Following increased environmental concerns on the toxicity of lead, the discovery of ultrahigh piezoelectricity in lead-free piezoelectric materials is critical for the substitution of commercial lead zirconate titanate (PZT) ceramics in numerous electronics. In this work, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoelectric materials by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity This strategic materials design approach is based on first-principles calculations combined with Landau phenomenological theory and phase field simulations. Sustainable Stannum-doped BaTiO 3 lead-free ferroelectric ceramics is prepared to validate our proposed mechanism, and a giant piezoelectric coefficient d 33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. The mechanism and paradigm of the excellent piezoelectricity achieved here provides a feasible solution for replacing lead based piezoelectrics by lead-free counterparts.

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New piezoelectric ceramics, 0.71BiFe 1Àx (Ni 1/2 Ti 1/2 ) x O 3 À0.29 BaTiO 3 +0.6 wt% MnO 2 [BFNTx-BT] (x = 0-0.09), were fabricated using conventional mixed-oxide method. It was found that the introduction of BNT into BF-BT system caused insignificant change in crystal structure, which is a single-phase perovskite structure. However, an obvious variation in microstructure took place. The ceramics with composition of x = 0.03 showed enhanced piezoelectric, electromechanical, and ferroelectric properties with piezoelectric constant d 33 = 156 pC/N, planar electromechanical coupling factors k p = 0.308, remnant polarization P r = 22.5 lC/cm 2 , and coercive field E c = 28.2 kV/cm, with a high Curie temperature T c = 431°C, respectively. The combination of good piezoelectric properties and high T c makes these ceramics suitable for elevated temperature piezoelectric devices.S. Zhang-contributing editor Manuscript No. 31355.

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