Flexoelectric effect in ceramic lead zirconate titanate

Mechanical strain gradient generated electric polarization or flexoelectric effect was investigated in unpoled lead zirconate titanate (PZT) ceramics in the ferroelectric state by using a cantilevered beam based approach. Flexoelectric coefficient ${\mu }_{12}$ at room temperature was measured to be $1.4\mu \mathrm{C}∕\mathrm{m}$ in the PZT ceramic at small level of strain gradient. Temperature-dependent experimental investigations clearly showed that high dielectric permittivity in the ferroelectrics enhanced flexoelectric polarization: essentially a linear relation was found to exist between ${\mu }_{12}$ and dielectric susceptibility $\chi$ at lower permittivity level (2100–2800), while ${\mu }_{12}$ versus $\chi$ curve started to deviate from the straight line at the $\chi \sim 2800$ and nonlinear enhancement of ${\mu }_{12}$ with $\chi$ was observed, with ${\mu }_{12}$ value reaching 9.5 at $\chi \sim 11000$ . The nonlinearity in the flexoelectric effect was associated with domain-related processes. It is suggested that flexoelectric effect can have a significant impact on epitaxial ferroelectric thin films and mesoscopic structures.