Dielectric and electrical energy storage properties of a series of high-entropy tetragonal tungsten bronze ceramics

Including Na+, Ag+, Bi3+, and K+ at A sites and selecting two cations from Mg2+, Ca2+, Sr2+, and Ba2+, a new class of high-entropy filled tungsten bronze oxides, Na0.5Ag0.5Bi0.5K0.5(XY)0.5Nb5O15 (XY = MgCa, MgSr, MgBa, CaSr, CaBa, SrBa) has been synthesized by solid-state reaction method. The A-sites of these oxides are occupied by six different elements in equimolar ratio. The structure, dielectric, and electrical energy storage properties of the ceramics were studied comprehensively from the views of cationic radius, polarizability, and configurational entropy. Particularly, Na0.5Ag0.5Bi0.5K0.5(CaBa)0.5Nb5O15 gets a recoverable energy storage density of 3.11 J/ cm3 at 200 kV/cm, which is higher than representative dielectric ceramics at this moderate electric field. Besides, Na0.5Ag0.5Bi0.5K0.5(MgBa)0.5Nb5O15 gets a high efficiency of 89 % with a recoverable energy storage density of 2.5 J/cm3 at 225 kV/cm. These properties indicate that the new class of high-entropy-filled TTB ceramics has potential applications in electrical energy storage devices.