Polar Vortices in Relaxor Ferroelectric Ceramics for High-Efficiency Capacitive Energy Storage

Polar vortices are predominantly observed within the confined ferroelectric films and the ferroelectric/paraelectric superlattices. This raises the intriguing question of whether polar vortices can form within relaxor ferroelectric ceramics and subsequently contribute to their energy storage performances. Here, we incorporate 10 mol % CaSnO 3 into the 0.7NaNbO 3 -0.3Sr 0.7 Bi 0.2 TiO 3 matrix, yielding a coexistence of phases: 48.8% orthorhombic P 2 1 / ma, 49.1% tetragonal P 4 bm, and 2.1% tetragonal P 4 2 / mnm SnO 2, which is confirmed by the combination of X-ray diffraction and transmission electron microscopy. The ceramic features a pronounced core–shell structure with the shell region rich in stripe nanoscale domains of the P 2 1 / ma phase and the core region consisting of polar nanoregions deficient in the P 2 1 / ma phase, forming polar vortices. Consequently, the ceramic achieves an impressive recoverable energy storage density of 6.83 J cm –3 and an exceptional efficiency of 95.7% at a high breakdown strength of 750 kV cm –1, along with superior stability in frequency, temperature, and cycling. These results not only offer a viable approach for developing high-performance energy storage ceramics through the controlled formation of polar vortices but also offer the potential for direct electric-field control of polar vortices for high-speed data processing and storage.