Improved piezoelectricity in ternary potassium-sodium niobate lead-free ceramics with large strain

摘要

Although potassium-sodium niobate (KNN)-based ceramics with good piezoelectric performance have been obtained by a phase engineering strategy, a low electric field-induced strain (<0.2%) even when applying large electric fields is observed in the ceramics prepared by normal sintering, which hardly satisfies practical application demands. Here, a ternary lead-free material system of (0.965 - x)K0.5Na0.5Nb0.975Sb0.25O3-0.035Bi(0.5)Na(0.5)ZrO(3)-xBiFeO(3) (KNNS-BNZ-xBF, 0 <= x <= 0.008) ceramics with excellent overall performance has been designed, aiming to achieve balanced development between piezoelectric and strain properties. A systematic study of the phase structure, electric properties and temperature stability is carried out on the ceramics, and the optimal electric properties (e.g., d(33) approximate to 511 pC N-1, S-uni approximate to 0.202%, d(33)* approximate to 505 pm V-1, and T-c approximate to 269 degrees C) are obtained at x = 0.007 owing to the large tetragonality and R-T phase structure with low polarization anisotropy as well as weak energy barriers. Moreover, a new approach used to evaluate coercivity (E-c) qualitatively provides more choices to identify E-c in ferroelectrics. We believe that it may promote the application of lead-free piezoelectric materials.