Manipulating temperature stability in KNN-based ceramics via defect design

The designed defect-engineering has been proved to be an effective way to promote properties in potassium sodium niobate (KNN)-based ceramics. Here, we focus on the introduction of Fe element into different sites of KNN-based ceramics to form defects and optimize properties. Two types of defect dipoles can be formed, Fe-(A) over dot - V'(A )for A-site and Fe ''(Nb)-V-(O) over dot for B-site. Compared with the defect dipoles of A-site, the defect dipoles of B-site are sensitive to both electric field and temperature. So that, the B-site defect dipoles switch easily under the thermo-electric treatment, and share the same behavior with spontaneous polarization after removing the electric field, which compensates the remnant polarization. In addition, the domain miniaturizes as the Fe ions doping. Both of the defect dipole behavior and nanodomain lead to the preferable temperature stability: remnant polarization (P-r) and unipolar strain (S) of the B-site engineered ceramics vary less than 10% and 15% in the temperature range of 20-140 degrees C. We hope that the strategy of designed defect dipoles is helpful for improving electrical properties and further promoting the development of KNN-based ceramics. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The designed defect-engineering is proven to be an effective way to enhance properties in KNN-based ceramics. Introducing Fe element into different sites of KNN-based ceramics can form two types of defect dipoles, with B-site defect dipoles being more sensitive to electric field and temperature. The behavior of defect dipoles and nanodomain lead to preferable temperature stability in B-site engineered ceramics.