Titanate-based high-entropy perovskite oxides relaxor ferroelectrics

Different combinations of monovalent and trivalent A-cations in high-entropy perovskite oxides (HEPOs) were investigated. The multicomponent (A'_0.2A″_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃ (A' = Na⁺, K⁺, A″ = Bi³⁺, La³⁺) perovskite compounds were successfully synthesized by solid-state reaction method persisting average cubic perovskite phase. The trivalent cation exhibited distinct effects on local structure, dielectric properties and relaxor ferroelectric behavior. Highly dense ceramics (> 95%), high dielectric constant (~ 3000), low dielectric loss (~ 0.1), and relaxor ferroelectric characteristics were obtained in the compound containing Bi³⁺. The La³⁺ containing compounds revealed lower dielectric constant, higher dielectric loss and linear dielectric behavior. The effect of monovalent cation on the dielectric properties was minimal. However, it affected relaxor ferroelectric behavior at elevated temperatures and conduction behavior at high temperatures. The (K_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃ ceramic maintained the relaxor ferroelectric behavior with low P_REM at high temperatures suggesting more stable relaxor ferroelectric characteristics than that of the (Na_0.2Bi_0.2Ba_0.2Sr_0.2Ca_0.2)TiO₃. Moreover, between these two compounds, the homogeneous electrical characteristics could be obtained from the compound consisting of K + and Bi + at A-site. This study suggests that tuning the chemical composition, particularly choosing appropriate combination of mono/trivalent cations in high entropy perovskite oxides, could be the effective approach to develop high-performance relaxor ferroelectrics with the desired properties.