Fundamentals and practical dielectric implications of stoichiometry and chemical design in a high-performance ferroelectric oxide: BaTiO₃

The processing science and fundamental understanding of defect chemistry of BaTiO₃ is a model example of how material science is used to guide the materials engineering of capacitive devices. The fundamentals are discussed from the phase equilibria, defect chemistry, and the impact on intrinsic properties. We reviewed the phenomenological defect chemistry approaches and considered the importance of doping strategies and the formation of associated point defect complexes. First principles calculations have proven to be a most informative strategy towards understanding these complexes and implications conduction mechanism. The nature of mixed conduction is considered with various dopants in the BaTiO₃ and conditions that can arise with different oxygen vacancy concentrations over a wide range of conditions. Defect dynamics are considered experimentally in terms of associations and dissociations kinetics of oxygen vacancies from these various complexes. The deleterious impact on time-dependent properties is reviewed, including time-dependent dielectric breakdown, fatigue, and aging.