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Flexoelectricity yields electric polarization through graded strains and exists in various kinds of solid dielectrics but usually with a weak coupling response. In this letter, several Bi-doped Pb(Mg2/3Nb1/3)O3-xPbTiO3 (PMN-xPT) ferroelectric ceramics were prepared and the interplay of their piezoelectricity and flexoelectricity was systematically investigated. The largest flexoelectric response (∼300 μC/m) was 30 times larger than that of pure PMN-PT and was observed in the Bi-doped PMN-32PT, where the after poling piezoelectric coefficients were also the largest (990 pC/N) among all the compositions. This suggests that the apparent flexoelectricity in ferroelectrics is highly related to the bulk piezoelectricity. Therefore, introducing a local structural heterogeneity is considered as a feasible approach to achieve an ultrahigh piezoelectric response while also providing an ultrahigh flexoelectricity. [ABSTRACT FROM AUTHOR]

Traditional piezoelectric adaptive lenses (ALENS) are fabricated by piezoceramics with transparent liquids as the filling media. However, it is challenging to achieve high focal sensitivity and long-time robustness because of the low piezoelectricity of ceramics as well as the evaporation and leakage of the liquids. To overcome the above-mentioned issues, we design a piezoelectric lens based on a radial extension-arching mode by using polydimethylsiloxane films and Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIMNT) relaxor ferroelectric single crystals to replace the transparent liquids and Pb(Zr, Ti)O3 (PZT) ceramics, respectively. Due to the ultrahigh piezoelectric properties (d33 ∼ 1500 pC N−1 and d31 ∼ 730 pC N−1) of the PIMNT crystals and the optimized radial extension-arching structure, an ultrahigh focal sensitivity (8.5 cm V−1 and a fast response time (∼102μs) is achieved, outperforming conventional ALENS based on piezoceramic actuators (∼103 μs and ∼10−1 cm V−1) and dielectric elastomer actuators (∼105 μs and ∼10−2 cm V−1). The largest output displacement of our designed ALENS is up to 53.6 μm at 4.2 kHz under 80 Vpp, and its focus is in the range of 57.44 cm to ∞. Furthermore, its performance remains unchanged after 4 × 107 vibration cycles, indicating its long-time robustness. This work sheds light on the design of advanced adaptive optical systems, where an ultrahigh focal sensitivity and a fast response are required. [ABSTRACT FROM AUTHOR]