a standard second-order doppler relation [31], shown in Fig.…”

“…Besides our work, Hobbis et al [30] also reported 57 Fe Mössbauer spectroscopy of NbFeSb, however in contrast with the p-type NbFeSb-1050 sample, their work focused on n-type NbFeSb. For n-type NbFeSb, two extra small doublets were observed with positions that differ from that of our measured satellite (0.65 mm s −1 ).…”

Unveiling the phonon scattering mechanisms in half-Heusler thermoelectric compounds

“…A similar refinement was performed for NbFeSb to quantify the Fe/4d Frenkel defects. 62 On the other hand, refining the Sn-free compounds (Zr 0.8 Ti 0.2 CoSb and ZrCoSb) ends up with physically meaningless results (negative occupation at the 4d sites) if the Co/4d defects are permitted. Therefore, the point-defect feature of the Sn-containing compounds is essentially different from the Sn-free ones.…”

Synergistic defect engineering for improving n-type NbFeSb thermoelectric performance through high-throughput computations

“…This is consistent with the experimentally suggested intrinsic defects of Fe Nb or Fe i in NbFeSb. 20,21,37 Their donor behaviors imply the n-type character of the intrinsic NbFeSb compound. The formation of Fe i at the Fermi level close to the CBM is compensated by the formation of Fe Nb neutral defect, resulting in n-doped behavior.…”

“…In 2019, Zhu et al successfully synthesized the corresponding n-type NbFeSb-based TE materials by substituting Co or Ir for Fe sites. Unfortunately, the maximum ZT value is quite low, ∼0.5 at 1000 K, [20][21][22] which is due to the poor electrical conductivity and low solid solubility of the dopants at the Fe sites. Until now, only the p-type NbFeSb compounds have been widely investigated, [23][24][25][26] and the corresponding n-type compounds are still scarce with much lower ZT value.…”