Artificial Crystal Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences
题目：Recent Developments on Piezoelectric Materials
报告人：Prof. Shujun Zhang, 澳大利亚伍伦贡大学（University of Wollongong, Australia）
报告人简介：Prof. Shujun Zhang received Ph.D. from Shandong University, China, in 2000. He is Future Fellowship Professor at ISEM/AIIM of University of Wollongong, prior to which, he is senior Scientist at Materials Research Institute and Professor at Materials Science and Engineering Department of The Pennsylvania State University. He is associate editor for IEEE Transaction UFFC, Journal of the American Ceramic Society, Journal of Electronic Materials and Science Bulletin, he is the section Editor-in-Chief for “Crystal Engineering” section of the MDPI journal, Crystals. He was a recipient of the Ferroelectrics Young Investigator Award of IEEE UFFC Society in 2011. He is senior member of IEEE and elected AdCom member of the IEEE UFFC society during 2016-2018. He holds six US patents and has authored/coauthored more than 380 papers in refereed journals, with SCI citations of >10,000 and H index of 49. He is now focusing on the fabrication- microstructure- property- performance relationship of high performance piezoelectric crystals and ceramics, including lead free materials, for sensor, transducer and energy storage/harvesting applications
报告内容：Piezoelectric materials play an important role in electromechanical applications, such as medical imaging, structural health monitoring (SHM) and nondestructive evaluation. To improve the performance of electromechanical devices, the selection of piezoelectric material with optimized properties is a critical concern. In this presentation, the history and applications of piezoelectric materials have been reviewed, with emphasis on recent developments of piezoelectrics, where the discussion is divided into two parts, i.e., ferroelectric and nonferroelectric materials. Special attention is focused on the temperature dependence of electromechanical properties and related mechanisms of piezoelectric materials, the potential piezoelectric materials for cryogenic and ultra-high temperature applications are also discussed. The uniqueness of relaxor-PT crystals and nonferroelectric piezoelectric crystals are surveyed for possible electromechanical applications. Specifically, relaxor-PbTiO3 single crystals show superior piezoelectric properties, with piezoelectric coefficients of >2000pC/N and electromechanical coupling factors of >90%, far outperforming conventional ferroelectric PZTs, which greatly benefit medical ultrasound imaging. Furthermore, good piezoelectric properties are found down to cryogenic temperatures, being on the order of 200pC/N at 20K. In contrast, nonferroelectric single crystals, such as langasites, oxyborates, melilite and fresnoite crystals, possess ultrahigh electrical resistivity, being on the order of 108Ohm.cm at 500oC. Though their piezoelectric coefficients fall into single digits, they are promising for high temperature sensing applications, up to 1200 oC. In addition, new development on lead free single crystals is also reviewed.