MnNiSi Half-Heusler Alloy: Computational and experimental insights for energy harvesting and spintronic applications

Abstract

The MnNiSi half-Heusler alloy was synthesized via solid-state synthesis for thermoelectric and spintronic applications and extensively characterized using various techniques. X-ray diffraction (XRD) confirmed the alloy's cubic crystal structure with three interpenetrating face-centered cubic sublattices and a lattice parameter of 5.1592 Å. Field emission scanning electron microscopy (FE-SEM) revealed a polycrystalline nature with grains of varying shapes and sizes, while energy-dispersive X-ray spectroscopy (EDX) verified compositional homogeneity. Optical characterization using UV–Vis spectroscopy identified a broad absorption peak at 278 nm, and the optical bandgap energy (E_g) was calculated as 0.57 eV from the Tauc plot, indicating semiconducting behaviour. Fourier-transform infrared (FTIR) spectroscopy highlighted vibrational modes associated with organic and inorganic components. Mechanical analysis demonstrated stability with Debye and melting temperatures of 505 K and 1244 K, respectively. The magnetic characteristics of the MnNiSi half-Heusler demonstrate the material's Ferromagnetic (FM) behaviour. The thermoelectric evaluation showed a Seebeck coefficient of 118 µV/K, electrical conductivity of 1.08 × 10³ Ω^-1m^-1, a thermal conductivity of 2.18 W/mK, and a power factor of 15.27 × 10^–3W/mK². These properties yielded a dimensionless figure of merit (ZT) of 1.52, highlighting MnNiSi as a promising candidate for thermoelectric energy conversion applications.