Grain-size dependence of flexoelectric response in giant dielectric CaCu3Ti4O12

Grain structure plays a crucial role in the dielectric response of CaCu3Ti4O12 (CCTO) ceramics, attributed to the internal barrier layer capacitor mechanism. Despite the close relation between flexoelectricity and dielectricity, how grain structure affects CCTO flexoelectric response remains unexplored. Here, CCTO ceramics with different grain sizes of 0.8–15 μm were prepared by controlling sintering temperatures. It shows that increased grain size tends to enhance both dielectric and flexoelectric responses, with the dielectric constant varying from ∼1300 to ∼16 700 and the apparent flexoelectric coefficient μ12 varying from 6.82 to 11.73 μC/m, respectively. This indicates that the flexoelectric and dielectric responses in CCTO ceramics are homologous in origin. Impedance measurements further reveal that the Schottky barrier height decreases with increasing grain size, which contributes to the nonlinear evolution of responses. Our study extends understanding of the grain-size effect in flexoelectric ceramics and offers guidance for flexoelectric enhancement via grain-size modulation.