# High structural stability, reduced lattice-thermal conductivity, and elevated energy harvesting efficiency in a Lu2CoCrO6

## TL;DR

Lu2CoCrO6 is a stable double perovskite oxide with low thermal conductivity and high thermoelectric efficiency, making it promising for energy conversion devices.

## Contribution

The study reveals Lu2CoCrO6's structural stability, magnetic properties, and high thermoelectric performance through theoretical analysis.

## Key findings

- Lu2CoCrO6 is thermodynamically, dynamically, and mechanically stable with a negative formation enthalpy and no phonon instabilities.
- The material exhibits a semiconducting state with a direct band gap of 1.13 eV and a ferrimagnetic phase due to antiferromagnetic coupling.
- Thermoelectric analysis shows a giant figure-of-merit of 1.00 at 700 K due to reduced lattice thermal conductivity.

## 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 (ν = 0.308 > 0.26). ratio (0.438), along with a ν 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 via oxygen favors the ferrimagnetic stable state. Further, the calculated partial spin magnetic moment of 3.11/−2.52 µB 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 (kl) to drop with increasing temperature, results in a giant figure-of-merit of 1.00 at µ = 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.

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.