A Systematic Approach for Semiconductor Half-Heusler

Abstract

The key to designing a half-Heusler begins from the understanding of atomic interactions within the compound. However, this pool of knowledge in half-Heusler compounds is briefly segregated in many papers for specific explanations. The nature of the chemical bonding has been systematically explored for the large transition-metal branch of the half-Heusler family using density-of-states, charge-density, charge transfer, electron-localization-function, and crystal-orbital-Hamilton-population plots. This review aims to simplify the study of a conventional 18-electron configuration half-Heusler by applying rules proposed by renowned scientists to explain concepts such as Zintl-Klemm, hybridization, and valence electron content (VEC). Atomic and molecular orbital diagrams illustrate the electron orbital transitions and provide clarity to the semiconducting behavior (VEC = 18) of half-Heusler. Eighteen-electron half-Heusler usually exhibits good thermoelectric properties owing to favorable electronic structures such as narrow bandgap (<1.1 eV), thermal stability, and robust mechanical properties. The insights derived from this review can be used to design high-performance half-Heusler thermoelectrics.

A first-principles assessment of the thermoelectric properties in half-heusler compound NbIrSn

“…The symmetric and equal distribution of electron spins within the mentioned orbitals leads to the cancellation of magnetic moments and hence plays a crucial role in the absence of magnetic behavior in the NbIrSn compound. The non-magnetic and semiconducting properties observed in a HH NbIrSn is in accordance with the predictions made by the Slater-Pauling rule [21]. To better understand the material's conversion efficiency, it is necessary to quantify various transport coefficients, which can provide insights into its performance.…”

“…Our calculations include the valence electronic configuration of constituent atoms Nb: 4d 4 5s 1 , Ir: 5d 7 6s 2 , Sn: 5s 2 5p 2 which yield a total of 18 valence electron count. Based on the valence electron count, it can be presumed that NbIrSn is likely a nonmagnetic semiconductor with a magnetic moment of 0.0 μ B from Slater-Pauling rule [21], that states the magnetic moment (M) of a material is determined by the number of valence electrons (Z) in the unit cell and is given by M = (Z-18)μ B . Figure 2.…”

Lattice thermal conductivity in half-Heusler compounds XNiSn (X=Ti, Zr, Hf) using Slack's model

“…Symmetric and equal electron spin distribution in mentioned orbitals cancels magnetic moments, that explains the non-magnetic behavior in XNiSn compounds. The non-magnetic behavior in these 18 VEC hH is in agreement with the Slater-Pauling rule [43], which connects the material's magnetic moment (M) to the number of valence electrons (Z) in the unit cell as M= (Z-18)µ B .…”

Magnetically Enhanced Thermoelectric Performance of Ti0.75NiSb+x mol % Fe (x = 0–5) Nanocomposites

“…Half-Heusler (HH) compounds are promising candidates for medium- to high-temperature thermoelectric applications. , They have a MgAgAs face-centered cubic crystal structure with the F 4̅3 m space group. , The chemical formula of HH compounds is ABX , where A is a transition element with strong electronegativity, such as Ti, Zr, and Hf; B is a transition element with weak electronegativity, such as Fe, Co, and Ni; and X is the main group element, such as Sn and Sb . In the HH system, A and X atoms form the NaCl structure, and half of the cubic interval is occupied by B atoms and the other half is not filled .…”