12月24日力学与空天技术系学术报告
题目：Phase Field Simulations of Ferroelectric Materials
报告人： 王 杰（Jie Wang） 博士
Institute for Materials Research II, Forschungszentrum Karlsruhe, Germany
报告内容摘要：
Ferroelectric materials have become preferred materials in a wide variety of electronic and mechatronic devices due to their pronounced dielectric, piezoelectric, and pyroelectric properties. These distinct dielectric, piezoelectric, and pyroelectric properties are related to ferroelectric domain structures and domain switching. We employed phase field models based on the time-dependent Ginzburg-Landau equation to investigate the microstructures in ferroelectrics, the polarization switching under external loadings, and the stable polarization distribution in ferroelectric nanostructures. Phase field simulations are conducted with different numerical techniques in reciprocal space and in real space, respectively, for different boundary conditions. Phase field simulations show that domain switching is a kinetic process of the disappearance of old domains and the nucleation and growth of new domains, which can not be predicted by traditional continuum models in the literature. New physical phenomena are discovered in ferroelectric nanostructures. For example, an unusual vortex state is found in ferroelectric nanotubes and nanodots with open-circuit boundary condition. When the density of surface charge exceeds a critical value or the surface is short-circuited, the in-plane polarizations disappear. It makes ferroelectric nanotubes and nanodots experience an unusual transition from a vortex state to a single-domain state. Simulation results also show that regular multi-domain structures can be obtained by means of specified surface charges. The ability to manipulate the domain patterns suggested in the present work holds promise as a method to tailor physical properties of ferroelectric nanostructures for specific applications.
报告人简介：
Dr. Wang received his Bachelor degree in Engineering Mechanics from Xi'an Jiaotong University in 1998. After that he worked as an assistant engineer (1998-1999) at Nanchang Institute of Aircraft Design and Research. He obtained his Master degree in Solid Mechanics from Lanzhou University in 2002 and PhD degree in Mechanical Engineering from the Hong Kong University of Science and Technology in 2006. Then he worked as a postdoctoral research associate (2006-2007) at the Hong Kong University of Science and Technology. Currently he is a Humboldt research fellow at Forschungszentrum Karlsruhe, Germany. His research focuses on the modeling and simulation of ferroelectric materials including the relationship between microstructures and properties, nonlinear fracture and ferroelectric nanostructures.
主持人：段慧玲 特聘研究员
时间：12月24日（周三）下午1:30
地点：力学楼434会议室
欢迎广大师生光临！要求力学系教师参加，会后进行投票。
报告人： 王 杰（Jie Wang） 博士
Institute for Materials Research II, Forschungszentrum Karlsruhe, Germany
报告内容摘要：
Ferroelectric materials have become preferred materials in a wide variety of electronic and mechatronic devices due to their pronounced dielectric, piezoelectric, and pyroelectric properties. These distinct dielectric, piezoelectric, and pyroelectric properties are related to ferroelectric domain structures and domain switching. We employed phase field models based on the time-dependent Ginzburg-Landau equation to investigate the microstructures in ferroelectrics, the polarization switching under external loadings, and the stable polarization distribution in ferroelectric nanostructures. Phase field simulations are conducted with different numerical techniques in reciprocal space and in real space, respectively, for different boundary conditions. Phase field simulations show that domain switching is a kinetic process of the disappearance of old domains and the nucleation and growth of new domains, which can not be predicted by traditional continuum models in the literature. New physical phenomena are discovered in ferroelectric nanostructures. For example, an unusual vortex state is found in ferroelectric nanotubes and nanodots with open-circuit boundary condition. When the density of surface charge exceeds a critical value or the surface is short-circuited, the in-plane polarizations disappear. It makes ferroelectric nanotubes and nanodots experience an unusual transition from a vortex state to a single-domain state. Simulation results also show that regular multi-domain structures can be obtained by means of specified surface charges. The ability to manipulate the domain patterns suggested in the present work holds promise as a method to tailor physical properties of ferroelectric nanostructures for specific applications.
报告人简介：
Dr. Wang received his Bachelor degree in Engineering Mechanics from Xi'an Jiaotong University in 1998. After that he worked as an assistant engineer (1998-1999) at Nanchang Institute of Aircraft Design and Research. He obtained his Master degree in Solid Mechanics from Lanzhou University in 2002 and PhD degree in Mechanical Engineering from the Hong Kong University of Science and Technology in 2006. Then he worked as a postdoctoral research associate (2006-2007) at the Hong Kong University of Science and Technology. Currently he is a Humboldt research fellow at Forschungszentrum Karlsruhe, Germany. His research focuses on the modeling and simulation of ferroelectric materials including the relationship between microstructures and properties, nonlinear fracture and ferroelectric nanostructures.
主持人：段慧玲 特聘研究员
时间：12月24日（周三）下午1:30
地点：力学楼434会议室
欢迎广大师生光临！要求力学系教师参加，会后进行投票。