Strong piezoelectric anisotropy in CaBi₄Ti₄O₁₅ textured ceramics prepared by templated grain growth method

Bismuth layer-structured ferroelectrics (BLSF) show great potential as piezoelectric materials for high-temperature applications. In this study, c-axis/[001]-textured CaBi₄Ti₄O₁₅ (CBT) ceramic was synthesized through templated grain growth (TGG) method. A high Lotgering factor (f) of 96% was achieved in textured CBT ceramic using 20 wt% CBT homogeneous template. The piezoelectric coefficient d₃₃ has significantly increased from 7.8 pC/N for random ceramic to 24.3 pC/N for textured ceramic (poled perpendicular to the c-axis/[001] texture direction), representing an impressive 300% enhancement while maintaining an ultra-high Curie temperature (T_C) of 788°C. In addition, a low dielectric loss (tanδ = 0.4%) and relatively high resistivity (ρ = 1.1 × 10¹² Ω·cm) were achieved simultaneously at room temperature. The significant enhancement of d₃₃ in textured CBT ceramic origins from its strong piezoelectric anisotropy. The large d_33,T⊥ is due to the nature of polarization switching in CBT (the spontaneous polarization P_S of CBT is along a-axis direction, and the switching of P_S is restricted within the a–b plane). Furthermore, the variation of d_33,T⊥ remained below 10% across the temperature range of 25–700°C, highlighting the excellent thermal stability of the textured CBT ceramics. These findings suggest that textured CBT ceramic is a promising piezoelectric material for high-temperature sensor applications.