| Phase Transition and Effect of Poling Temperature on Piezoelectricity of CaZrO3-Modified (K, Na)NbO3-Based Lead-Free Ceramics |
| Ke Wang |
| Tsinghua University |
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Keywords: Piezoelectric ceramics, Lead-free, Sodium potassium niobate
(K, Na)NbO3 (KNN)-based ceramics received incredible attention recently, due to its promising potential as next generation lead-free piezoceramics. The enhanced piezoelectric performance of KNN is recognized and related to the coexistence of polymorphic phases. Recently, we found that the phase constitution of CaZrO3-modified KNN ceramics is not only influenced by chemical doping, but also affected by intergranular stress. In addition, we also noticed that little attention has been paid to the optimization of poling conditions in KNN-based ceramics with a polymorphic phase transition, while electrical poling is indispensable for endowing isotropic ferroelectric polycrystals with a net macroscopic polarization and hence piezoelectricity. This study investigated the electrical properties of CaZrO3-modified KNN-based lead-free piezoceramics as a function of the poling temperature. Peak piezoelectric coefficient d33 of 352 7 pC/N and planar electromechanical coupling factor kp of 0.47 were obtained at the optimized poling temperature of 120 oC, which crosses the polymorphic phase transition regime. In-depth analysis of the asymmetric polarization hysteresis loops and bipolar strain curves uncovered striking analogy between electrical poling and unipolar cycling in the current system, which is attributed to a competition between domain reorientation and space charge accumulation.
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| Acknowledgements : This work was supported by National Nature Science Foundation of China (Grants No. 51332002, 51302144) and Tsinghua University Initiative Scientific Research Program. |
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