Executive Summary : | Thermoelectricity has the potential to address global energy crises and climate changes by converting waste heat into electricity. However, low efficiency has hindered their commercialization, with a figure of merit (ZT) of 3-4 needed for practical applications. Half-Heusler (HH) alloys are a promising solution due to their robust properties such as thermal stability, mechanical strength, low cost, nontoxicity, vacant lattice sites, tunable band gap, and semiconducting behavior. These alloys can sustain temperatures up to 1000 ⁰C and can be easily tailored for device applications. Recent ZT values for p-type FeNbSb, FeTaSb, and CoZrBi are impressive. However, high lattice thermal conductivity limits their applicability, and the number of semiconducting HH alloys is severely limited. Only 18 valence electron count (VEC) HH alloys qualify semiconducting behavior, and many possible 18-VEC HH compositions comprise expensive elements. Interestingly, there are many plausible 17- and 19-VEC HH alloys that can be exploited to form valence balanced compositions, forming 18-VEC, a prerequisite for semiconducting nature. The concept of disordered HH alloys is relatively new and not much explored. Limited experiments open up new horizons, but theoretical predictions can accelerate the finding of new materials. This proposal aims at density functional theory (DFT)-based investigations of new 18-VEC disordered HH alloys. The work scheme includes screening of 18-VEC HH compositions, predicting their stability, studying stable systems for ground state properties, sorted out stable nonmagnetic semiconductors for favorable electronic structure, and studying electrical and thermal transport properties. |