From ferroelectricity to relaxor behavior: Defect-mediated functionalization of barium titanate

As the core dielectric material in multilayer ceramic capacitors (MLCC), barium titanate (BaTiO₃) exhibits conventional ferroelectric behavior that is inherently limited by temperature sensitivity, high dielectric loss, and reliability concerns. In recent years, the coupling mechanism between defect engineering and relaxor ferroelectric behavior has provided a breakthrough direction for the functionalization of BaTiO₃. This review systematically summarizes the regulatory roles of both intrinsic and extrinsic defects on the polarization behavior of BaTiO₃. It elucidates how defect-induced dynamic disorder of nanoscale polar regions facilitates relaxor ferroelectric behavior. By contrasting the mechanisms of donor and acceptor doping, the “double-edged sword” effect of defects is clarified. Furthermore, the potential for optimizing defect distribution through nanostructuring and core–shell architecture design is discussed, as well as the detrimental impact of hydroxyl defects on high-frequency performance. Despite notable progress in correlating defect engineering with relaxor behavior, challenges remain, including the lack of quantitative models for doping and the need for further optimization of performance coupling. In the future, the integration of multiscale simulations is expected to drive the development of BaTiO₃-based MLCC towards ultrahigh stability, low loss, and adaptability to extreme environments.