Epitaxial High-Entropy Relaxor Ferroelectric Films for Flexible Piezoelectric Sensors and MEMS

Flexible high-entropy relaxor ferroelectrics offer a promising route to overcome the long-standing challenges between mechanical flexibility, thermal stability, and electromechanical performance in piezoelectric applications. In this study, we design epitaxial Pb(Mg0.15Nb0.3Ti0.05Hf0.25Zr0.25)O3 (PMNTHZO) films and integrate them onto both silicon and flexible muscovite (mica) substrates. These films exhibit excellent epitaxial crystallinity, a significantly enhanced breakdown electric field (> 4 MV cm−1 on silicon), and superior thermal stability through high-entropy engineering. Macroscopic piezoelectric measurements show strain-dependent current outputs and high cycling reliability, while nanoscale PFM reveals large effective d33 values (≈100 pm V−1). PMNTHZO maintains stable polarization switching above 250 ◦C and demonstrates remarkable mechanical durability, with a bending radius as small as 3.5 mm and over 10,000 cycles of continuous deformation. Thickness-dependent and fabricated micro island structures further confirm the minimal influence of substrate clamping on piezoresponse using mica substrate. These results establish PMNTHZO on mica and Si as a thermally stable, mechanically flexible, high-entropy piezoelectric material, enabling next-generation flexible sensors.