题目：Past, Present, and Future of Alternative Current Poling for Piezoelectric Materials
报告人：Prof. Yohachi Yamashita
Toyama Prefectural University, Japan（日本富山县大学）
Department of Mechanical and Airspace Engineering, NCSU, USA（美国北卡罗来纳州立大学）
报告人简介：Prof. Yohachi (John) Yamashita joined Toshiba Corp. in 1969 and started piezoelectric, dielectric, transducer, relaxor single crystal materials research. He wrote 130 peer-reviewed papers, 320 Japanese and international patents, 7 book chapters and one book. He received his Ph.D. degree in Materials Science from Waseda Univ., Japan in 1998. The most well-known research by Dr. Yamashita is recognized as relaxor single crystals for diagnostic medical ultrasonic transducers in 1997-2013. He is an inventor of the Smart AC Poling (SACP) of piezoelectric relaxor single crystals. The Pb(In,Mg,Nb)O3-PbTiO3 single crystal poled by the SACP showed the world-record-high piezoelectric constant d33>3800 pC/N. After retiring from Toshiba in 2013, he started his current post as a research specialist at the Dep. of Intelligent Systems Design Engineering in Toyama Prefectural Univ., Toyama, Japan. His current research is focused on sonic and ultrasonic stimulation for aquaculture fishes, plants, small mammals, and mankind. He was a head editor of Japan Journal of Applied Physics from 1995 to 2000. He is a fellow of Japan Society of Applied Physics and a senior member of IEEE UFFC. From Aug. 2017, he is an adjunct professor of Mechanical and Aerospace Engineering at North Carolina State University (NCSU), NC, USA. He is also a consultant of several private companies in Japan, Korea, and China.
报告内容：Alternative Current Poling (ACP) process for bulk piezoelectric materials was first reported by Ogawa Toshio of Shizuoka Science University, Japan in 2003 (Jpn Patent Publication 2003-282936). The material was Lead Zinc NiobateTitanate (PZN-9PT) single crystal (SC). After the first report, Hanue of Konica Minolta MG Co. Japan reported ACP effect for 3-0 composite of organic materials, such as PVDF and Pb free inorganic materials of CaBi4Ti4O15 (Jpn Patent Publication 2008-47693). However, both of them could not show a distinct differences of dielectric and piezoelectric properties of these materials between normal Direct Current Poling (DCP) and ACP process. In 2008, Yamamoto and Yamashita started various types of nano-composite electrodes for relaxor-PT SC to increase the coercive field (Ec) of lead magnesium niobatetitanate (PMN-30PT) SC. In the course of the R&D. we found PMN-PT SC with a special nano-composite electrode poled by ACP SC (d33=2500 pC/N) was apparently different from DCP SC sample (d33=1800 pC/N). In the beginning of the finding, we have though the reason is mainly the special nano-composite material. But after many experiment, we found the big difference was contributed by not nano-composite, but mainly the ACP process.