Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (W rec) and high ES efficiency (eta) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (Delta P) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O-3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (E-b) and enhance Delta P. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable W rec of 6.85 J/cm(3) and eta of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in W rec (3.0%) and eta (4.4%) over the temperature range of 20-110 C-degrees. Additionally, BNKT-0.15SLZT(VPP) exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm(3), a large power density of 164.2 MW/cm(3), and a short discharge time (t 0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZT(VPP) for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.