부산대학교 도서관

The pre-annealed sintering method was attempted to obtain (K,Na)NbO3 ceramics with a homogeneous microstructurewithout abnormal grain growth for multi-layered piezoelectric energy harvester application. The CuO and Na2CO3-doped(K,Na)NbO3 ceramics by normal sintering at temperatures above 900 oC displayed excellent piezoelectric properties butshowed an inhomogeneous microstructure due to an abnormal grain growth. Meanwhile, the ceramics sintered attemperatures of 880-900 oC showed a homogeneous microstructure and poor piezoelectric properties. The grain growth wasinfluenced by a grain shape in a normal sintering. The sample that were sintered at temperatures of 880-900 oC with roundedgedgrains showed a normal grain growth, whereas samples sintered at temperatures above 900 oC with faceted grainsexhibited abnormal grain growth. The specimen sintered at 940 oC for 3 hours after pre-annealing at 900 oC for 6 hoursshowed a homogeneous microstructure and excellent piezoelectric properties which are suitable for multi-layered piezoelectricenergy harvesting applications. An electromechanical coupling factor (kp), piezoelectric strain constant (d33), and mechanicalquality factor (Qm) were 0.431, 143 pC/N, and 737, respectively and the figure of merits for a piezoelectric energy harvesterin the resonance (kp2∙Qm) and off-resonance conditions (d33∙g33) were 137 and 7.5 pm2/N in the sample prepared by a preannealedsintering.