Piezoelectric and ferroelectric properties of Cu-doped K<sub>0.5</sub>Na<sub>0.5</sub>NbO<sub>3</sub> lead-free ceramics
Lin, Dunmin; Kwok, K W; Chan, H L W; Lin, Dunmin; Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Kowloon, Hong Kong, People's Republic of China; College of Chemistry and Materials Science, Sichuan Normal University, Chengdu 610066, People's Republic of China; Kwok, K W; Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Kowloon, Hong Kong, People's Republic of China; Chan, H L W; Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Kowloon, Hong Kong, People's Republic of China
Журнал:
Journal of Physics D: Applied Physics
Дата:
2008-02-21
Аннотация:
CuO-doped K<sub>0.5</sub>Na<sub>0.5</sub>NbO<sub>3</sub> (K<sub>0.5</sub>Na<sub>0.5</sub>NbO<sub>3</sub> + x mol% CuO) lead-free ceramics have been prepared by an ordinary sintering technique. The results of x-ray diffraction patterns show that all the ceramics possess a pure pervoskite structure with orthorhombic symmetry. Based on the symmetry-conforming principle of point defects, defect dipoles are formed by the acceptor dopant ions Cu<sup>2+</sup> and O<sup>2−</sup> vacancies along the polarization direction and remain in the original orientation, providing a restoring force to reverse the switched polarization, which results in double polarization-electric hysteresis loops for the ceramics with x ≥ 0.50 at 100 Hz. That is, the ferroelectric dipoles are back to their original orientation on the removal of electric field due to the strong restoring force generated by defect dipoles. As a result, the ceramics (x ≥ 0.5) become considerably ‘hardened’ and possess an extraordinarily high Q<sub>m</sub> (825–2523) and simultaneously the other piezoelectric properties remain reasonably good (k<sub>p</sub> = 39%, k<sub>t</sub> = 47% and d<sub>33</sub> = 82 pC N<sup>−1</sup>).
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