Ultrahigh electromechanical response in (K,Na)NbO₃-based lead-free textured piezoceramics

The progress of next-generation electromechanical devices is substantially reliant upon achieving high electromechanical coupling performance in piezoelectric materials. Here, a local stress regulation strategy is introduced to significantly enhance the overall electromechanical response of lead-free piezoceramics. A remarkable large piezoelectric coefficient (d₃₃) of ∼800 pC N⁻¹ and longitudinal electromechanical coupling factor (k₃₃) of 88% are obtained in (K,Na)NbO₃ (KNN)-based textured piezoceramics. From both experimental examinations and theoretical simulation, including phase-field analyses, it is found that the improved piezoelectric performance primarily stems from the stress-induced elastic field aligned with the preferred crystallographic orientation, which constrains the domain size, resulting in nanoscale short-range ordered domain structures. Such structures facilitate the flexible rotation of electric dipoles within coexisting phases due to flattened free energy distribution, thereby leading to the exceptionally large piezoelectric response. This understanding provides valuable guidance for the design of novel lead-free piezoceramics with excellent piezoelectric performance.