Scrutinizing the stability and exploring the dependence of thermoelectric properties on band structure of 3d-3d metal-based double perovskites BaFeNiO and BaCoNiO.

Through the conventional DFT computation, we have designed new oxide double perovskites BaFeNiO and BaCoNiO. The structural and thermodynamic stabilities are predicted by optimizing the crystal structure and evaluation of enthalpy of formation, respectively. Then by using the optimized lattice constant, we have explored the different physical properties. The GGA + mBJ electronic band-structure illustrates BaFeNiO is a half-metal with 100% spin polarization at the Fermi level. While BaCoNiO shows a ferromagnetic semiconducting nature. The change in the electronic structure when Fe is replaced by Co is explained with the help of the orbital diagram and exchange interaction. The e-e hybridization that happens via O-p states is strong because Fe-O-Ni and Co-O-Ni bond angles are strictly 180°. The narrow bandgaps in the semiconducting channels prompted us to analyze the applicability of these materials towards thermoelectric technology. Besides this, we have investigated the dependency of transport properties on electronic band structure. The semiconducting nature in BaCoNiO results in a significant ZT around 0.8 at room temperature makes it suitable for wasted-energy regeneration.