Preparation and study of La-doped bismuth sodium potassium titanate -strontium titanate piezoelectric ceramics to enhance energy storage properties

This study involves the introduction of lanthanum oxide into bismuth sodium potassium titanate, alongside strontium titanate, denoted by the La2O3-doped BNKT-ST samples with varied x values ranging from 0.000 to 0.030 mol % prepared by conventional solid-state reaction technique. The research comprehensively investigates the impact of lanthanum incorporation on the phase evolution, dielectric properties, scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDAX), ferroelectric behavior, piezoelectric response, and energy storage density of the Bi0.5(Na0.84K0.16)0.5TiO3-SrTiO3 (BNKT-BST) ceramics. Powder X-ray diffraction analysis reveals a tetragonal phase structure in all ceramics. Scanning Electron Microscopy (SEM) is employed for surface morphology analysis, indicating that higher concentrations of lanthanum result in reduced grain sizes. The ceramic material demonstrates remarkable P-E hysteresis loops, featuring a prominent peak at an electric field intensity of 3 kV/cm. The trends in residual polarization (Pr) and coercive field (Ec) show ascending, descending, and subsequent ascending patterns with increasing lanthanum concentration. Dielectric measurement was carried out for different composition at various temperatures. The maximum dielectric constant (εr) ∼ 4553 was observed at 348 oC. The sample was poled at a voltage of 3-5 kV. Notably, at a La doping level of 0.020 mol%, the doped samples exhibit favorable performance, as evidenced by the highest piezoelectric coefficient (d33) of 121 pC/N observed in the poled samples. The 0.97BNKT-0.030ST ceramics showcase exceptional energy storage capacity, marked by an elevated energy storage density (W) of 0.26 J/cm3 and a notable energy storage efficiency of 58 %. This study suggests the promising application potential of lanthanum-doped BNKT-ST ceramic capacitors, which are lead-free and exhibit high power density energy storage. Consequently, the BNKT-ST ceramic material emerges as a prospective candidate for further development in actuator and energy storage applications.