Improving energy storage density, piezoelectric, and energy harvesting performances of eco-friendly (Bi0.49-xBaxLa0.01Na0.40K0.10)TiO3 ceramics by composition design strategy

In this research, eco-friendly (Bi0.49-xBaxLa0.01Na0.40K0.10)TiO3 or BiBaxLNKT ceramics (where x = 0-0.15 mol fraction) were fabricated by solid-state mixed oxide technique, and their phase evolution, physical, microstructure, mechanical, dielectric, piezoelectric, ferroelectric, energy storage density, and energy harvesting properties have been systematically investigated. All ceramics exhibited a single perovskite structure. With increasing Ba content, a phase transition from mixed rhombohedral-tetragonal to be more tetragonal-rich phase was observed. The addition of Ba inhibited grain growth and resulted in densification, mechanical, and dielectric improvement. The maximum values of HV (6.01 GPa), HK (5.78 GPa), E (78 GPa), KIC (1.38 MPa.m1/2), epsilon r (1604), and tan delta (0.0504) were observed for the x = 0.15 ceramic. The x = 0.15 ceramic also showed excellent piezoelectric performances (d33 = 248 pC/N, g33 = 17.46 x 10-3 Vm/N, and kp = 49%) and good off-resonance figure of merit (FoM) for energy harvesting (4.33 pm2/N). Moreover, after the introduction of Ba content, the ferroelectric long-range order is broken, which contributes to energy storage density improvement. Especially, the x = 0.05 ceramic achieved excellent recoverable energy storage density (Wrec = 1.31 J/cm3) and good energy storage efficiency (eta = 96.18%) at 150 degrees C under driving electric fields (E) of 75 kV/cm. All results indicated that we can efficiently fabricate an environment-friendly (Bi0.49-xBaxLa0.01Na0.40K0.10)TiO3 system with good reliability for energy harvesting and high-temperature energy storage capacity applications.