Giant piezoelectricity in potassium-sodium niobate lead-free ceramics

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 T _C∼217-304 C by optimizing the compositions. This giant d ₃₃ 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".