MnO₂ doping induced structural tuning drives superior piezoelectric response in CaBi₄Ti₄O₁₅-based ceramics

Composition optimization and domain engineering modulation with diverse elements and structural tuning are favorable pathways that can be implemented to increase piezoelectric properties. Here, CaBi₄Ti_3.89(W_1/2Co_1/2)_0.11O₁₅+x wt%MnO₂ (CBTWC–xMn, x = 0–0.25) ceramics with superior piezoelectric responses were prepared via a solid-state sintering method. The mechanism of the high piezoresponse was examined by integrating visual crystal structure analysis with piezoresponse force microscopy, revealing that the introduction of MnO₂ led to greater distortion of the [TiO₆] octahedron and a more oriented domain structure, both of which are critical factors contributing to the enhanced piezoelectric response. The optimized CBTWC–0.1Mn ceramics achieved an ultrahigh piezoelectric constant (d₃₃ = 27.3 pC/N), which was 50% greater than that of the pure CBTWC ceramics. Furthermore, the CBTWC–0.1Mn ceramics exhibited better ferroelectric properties, a high Curie temperature (T_C = 754.7 °C), low dielectric loss (tanδ = 6.7% at 500 °C), and excellent thermal stability, and their d₃₃ (26.3 pC/N) maintained over 95% of its initial value after annealing at 500 °C. This work provides a feasible strategy for improving the properties of bismuth layer-structured piezoelectric ceramics, which has important prospects for the application of high-temperature piezoelectric devices.