Cross-layer structural coupling in CaBi2Nb2O9 ceramics via Ce3+/La3+ modification

Research on Aurivillius ceramics mainly focuses on perovskite-like slabs, whereas fluorite-like (Bi 2 O 2 ) 2+ layers are often regarded as passive. Here, Ce 3+ /La 3+ -modified CaBi 2 Nb 2 O 9 -based ceramics were designed to clarify how engineering the (Bi 2 O 2 ) 2+ layers affects cross-layer structural coupling and electromechanical response. Ce 3+ /La 3+ incorporation weakens orthorhombic distortion and induces tetragonal-like evolution while maintaining the Aurivillius framework. Raman and XPS results further demonstrate that this modification simultaneously alters the local Bi–O environment, A-site Ca 2+ coordination, NbO 6 octahedral distortion, and defect chemistry, confirming pronounced coupling between the fluorite-like layers and perovskite slabs. In addition, Ce 3+ /La 3+ incorporation suppresses Bi volatilization, improves densification and optimizes the domain morphology. As a result, the ceramic with x  = 0.05 exhibits an enhanced piezoelectric coefficient d 33 of 15.9 pC/N while retaining a high Curie temperature of 921 °C. This work demonstrates that targeted engineering of the (Bi 2 O 2 ) 2+ layers is an effective route for regulating cross-layer coupling and improving the performance of high-temperature Aurivillius piezoceramics.