Compositional heterogeneity enhancing the flexoelectric response of BaTiO3 -based ceramics

Flexoelectric effect possesses potential applications in electromechanical conversion, and the flexoelectric coefficient of ferroelectrics is greatly larger than that of ordinary dielectrics . Among the ferroelectrics, BaTiO 3 (BT) ceramics are lead-free materials, also receive a high flexoelectric response. However, it is still inferior to the piezoelectric response of lead-based piezoelectric materials . Herein, we inhomogeneously added x wt. % ZrO 2 into BT ceramics ( x wt. % ZrO 2 /BT ceramics, and x  = 0.05, 0.5, 1, 2) to enhance the flexoelectric response of BaTiO 3 -based ceramics. The largest effective flexoelectric coefficients ( μ ρ ) of ∼800 μC/m at room temperature (RT) and ∼1500 μC/m near Curie temperature ( T C  ∼ 127 °C) were obtained in 0.5 wt % ZrO 2 /BT ceramics, which is ∼6.7 times and ∼3.9 times larger than that of the as-prepared BT ceramics at RT and near T C (∼131.7 °C here) respectively. Although T C of the 0.5 wt % ZrO 2 /BT ceramics decreases compared with that of BT ceramics, its higher μ ρ than that of the as-prepared BT ceramics maintains a wide temperature range, extending to 160 °C. The enhancement of the μ ρ of the 0.5 wt % ZrO 2 /BT ceramics is largely attributed to the compositional heterogeneity between grain boundaries gathered with irregular paraelectric and orthorhombic Ba(Zr, Ti)O 3 , and grains which are tetragonal BaTiO 3 . The compositional heterogeneity is easily shaped into a strain gradient (namely a flexoelectric polarization), which plays a promoting effect on the flexoelectric coefficients.