报告人: DaeYong JEONG
报告题目：High energy density of lead-free ferroelectric thick films through mechanically induced quasi-relaxor behavior
DaeYong Jeong is a professor in the Department of Materials Science & Engineering at Inha University, Korea. He received the B.S. in 1994 and M.S. degrees in 1996 from Seoul National University and the Ph.D. degree from Pennsylvania State University in 2004. He worked for the TRS in USA and Tohoku University in Japan as a postdoc researcher. He was a senior scientist in Korea Institute of Science and Technology (KIST) before moving to Myongji University in Korea. Since 2011, he is a professor at Inha University. His research is focusing on ferroelectric materials and aero-sol deposition process. For the researches on ferroelectrics, his group is working on nano-grained ferroelectric to explore the fundamental phenomena from nano-size effects. In addition, for device applications, he is studying on energy harvesting using ferroelectric single crystals, high energy density capacitor, electrocaloric devices, and sensor & actuator.
Ferroelectric ceramic films with high energy density are promising for miniature power electronic device applications. For superior energy storage performance of capacitors, large recoverable energy density along with high efficiency, high power density, fast charge/discharge rate, and good thermal/fatigue stability of the ferroelectric ceramic are desired. We fabricated the highly dense nanocrystalline lead-free 0.942[Na0.535K0.480NbO3] - 0.058LiNbO3 (KNNLN) ferroelectric ceramic thick films (~5μm) using the aerosol deposition (AD) process. Annealed film displayed relaxor-like behavior, which is in contrast to the normal ferroelectric nature of the ceramic in its bulk form. The film exhibited a large recoverable energy density of 23.4 J/cm3 with an efficiency of over 70% under a relatively weak electric field of 1400 kV/cm. Besides, an ultrahigh power density of 38.8 MW/cm3 together with a fast discharge speed of 0.45 μs, good fatigue endurance (up to 106 cycles), and thermal stability in a wide temperature range of 20°C-160°C are also observed. The remarkable energy storage properties of AD film are correlated with its highly dense microstructure, and mechanically induced nano-sized grains with quasi-relaxor ferroelectric behavior.