Decoding the Role of Diffused Multiphase Coexistence in Potassium Sodium Niobate-Based Ceramics with Nanodomains for Enhanced Piezoelectric Devices

Although multiphase coexistence endows potassium sodium niobate (KNN)-based ceramics with enhanced piezoelectric properties and promising potential in electronic devices, the physical mechanisms are still left way far behind. In this paper, (1–x)K0.48Na0.52Nb0.95Sb0.05O3–x(Bi0.5Ag0.5)(Zr0.9Hf0.1)O3 ceramics were selected as an example to probe the physical mechanisms. By tailoring the x value, a diffused rhombohedral–orthorhombic–tetragonal (R–O–T) coexistence was obtained at x = 0.04, affording a large piezoelectric coefficient d33 of 510 pC/N and a high Curie temperature Tc of 219 °C. The piezoelectricity enhancement mainly originated from the enhanced dielectric response and abundant submicron striped domains (50–100 nm) consisting of hierarchic nanodomains (10–15 nm). Importantly, although the diffused R–O–T multiphase coexistence exhibited facilitated domain switching, it was also bothered by reduced effectively reoriented domains and increased back-switching of already reoriented domains. Therefore, understanding the related physical mechanism is helpful to the further design of high-performance KNN-based ceramics used for electronic devices.