Enhancing Sensitivity of Flexible Piezoelectric Thin‐Film Acoustic Sensors via Buffer Layer Engineering for Insulation Health Monitoring of Power Cables

Abstract Partial discharge (PD) detection is critical for evaluating insulation degradation in high‐voltage power cables. Flexible piezoelectric acoustic sensors offer a compelling solution owing to their conformability to curved surfaces and strong immunity to electromagnetic interference. However, conventional piezoelectric thin films typically suffer from low sensitivity due to the intrinsic trade‐off between piezoelectric coefficient (d 33 ) and dielectric constant (ε r ). In this work, a TiO 2 buffer layer is introduced to engineer Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) thin films with significantly enhanced performance. The 266 nm TiO 2 buffer layer is prepared by the sol‐gel method. The TiO 2 layer reduces ε r from 650 to 150 at the frequency of ≈100 kHz, promotes refined grain, a self‐poled state, and strong (100) texture, and increases d 3 3 from 45 to 160 pm V −1 , resulting in an estimated ultrahigh piezoelectric voltage constant g 3 3 of 124 mV·m·N −1 . The fabricated flexible sensor exhibits a wide frequency response up to 600 kHz with an average sensitivity of 65 dB and peak sensitivity exceeding 70 dB. It captures high‐resolution acoustic signals of PD events in a 110 kV power cable, outperforming both unmodified PZT and commercial PVDF sensors. Long‐term and thermal stability evaluations confirm excellent durability. This study presents a robust strategy for tuning piezoelectric thin‐film properties via interface engineering and demonstrates the potential of TiO 2 ‐buffered PZT sensors for advanced acoustic sensing in power equipment insulation health monitoring applications.