Giant Piezoelectricity in Potassium–Sodium Niobate Lead-Free Ceramics

TLDR

Lead‑free piezoelectric materials are sought for environmental and health reasons, and alkali niobate perovskites have been studied for over a decade, yet their peak piezoelectric coefficient has remained below 420 pC/N. The study reports an alkali niobate‑based lead‑free piezoceramic that achieves the highest recorded d33 of ~490 pC/N using conventional solid‑state synthesis. The exceptional d33 is attributed to a newly engineered rhombohedral–tetragonal phase boundary together with enhanced dielectric and ferroelectric properties. Optimized compositions deliver d33 values between 390 and 490 pC/N and Curie temperatures of 217–304 °C, pointing toward a viable route for practical lead‑free piezoelectrics.

Abstract

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"."