Environment protection and human health concern is the driving force to eliminate the lead from commercial piezoelectric materials. In 2004, Saito et al. [ Saito et al., Nature , 2004 , 432 , 84 . ] developed an alkali niobate-based perovskite solid solution with a peak piezoelectric constant d33 of 416 pC/N when prepared in the textured polycrystalline form, intriguing the enthusiasm of developing high-performance lead-free piezoceramics. Although much attention has been paid on the alkali niobate-based system in the past ten years, no significant breakthrough in its d33 has yet been attained. Here, we report an alkali niobate-based lead-free piezoceramic with the largest d33 of ∼490 pC/N ever reported so far using conventional solid-state method. In addition, this material system also exhibits excellent integrated performance with d33∼390-490 pC/N and TC∼217-304 °C by optimizing the compositions. This giant d33 of the alkali niobate-based lead-free piezoceramics is ascribed to not only the construction of a new rhombohedral-tetragonal phase boundary but also enhanced dielectric and ferroelectric properties. Our finding may pave the way for "lead-free at last".

The experimental characteristics of polarization fatigue in thin-film, bulk ceramic, and single-crystalline ferroelectrics have been reviewed in detail. Various scenarios and models proposed for fatigue in ferroelectric materials during the past few decades have been discussed, together with our own model developed very recently [Phys. Rev. Lett. 97, 177601 (2006); Phys. Rev. B 75, 244104 (2007)]. Interpretations for the experimental data reviewed in this paper but untreated in our previous work [Phys. Rev. B 75, 244104 (2007)] as well as the methods of improving the fatigue endurance in ferroelectrics are given based on this model. Finally, the results on polarization fatigue in some special classes of ferroelectrics such as multiferroics (e.g., BiFeO3-based materials), ferroelectric polymers, and antiferroelectric thin films and ceramics are discussed and accounted for in light of our model.

Ultrahigh energy storage density of 52.4 J cm with optimistic efficiency of 72.3% is achieved by interface engineering of epitaxial lead-free oxide multilayers at room temperature. Moreover, the excellent thermal stability of the performances provides solid basis for widespread applications of the thin film systems in modern electronic and power modules in harsh working environments.

High-performance lead-free piezoelectrics (d33 > 400 pC/N) based on 0.96(K0.5Na0.5)0.95Li0.05Nb1-xSbxO3-0.04BaZrO3 with the rhombohedral-tetragonal (R-T) phase boundary have been designed and prepared. The R-T phase boundary lies the composition range of 0.04 ≤ x ≤ 0.07, and the dielectric and piezoelectric properties of the ceramics with the compositions near the phase boundary are significantly enhanced. In addition, the ceramic with x = 0.07 has a giant d33 of ~425 pC/N, which is comparable to that (~416 pC/N) of textured KNN-based ceramics (Saito, Y.; Takao, H.; Tani, T.; Nonoyama, T.; Takatori, K.; Homma, T.; Nagaya, T.; Nakamura, M. Nature 2004, 432, 84). The underlying physical mechanisms for enhanced piezoelectric properties are addressed. We believe that the material system is the most promising lead-free piezoelectric candidates for the practical applications.

Piezocatalysis,converting mechanical vibration into chemical energy,h as emerged as ap romising candidate for water-splitting technology.H owever,t he efficiency of the hydrogen production is quite limited. We herein report welldefined 10 nm BaTiO 3 nanoparticles (NPs) characterized by al arge electro-mechanical coefficient which induces ah igh piezoelectric effect. Atomic-resolution high angle annular dark field scanning transmission electron microscopy(HAADF-STEM) and scanning probe microscopy(SPM) suggests that piezoelectric BaTiO 3 NPs displayac oexistence of multiple phases with lowe nergy barriers and polarization anisotropy which results in ahigh electro-mechanical coefficient. Landau free energy modeling also confirms that the greatly reduced polarization anisotropyf acilitates polarization rotation. Employing the high piezoelectric properties of BaTiO 3 NPs,w e demonstrate an overall water-splitting process with the highest hydrogen production efficiency hitherto reported, with aH 2 production rate of 655 mmol g À1 h À1 ,whichcould rival excellent photocatalysis system. This study highlights the potential of piezoelectric catalysis for overall water splitting.