Broad temperature plateau of high piezoelectric constant via composite MPB engineering in BNT-based ceramics

To meet the demands of aerospace and other fields for stable performance of piezoelectric ceramics in high-temperature environments, ensuring consistent performance across a wide temperature range has become a critical issue to address. This study developed composite ceramics by combining BNT-7BT and BNT-20BKT, both exhibiting morphotropic phase boundary (MPB) characteristics and similar piezoelectric coefficients. The multiphase coexistence in these ceramics preserved high piezoelectric performance ( d 33 ∼162pC/N) while minimizing the adverse effects of quenching on d 33 . The compositional gradient induced by inhomogeneous diffusion pinned domain walls, thereby suppressing domain disordering at high temperatures and effectively restricting the fluctuation of d 33 to ≤11.5% across the operational temperature range until depolarization. The quenching-induced thermal gradient generated a built-in electric field (E b ) that effectively compensated the depolarization field (E d ), enabling the composite ceramics to achieve an ultrahigh depolarization temperature ( T d ) of 195 °C. This work successfully integrates high d 33 , T d , and thermal stability in BNT-based ceramics, offering a promising solution for high-temperature applications.