Tough and high-temperature stable nacre-like Bi4Ti3O12-based piezoceramics
Bi4Ti3O12-based ceramics are promising candidates for high-temperature piezoelectric devices owing to their high Curie temperature (> 600 °C). However, their low piezoelectric constants and poor mechanical reliability hinder their use in some engineering applications. Here, we fabricate nacre-like <00l>-textured (f_00l > 94%) Bi3.96Ce0.04Ti2.965W0.0175Nb0.0175O12 (NL-BCWNT) ceramics via a scalable magnetic-assisted slip casting (MASC) self-assembly process. In addition to crystallographic texture, the final material presents a brick-and-mortar microstructure with micro-sized grains with a median aspect ratio of 15. NL-BCWNT exhibits a high fracture toughness for piezoceramics, with both $K_{IC}$ and $K_J$ reaching 2.2 $\pm$ 0.4 $MPa \cdot m^{0.5}$ and 4.2 $\pm$ 0.4 $MPa \cdot m^{0.5}$, respectively. The toughening originates from deflection and stable crack propagation within the nacre-like structure. The $d_{33}$ is 30 $\pm$ 3 $pC/N$ with a Curie temperature of 661$°C$, and $d_{33}^*$ reaches 46 $\pm$ 3 $pm/V$ at 160 $° C$ with less remanent strain than random BCWNT. The improvements are attributed to aligned domain along spontaneous polarization direction with better mobility. NL-BCWNT exhibited excellent ferroelectricity fatigue resistance with higher than 106 cycles without degradation. Furthermore, similar improvements are observed in pure BiT, suggesting the general applicability of this strategy to other BiT-based systems. The nacre-like architecture thus provides a promising addition to the design toolbox for high-performance electromechanical materials.