High structural stability, reduced lattice-thermal conductivity, and elevated energy harvesting efficiency in a Lu<sub>2</sub>CoCrO<sub>6</sub>.

Abstract

Double perovskite oxides have been emerged as promising candidates for the fast evolving technical frontier, playing a key role in the development of efficient energy conversion devices to address global energy challenges. Therefore, we theoretically examined the structural stabilities, thermoelectric, electronic, and magnetic aspects of the ordered Lu₂CoCrO₆ structure. The calculated negative formation enthalpy (-4.2 eV per atom), lack of imaginary modes in the phonon curves, and elastic constants that meet the Born conditions, confirms the thermodynamical, dynamical, and mechanical stability of the system, respectively. The material is classified as ductile by Pugh's ratio and Poisson's ratio (<i>ν</i> = 0.308 > 0.26). ratio (0.438), along with a <i>ν</i> value, which affirms ionic bonding. Also, the material exhibits a semiconducting state having direct a band-gap of 1.13 eV. The antiferromagnetic superexchange coupling between Co³⁺ (3d⁶) and Cr³⁺ (3d³) ions <i>via</i> oxygen favors the ferrimagnetic stable state. Further, the calculated partial spin magnetic moment of 3.11/-2.52 <i>µ</i> _B on the Co/Cr ion, along with an isosurface plot of the spin magnetization density, further validates the ferrimagnetic phase of the material. Interestingly, thermoelectric study demonstrates that enhanced phonon scattering causes the lattice thermal conductivity (<i>k</i>l) to drop with increasing temperature, results in a giant figure-of-merit of 1.00 at <i>µ</i> = 0.1 Ry at 700 K. Hence, these results revealed that LCCO is stable and keeps multifunctional features that may be favorable for utilization in thermoelectric and spintronic devices.