Enhancing dielectric properties of BaZrTiO3 via controlled anatase/rutile core-shell TiO2

Abstract

Numerous studies are being conducted to develop novel materials capable of achieving ultrahigh dielectric constants. In this research, we focused on controlling oxygen vacancies and grain growth in dielectric materials to enhance their dielectric properties. To achieve this, we successfully manipulated the crystal structure of TiO₂ in the perovskite structure using a core-shell approach. This innovative method allowed us, for the first time, to regulate both oxygen vacancies and grain growth during solid-state synthesis. After heat-treating metastable anatase TiO₂ to form an anatase/rutile core-shell structure, it was used as a precursor for Ba–Zr–TiO₃ solid-state synthesis. At the optimal conditions for the anatase/rutile core-shell (87% rutile and 13% anatase), the electron excitation in TiO₂ between the stable phase (rutile) and the metastable phase (anatase) generates localized Ti³⁺. The resulting oxygen vacancies induce the formation of electron-pinned defect clusters, which are a significant cause of the ultrahigh dielectric constant in barium zirconate titanate.