Tailoring High Energy Storage Density by a Temperature-Induced Relaxor-to-Ferroelectric Phase Transition

Crystallization temperature was tuned to control the crystal structure and relaxor behavior of Na0.5Bi5.5Ti4AlO18 films. This established a structure–property regulation pathway, enabling controlled transitions from ferroelectric, non-ergodic relaxor to ergodic relaxor states. Precise crystallization temperature control reduced grain size, thereby increasing both bulk resistivity and breakdown strength via suppressed conduction pathways. The Na0.5Bi5.5Ti4AlO18 film achieves outstanding energy storage performance when crystallized at 500 °C, delivering a recoverable energy density of 49.6 J/cm3 and an energy efficiency of 73.5% at an applied electric field of 2820 kV/cm. It also exhibits excellent thermal and frequency stability. Thus, crystallization temperature control is a direct, effective lever for optimizing dielectric energy storage films.