Investigation of MnSc2X4 (X = S, Se) spinels to unveil their potential for optoelectronic and thermoelectric applications

Abstract

To advance the fields of optoelectronics and thermoelectrics, the demand for developing novel materials with exceptional optoelectronic and thermoelectric characteristics has greatly increased. In this respect, spinels are among the well-researched materials in the scientific community. The present study examines the mechanical, optoelectronic, magnetic, and thermoelectric characteristics of MnSc₂X₄ (X = S, Se), utilizing the WIEN2k and BoltzTrap code. The investigated materials exhibit cubic structures with the Fdm space group and lattice parameters of 10.44 and 10.94 Å for S- and Se-based compositions, respectively. Fulfillment of the Born stability criteria attest to the mechanical stability, while negative formation energies validate the thermodynamic stability of the spinels. The spin-polarized electronic band structure (EBS) and the density of states (DOS) reveal the semiconducting nature of the materials with direct bandgap (E_g). In the optical parameters, MnSc₂S₄ and MnSc₂Se₄ show a static dielectric constant of 6.5 and 8.5, respectively. The materials exhibit wide absorption spectra, ranging from visible to ultraviolet (UV) regions, with the highest absorption in the UV region. The spin-dependent volume optimization demonstrates the ferromagnetic (FM) nature of the materials. The presence of Mn ions in the compositions imparts this magnetic nature to them, which is analyzed by its high local magnetic moment. Lastly, the transport characteristics are analyzed against the increasing temperature in the range of 300–800 K. These materials exhibit high Seebeck coefficients of 242 to 251 μV K⁻¹, and their electrical and thermal conductivities increase with temperature. The figure of merit ZT showed an almost constant value at varying temperatures. The outcomes of this study demonstrate the investigated materials as potential candidates for optoelectronic and thermoelectric applications.