Improvement of electric field-induced strain and energy storage density properties in lead-free BNKT-based ceramics modified by BFT doping

Abstract

In this research, the effects of Ba(Fe_0.5Ta_0.5)O₃ (BFT) additive on the phase evolution, the dielectric, ferroelectric, piezoelectric, electric field-induced strain responses, and energy storage density of the Bi_0.5(Na_0.80K_0.20)_0.5TiO₃–0.03(Ba_0.70Sr_0.03)TiO₃ (BNKT–0.03BSrT) ceramics have been systematically investigated. The ceramics have been prepared by a solid-state reaction method accompanied by two calcination steps. X-ray diffraction indicates that all ceramics coexist between rhombohedral and tetragonal phases, where the tetragonal phase becomes dominant at higher BFT contents. The addition of BFT also promotes the diffuse phase transition in this system. A significant enhancement of electric field-induced strain response (S_max = 0.42% and = 840 pm V⁻¹) is noted for the x = 0.01 ceramic. Furthermore, the giant electrostrictive coefficient (Q₃₃ = 0.0404 m⁴ C⁻²) with a giant normalized electrostrictive coefficient (Q₃₃/E = 8.08 × 10⁻⁹ m⁵ C⁻² V⁻¹) are also observed for this composition (x = 0.01). In addition, the x = 0.03 ceramic shows good energy storage properties, i.e. it has a high energy storage density (W = 0.65 J cm⁻³ @ 120 °C) with very high normalized storage energy density (W/E = 0.13 μC mm⁻²), and good energy storage efficiency (η = 90.4% @ 120 °C). Overall, these results indicate that these ceramics are one of the promising candidate piezoelectric materials for further development for actuator and high electric power pulse energy storage applications.