Molecular Dynamics Simulation on Oxide Ion Conduction of La-Based Perovskite Oxides for SOFCs Electrolyte

La-based perovskite oxides have various physical and electrical properties by substitution of various elements at A and/or B-sites. Especially, doping of low-valent cation generates oxygen vacancies to maintain charge neutrality, leading to high oxide ion conductivity. Also, B-site is comprised of transition metals such as Co, Mn or Fe, the La-based perovskite oxides become a mixed ionic-electronic conducting material. So, these La-based perovskite oxides can be applied to electrode, electrolyte or interconnect materials of solid oxide fuel cells (SOFCs). Recently, the SOFCs operating temperature is getting lower, much attention has been paid to the La-based perovskite oxides to alternate a conventional electrolyte material, yttria-stabilized zirconia (YSZ). To obtain an optimal La-based perovskite oxide with high oxide ion conductivity, it is very important to understand a correlation between experimental variables such as dopant type or concentration and various factors affecting the electrical conductivity. Therefore, we microscopically analyzed the effects of A-site dopant types and B-site cation types in LaInO₃ perovskite oxide with orthorhombic structure on the oxide ion conductivity using molecular dynamics simulation. La_0.9A_0.1InO_2.95 (A=Ca, Sr and Ba) and La_0.9Sr_0.1MO_2.95 (In, Ga and Sc) compositions were modeled. The pair potential used in this study has two parts. One part represents long-range interaction described by Coulombic force. The other part represents short-range interaction by Born-Mayer-Huggins pair potential. The simulation box consisted of a total of 3960 atoms with periodic boundary conditions. Main calculations were carried out for 1.6ns with time step of 1fs after relaxation under NPT ensemble. From the radial distribution function results, it was found that the interionic distance between oxide ion and A-site dopant is important factor determining the ionic conductivity.