Tailoring phase transitions and enhanced energy storage properties of LiTaO₃-modified Bi_0.5Na_0.25K_0.25TiO₃ lead-free ceramics for next-generation actuators

This study investigated eco-friendly binary solid solution system (1-x)(Bi_0.5Na_0.25K_0.25TiO₃)–(x)LiTaO₃ (BNKT-xLT, x = 0.05, 0.10, 0.15, 0.20, and 0.25) piezoceramics synthesized via the conventional solid-state reaction method. Systematic characterization revealed that the addition of x(LT) influenced the microstructural characteristics, phase transitions, and electromechanical properties of the ceramic. Notably, the investigated piezoceramics exhibited a morphotropic phase boundary (MPB), which enhanced their piezoelectric performance, as confirmed by X-ray diffraction (XRD), dielectric, and ferroelectric measurements. The optimal composition, 95BNKT-05LT, achieved a remarkable static piezoelectric constant (d₃₃) of 168 pC/N and a normalized piezoelectric strain ((Formula presented) of ≈782 pm/V under an applied electric field (E) of 70 kV/cm. Furthermore, the energy storage density of the 95BNKT-05LT composition was approximately 0.437 J/cm3 at a frequency of 10 Hz, with an energy-storage efficiency of ≈54 %. These results revealed the potential of the synthesized lead-free piezoceramics for next-generation high-temperature actuator and capacitor applications, thereby contributing significantly to the development of sustainable and environmentally benign piezoelectric technologies.