Enhanced energy storage performance in SBNN-based tungsten bronze ceramics through co-substitution strategy in A/B sites

Tungsten bronze lead-free (Sr0.7Ba0.3)2_xBixNaNb5_xTixO15 ceramics were fabricated via the traditional solid-state reaction method. The effects of co-doping Bi3+/Ti4+ in A/B sites on the structures, relaxor characteris-tics, and energy storage performance were studied. All ceramics exhibited a pure TTB structure. The phase structure for all ceramics evolved from P4bm to P4/mbm symmetry with increasing content of the co-doping ions. The introduction of Bi3+ and Ti4+, which have different valence states, may have caused random occupation of ions in both A and B sites and increased the distorting degree of BO6 octahedra, leading to the merger of two dielectric anomalous peaks and dielectric relaxation. Finally, a relatively good energy storage density (1.8 J/cm3) and an ultrahigh efficiency (87 %) were achieved under an applied electric field of 210 kV/cm for ceramics with x = 0.20. Moreover, the energy storage densities and efficiencies were stable over a large number of cycles (105 times). This demonstrates the potential of these ceramics for application as dielectric capacitors.