The microstructure, phase transition, and electrical properties of lead-free K x Na 1Àx NbO 3 (x = 0.46 to 0.51, abbreviated as KNN) piezoceramics prepared by a conventional solid-state reaction method were investigated with an emphasis on the influence of the K/Na ratio. Scanning electron microscopy (SEM) images showed that the grain growth was slightly improved by increasing x. However, all ceramic samples possessed high densifications with fine grains from several hundred nanometers to several micrometers. X-ray diffraction (XRD) results showed that a discontinuous change of lattice parameters appeared between x = 0.49 and 0.50, which suggested a typical morphotropic phase boundary (MPB) separating two different orthorhombic phases O I and O II . The sample with composition x = 0.49 had the peak values of the piezoelectric constant d 33 of 146 pC/N and the planar electromechanical coupling coefficient k p of 43%. These results indicated that improving the piezoelectric properties in KNN ceramics could be achieved by optimizing the K/Na ratio.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.