Perovskite-Layered Ultra-High-Temperature Piezoelectric Ceramics: Research Progress in Structural Origins, Compositional Design, and Fabrication Processes

ABSTRACT: Perovskite-layer structured (PLS) piezoelectric ceramics, featuring ultrahigh Curie temperatures (T_C), high electrical resistivity (ρ), and excellent thermal stability, are promising for sensing above 600 °C. However, poor densifiability, difficult poling, and low piezoelectric coefficients (d₃₃) still limit their practical applications. Focusing mainly on advances since 2018, this review critically evaluates recent progress in the structural understanding, compositional design, and processing of PLS ceramics. Improved control of lattice distortion, polarization switching, densification, and grain orientation has increased d₃₃ to approximately 3–4 pC/N in Sr₂Nb₂O₇-based ceramics and approximately 9 pC/N in La₂Ti₂O₇-based systems. Nevertheless, in situ high-temperature piezoelectric data, long-term stability studies, and device-level validation remain limited. Further progress requires synergistic composition-processing optimization and standardized high-temperature evaluation to advance PLS ceramics toward practical ultrahigh-temperature sensing applications.