Paraelectric Matrix-Tuned Energy Storage in BiFeO₃–BaTiO₃–SrTiO₃ Relaxor Ferroelectrics

Incorporation of polymorphic ferroelectric nanodomains into a paraelectric matrix has been proven to be effective to achieve high energy storage density in a relaxor ferroelectric system. In this work, we fabricated short-range ordered polymorphic 0.20BiFeO₃–(0.80 – x)­BaTiO₃ nanodomains in a paraelectric xSrTiO₃ host (0.40 ≤ x ≤ 0.65) to form ternary relaxors with transition temperatures in the range of 425–460 °C. The addition of SrTiO₃ suppresses the P–E loops of the binary BiFeO₃–BaTiO₃ system and improves the recoverable energy and energy storage efficiency. A well-sintered solid solution exhibits nearly ideal relaxor ferroelectric behavior for x = 0.50, which demonstrates the highest tetrahedral c/a ratio (1.0042), saturation polarization (26.39 μC/cm²), breakdown strength (183.1 kV/cm), and recoverable energy (2.15 J/cm³ at 190 kV/cm) and also shows high current density, high power density, and short discharge time. The overall evolution of the c/a ratio, saturation polarization, and recoverable energy follows an x-dependent volcanic shape, while the variation of residual polarization is x-independent. The maximum energy storage efficiency of 95.56% is observed for x = 0.55 at 200 kV/cm. These findings suggested that the 0.20BiFeO₃–(0.80 – x)­BaTiO₃–xSrTiO₃ system is promising for dielectric energy storage applications.