Grain-boundary engineering by spark plasma texturing to enhance dielectric breakdown strength in barium strontium titanate ceramics

Dielectric breakdown strength ( E bd ) limits the reliability and energy density of functional oxide ceramics in high-field applications. Here, we demonstrate that Spark Plasma Texturing (SPT) dramatically enhances E bd in Ba 0.6 Sr 0.4 TiO 3 (BST) ceramics. Dynamic thermo-mechanical coupling during SPT produces a near-fully dense, highly homogeneous microstructure with ultra-fine grains (0.44 μm), resulting in E bd of up to 515 kV·cm −1 , which is more than twice higher than 200 kV·cm −1 for conventionally sintered ceramics and one third higher than 384 kV·cm −1 for ceramics prepared by standard SPS. This enhancement is of extrinsic origin and grain-boundary-controlled: impedance spectroscopy reveals elevated activation energies and resistive grain-boundary barriers that suppress long-range charge migration, while the intrinsic electronic structure with bandgap ~ 3.0 eV remains unchanged. SPT is thus established as an effective route for grain-boundary engineering in functional oxides, enabling high-reliability energy storage and tunable radio-frequency devices. • Major dielectric strength improvement: Spark Plasma Texturing (SPT) more than doubles the dielectric breakdown strength of BST ceramics, reaching 515 kV·cm −1 , outperforming conventional sintering and standard SPS. • Controlled grain-boundary engineering: SPT enables an edge-free thermo-mechanical process that produces a near-fully dense, highly uniform microstructure with ultrafine grains (~0.44 μm ) . • Improved high-field reliability: Resistive grain-boundary barriers suppress charge migration, enhancing performance for energy storage and tunable RF applications . • Scalable lead-free advancement: Grain refinement through SPT governs breakdown behaviour in lead-free BST , enabling higher energy density and wider tunability without altering intrinsic electronic properties.