Achieving a molecular level control on surface cation segregation in double perovskite NdBaCo₂O_5+δ using dopants and strain effects

The increasing demand of clean, renewable energy is leading research interest towards solid oxide fuel cells (SOFCs). AA′Co₂O_5+δ (A= rare earth ion, and A′= alkaline earth ion) double perovskite oxides have been proposed as potential candidate for intermediate temperature SOFC cathodes [1]. Density functional and molecular dynamics theory-based simulations are performed to study the electrocatalytic and magnetic behavior of NdBaCo₂O_5+δ. Oxygen vacancy formation energies of Ba/O plane observed to be highest among different layers along (001) direction. Magnetic properties study depicts an opposite correlation between magnetic moment and oxygen vacancy formation energies. Study of different surface terminations shows Ba/Co as a stable termination. Ba cation segregation is observed to affect the surface stability of material [2,3]. Here, we put forward strain and dopant effect strategies to control and suppress the Ba cation segregation. Strain engineering offer tailoring the electrocatalytic and magnetic properties, thus opening up a pathway to improve the performance. NdBa_0.75Sr_0.25Co₂O_5+δ shows more Sr cation segregation [4]. Sr and Ca doping at A′-site resulted in the suppression of Ba cation segregation also total A′-site cation segregation. Present work focusses on understanding underlying physics of different key driving forces, suppression techniques of A′-site cation segregation in NdBaCo₂O_5+δ.