Enhanced Curie temperature of BaTiO₃-based lead-free piezoceramics via localized compressive stress engineering

BaTiO₃ (BT)-based lead-free piezoceramics face limitations in high-temperature applications due to their low Curie temperature (T_C). Here, we propose a novel strategy to enhance T_C by generating localized compressive stress through a secondary Ba₂TiSi₂O₈ (BST) phase. In BT-xBST (0 mol% ≤ x ≤ 30 mol%) ceramics, T_C increases by 36 °C to 158 °C at x = 25 mol%, which one of the highest reported values for BT-based systems. GPA analysis of STEM images confirms compressive strain at BST-BT interfaces, significantly exceeding intragranular stress. Phase-field simulations quantitatively validate this mechanism, showing an 18 °C T_C increase under compressive stress, consistent with experiments. We attribute the enhancement to suppressed lattice expansion during the tetragonal-to-cubic transition, which raises the energy barrier for phase transformation. This stress engineering approach offers a generalizable route to design high-T_C piezoceramics beyond doping paradigms.