Yielding optimal dielectric energy storage and breakdown properties of lead-free pyrochlore ceramics by grain refinement strategies

In the quest to develop high-performance dielectrics suitable for high-power applications, its microstructure engineering and understanding the effect on the property have become crucial. However, the trade-off relationship between saturated polarization and breakdown strength with respect to the average grain size complicates defining the ideal microstructure for high-performance energy storage dielectrics. In this study, we investigates the impact of the microstructure of (Bi_1.5Zn_0.5)(Zn_0.5Nb_1.5)O₇ (BZN) pyrochlore ceramics on their energy storage characteristics by adjusting sintering temperatures. Interestingly, dielectric properties, energy storage capabilities, and electrical fatigue characteristics exhibit minimal change, maintaining a high dielectric constant (∼160) and a low dielectric loss (< 10⁻⁴). Moreover, BZN ceramics demonstrate quasi-linear dielectric properties up to 250 kV cm⁻¹, with slight fluctuation in energy density as the function of grain size (1.08–1.26 J cm⁻³). This weak dependence of energy storage on microstructure underscores that the enhancement of BZN ceramics for energy storage devices is more effectively achieved by improving breakdown strength through microstructural refinement rather than grain enlargement, which has limited impact on energy density in BZN systems. The findings from this study offer valuable insights into optimizing the microstructures of multilayer systems that are targeted at augmenting volumetric energy density, laying the groundwork for further advancements in dielectric materials.