Ultrahigh energy harvesting properties in temperature-insensitive eco-friendly high-performance KNN-based textured ceramics

Mechanical energy-driven wireless charging technology has recently gained increasing attention. In this work, high-performance potassium sodium niobate (KNN)-based textured ceramics and their potential application in energy harvesting devices are systematically investigated. A series of lead-free 0.99K(0.5)Na(0.5)Nb((1-x))Ta(x)O(3)-0.01Bi(Ni2/3Nb1/3)O-3 [KNNTa-BNN] piezoceramics were designed and prepared to search for good comprehensive properties. The comprehensive performance of KNN-based piezoelectric ceramics has reached a new level in T-Ta-9 (d(33) similar to 435 pC N-1, k(p) similar to 71%, T-c similar to 360 degrees C) via the synergy of the textured structure (f((00l)) > 94%) and multiphase coexistence (O-T) near room temperature. Based on the advanced in situ TEM and PFM analyses, it was found that the regular large-scale domains and corresponding poling patterns of the T-Ta-9 can be well maintained at relatively high temperatures (180-330 degrees C), resulting in excellent temperature stability. Hence, the d(33) value of T-Ta-9 can be maintained above 300 pC N-1 over a wide range from room temperature to 300 degrees C, which rarely happens in the previously reported KNN-based materials. More importantly, the piezoelectric circular diaphragm (PCD) vibration energy harvester based on the T-Ta-9 texture ceramic possesses high output voltage (U similar to 13 V) and output power (W similar to 3 mW), and can still maintain above 60% after being heated at 200 degrees C for 30 min. This work represents a significant advancement in the lead-free piezoelectric energy-harvesting field (especially for high-temperature applications) and can provide guidelines for future efforts in this direction.