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

Dielectric energy-storage capacitors, known for their ultrafast 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, a TTBs relaxor ferroelectric ceramic based on the Gd0.03Ba0.47Sr0.485-1.5xSmxNb2O6 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-1 is reported. Notably, the energy storage performance of this ceramic shows remarkable stability against frequency, temperature, and cycling electric field. The introduction of Sm3+ doping is found to create weakly coupled polar nanoregions in the Gd0.03Ba0.47Sr0.485Nb2O6 ceramic. Structural characterizations reveal that the incommensurability parameter increases with higher Sm3+ content, indicative of a highly disordered A-site structure. Simultaneously, the breakdown strength is also enhanced by raising the conduction activation energy, widening the bandgap, 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. Obtaining high energy storage performance in tetragonal tungsten bronze dielectric ceramics is challenging, owing to the complexity of composition design and crystal structure. This study focuses on enhancing the recoverable energy density in Gd0.03Ba0.47Sr0.485-1.5xSmxNb2O6 by creating weakly coupled polar nanoregions. The resulting system exhibits ultrahigh energy storage, surpassing the majority of counterparts in ceramics with tetragonal tungsten bronze structures.image