Fine-grained barium stannate titanate ceramics obtained by current-controlled flash sintering for energy-storage applications

Current-controlled flash sintering provided an energy-efficient route to refine the microstructure of BaTi 0.85 Sn 0.15 O 3 ceramics. Full densification was achieved within minutes at 1200 ° C , yielding a fine-grained bimodal microstructure with mean grain sizes of ∼ 1 . 4 μ m and ∼ 4 . 3 μ m , in contrast to the coarse grains ( ∼ 90 μ m ) produced by conventional sintering after 3 h at 1350 ° C . Despite this substantial grain refinement, the flash-sintered ceramic preserved a recoverable energy density ( ∼ 46 mJ cm −3 ) and an efficiency ( ∼ 90%) comparable to those of the conventionally sintered specimen. Impedance spectroscopy revealed distinct electrical heterogeneity for each microstructure, yet these differences had no detrimental effect on the energy-storage performance; notably, the flash-sintered sample exhibited a higher electrical breakdown strength, highlighting the benefits of grain refinement. These findings demonstrate that current-controlled flash sintering enables the fabrication of dense, fine-grained ceramics without compromising functional properties, offering a promising route for microstructure engineering in lead-free dielectric energy-storage materials. • Current-controlled flash sintering enables rapid densification at reduced temperature. • Flash sintering produces a highly dense, fine-grained bimodal microstructure. • Grain refinement is achieved without degrading energy density or efficiency. • Flash-sintered ceramics exhibit enhanced electrical breakdown strength.