Breaking the Transparency-Piezoelectricity Trade-Off in Lead-Free Ceramics via Tailoring Local Polarization...

Despite the widespread applications of transparent ceramics and piezoelectric ceramics in their respective fields, the intrinsic incompatibility in the microstructural characteristics remains the core bottleneck restricting breakthroughs in the performance of lead-free transparent piezoelectric ceramics. Here, to achieve simultaneous enhancement of optical transmittance and piezoelectricity, a tetragonal-pseudocubic phase boundary was constructed in the potassium-sodium niobate (KNN)-based transparent ceramics, successfully modulating local polarization disorder within an ordered framework. Through atomic-scale analysis, the mechanism underlying the synergistic enhancement of macroscopic lattice symmetry and microscopic polarization response was elucidated. As a result, the optimal KNN-based ceramics exhibit state-of-the-art optical transmittance (72% @ 780 nm) and a large piezoelectric coefficient (157 pC/N), surpassing those of other lead-free ferroelectric ceramics. Furthermore, leveraging its transparency and pressure sensing capabilities, we proposed a visual force feedback prototype tailored for medical endoscopic applications, offering a critical reference for the exploration of next-generation intelligent sensing devices.