Boosted Energy Storage Densities in Lead-Free Na0.5bi0.5tio3-Based Thick Film Ceramics Via the Compositional and Microstructural Tailoring

Abstract

Developing ecologically benign lead-free dielectrics with overall outstanding energy storage properties (ESP) is a fundamentally significant demand and challenge for the applications in pulse power systems. Herein, a new type of lead-free (0.74-x)Bi0.5Na0.5TiO3-0.06BaTiO3-0.2SrTiO3-xBi(Mg0.5Zr0.5)O3 (NBT-xBMZ) relaxor ferroelectric thick film ceramics were designed and prepared via compositional and microstructural optimization. Doping Bi(Mg0.5Zr0.5)O3 (BMZ) effectively widened the bandgap, introduced polar nanoregions, enhanced the relaxor ferroelectric characteristics, improved the impedances, and ultimately improved the dielectric breakdown strength (DBS) as well as the ESP. As confirmed by both the selected area electron diffraction patterns and the Rietveld refinement of X-ray diffraction patterns, multiphase coexistence structure was successfully constructed, resulting in merged polarization and delayed polarization saturation. Multiphase coexistence structure, pinched polarization-electric field hysteresis loops and ultrahigh DBS collectively boost the ESP. Remarkably, a recoverable energy storage density of 15.79 J/cm3 and an energy storage efficiency of 92.86% were achieved in NBT-0.22BMZ thick film. Benefiting from the microstructural optimization, excellent thermal stability (20–160 °C), frequency stability (1–200 Hz), and fatigue endurance (> 104 cycles) were realized for the same composition. Additionally, the NBT-0.22BMZ thick film also exhibited a large power density of 582.47 MW/cm3 and an ultrafast discharge speed of ~44.0 ns. This work provides a novel strategy to develop next-generation dielectric capacitors with superior energy storage properties for applications in advanced pulse power systems.

Keywords: Lead-free, Na0.5Bi0.5TiO3-based thick film ceramics, Tape-casting method, multiphase coexistence, Energy storage density, Energy storage efficiency