Ultrahigh Energy Storage in Tungsten Bronze Dielectric Ceramics Through a Weakly Coupled Relaxor Design.

Dielectric energy-storage capacitors, known for their ultra-fast discharge time and high-power density, find widespread applications in high-power pulse devices. However, ceramics featuring a tetragonal tungsten bronze structure (TTBs) have received limited attention due to their lower energy-storage capacity compared to perovskite counterparts. Herein, we report a TTBs relaxor ferroelectric ceramic based on the Gd 0.03 Ba 0.47 Sr 0.485-1.5 x Sm x Nb 2 O 6 composition, exhibiting an ultrahigh recoverable energy density of 9 J/cm 3 and an efficiency of 84% under an electric field of 660 kV/cm. Notably, the energy storage performance of this ceramic shows remarkable stability against frequency, temperature, and cycling electric field. The introduction of Sm 3+ doping was found to create weakly coupled polar nanoregions (PNRs) in the Gd 0.03 Ba 0.47 Sr 0.485 Nb 2 O 6 ceramic. Structural characterizations reveal that the incommensurability parameter increases with higher Sm 3+ content, indicative of a highly disordered A-site structure. Simultaneously, the breakdown strength is also enhanced by raising the conduction activation energy, widening the band gap, and reducing the electric field-induced strain. This work presents a significant improvement on the energy storage capabilities of TTBs-based capacitors, expanding the material choice for high-power pulse device applications. This article is protected by copyright. All rights reserved.