Manipulating temperature stability in KNN-based ceramics via defect design.

Different types of defect dipoles form, F e A.. − V A ′ for A-site and F e N b ″ − V O.. for B-site according to the dopant sites [Fig. 1(a)]. Both of the temperature stable miniatured domain [Fig. 1(b)] and active defect dipole F e N b ″ − V O.. [Fig. 1(c)] in the B-site 0.05 leads to the preferable temperature stability, that is, the remnant polarization (P r) and unipolar strain (S) vary less than 10% and 15% in the temperature range of 20-140 °C, which is superior to other systems [Fig. 1(d)]. We believe that the strategy of designed defect dipoles is helpful for improving electrical properties and further promoting the development of KNN-based ceramics. [Display omitted] 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, F e A.. − V A ′ for A-site and F e N b ″ − V O.. 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 °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. [ABSTRACT FROM AUTHOR]