Defect mechanisms, oxygen vacancy trapping ability in rare‐earth doped BaTiO3 from first‐principles and thermodynamics

Abstract

AbstractThe defect mechanisms of rare earth (RE) doped BaTiO3 have a strong impact on the electrical performance of the multilayer ceramics capacitors (MLCCs). Oxygen vacancy is the main reason for the device degradation over longtime use, while the effect of the doping strategy on controlling the oxygen vacancies is not yet quantitatively understood. In this work, the grand canonical thermodynamic defect model based on first‐principle calculations is applied to evaluate the defect mechanism of RE‐doped BaTiO3 under practical experimental condition. The charge compensation and prior site occupancy of RE are found not only associated with ionic size but also exhibit transitions with oxygen partial pressure and doping concentration. Furthermore, the oxygen vacancy trapping ability of RE ions is evaluated from the perspectives of thermodynamics and kinetics. The migration barrier among first nearest oxygen sites dramatically changed depending on the RE site occupancy. The large trapping ability is contributed by the relatively large negative binding energy of the defect complex and comparable RE concentrations substituted on Ba and Ti sites. The two conditions can be achieved in amphoteric ions doped systems, while in pure donor doped BT only one of these conditions can be satisfied. Although the self‐compensated defect complexes exhibit the highest binding energy, the trapping ability contributed by different defect complexes (, , REBa − RETi) is generally comparable in these systems. This feature of amphoteric RE ions accounts for the improvement of the lifetime and reliability of MLCCs.