Piezoelectric hardening by redox reaction treatment in BaTiO₃-based piezoceramics

Mechanical loss critically limits the efficiency and stability of piezoelectric devices operated under resonance conditions. In this study, BaTiO₃-based piezoceramics doped with La were processed through a sequential reducing-oxidizing thermal treatment to induce piezoelectric hardening without altering the nominal composition. Structural analysis reveals that the oxidation treatment drives a transformation of the major phase symmetry and promotes the formation of a potential secondary phase, indicating a redistribution of doping element during redox processing. As a result, the treated piezoceramics exhibit an approximately 160% enhancement in mechanical quality factor Q _m accompanied by suppressed polarization and strain responses under large electric fields. These characteristics suggest effective inhibition of domain-wall motion induced by the redox-driven microstructural evolution. The proposed approach provides an alternative hardening strategy for BaTiO₃-based piezoceramics with potential for high-power and resonance-driven applications.