Time Dependence of Kinetic Unmixing and Kinetic Decomposition of a Perovskite ABO3 under Applied Voltage—A Case Study for BaTiO3

Abstract

AbstractIn multinary oxides such as perovskites ABO3, an applied voltage causes charged mobile species (ions, electrons) to move according to their electrochemical mobilities. For different electrochemical mobilities of the cations kinetic unmixing takes place, and after some time even kinetic decomposition may occur. Both kinetic effects are detrimental to the functional application of the oxide, for example, in electrochemical cells or in multilayer ceramic capacitors. Thus far, kinetic unmixing and decomposition are analyzed by treating ABO3 only as a quasi‐binary mixture of AO and BO2, acceptors are not considered, and only the steady state of kinetic unmixing is investigated, allowing no prediction of the lifetime until kinetic decomposition. Here, ABO3 is treated as a really ternary system with defects in all three sublattices and with electronic defects. The complete set of transport equations is derived, and the moving boundary problem with six mobile species is solved numerically to investigate the time‐dependence of kinetic unmixing. As a case study, BaTiO3 is used which has various applications as a functional oxide. The simulations yield the kinetic decomposition voltage of the oxide, below which no kinetic decomposition occurs. For voltages larger than this critical value the lifetime of the oxide until kinetic decomposition is predicted.