Stabilizing low-loss pyrochlore phase for high-efficiency energy storage

Bismuth-based pyrochlore phases, as linear dielectrics, offer a compelling combination of ultralow loss, moderate permittivity, and high breakdown strength, rendering them promising for dielectric energy storage applications. However, the advancement of related research is impeded by the inherent thermodynamic instability in the Bi2O3–TiO2 phase diagram, which makes the synthesis of phase-pure Bi2Ti2O7 particularly challenging. In this work, we demonstrate that the stability of Bi2Ti2O7-based phase is significantly enhanced through careful control of the thermal processing temperature. The resulting materials, therefore, show ultralow dielectric loss and reduced polarization switching hysteresis as well as improved breakdown field. Consequently, a high energy density of 65.5 J/cm3 and an excellent energy efficiency of 84.3% are achieved concurrently. The findings reported herein help to elucidate the relationship between pyrochlore structure stabilization and thermal treat process, thereby providing an effective way for improving the energy storage performance of Bi2Ti2O7-based thin films.