Fast-fired and fine-grained pyrochlore dielectrics for optimized energy storage performance

In this study, the Fast Firing (Rapid Thermal Sintering, FF) process was applied to systematically analyze the microstructural, dielectric, and electrical properties of (Bi₁.₅Zn₀.₅)(Zn₀.₅Nb₁.₅)O₇ (BZN) ceramics. Through rapid heating, the target sintering temperature was reached within several minutes, effectively suppressing excessive grain coarsening and Bismuth (Bi) volatilization that commonly occur in conventional sintering (CS). As a result, BZN ceramics fabricated by the FF process exhibited a uniform fine-grained microstructure with grain sizes of 1–3 μm, relative densities above 94 %, dielectric constants (εᵣ) of 145–155, dielectric losses (tan δ) below 0.005, and breakdown strengths (BDS) exceeding 400 kV/cm. Energy-storage performance analysis revealed that the FF samples achieved stable energy densities of 1.25–1.37 J/cm³ and efficiencies of 75–85 %, which are attributed to enhanced BDS induced by the fine-grained microstructure. Frequency- and temperature-dependent measurements also demonstrated excellent thermal stability, maintaining tan δ < 0.005 and dielectric variation within 3 % from room temperature up to 300 °C. In addition, the FF process shortened the sintering time by more than 70 % and reduced energy consumption, offering significant advantages in processing efficiency. These results demonstrate that the FF method provides an effective fabrication strategy for achieving high-efficiency and high-reliability energy-storage performance in BZN-based pyrochlore ceramics and further suggests its potential extension to other lead-free high-permittivity dielectric systems.