The Whitehead Memorial Lecture
The Whitehead Memorial Lecture is named in honor of Dr. John Boswell Whitehead, a pioneer in electrical insulation and dielectrics and a long-time contributor to the CEIDP. The Conference opens each year with the Lecture and it is the keynote session of the Conference. The 2018 Whitehead Memorial Lecture will be given by Prof. Dr.-Ing.-Habil. Herbert Kliem.
The Whitehead Lecture 2018: Dielectric Relaxation and Ferroelectric Imprint
Abstract—The term imprint is generally used for a special kind of a reversible change in the ferroelectric state. It refers to a time dependent resistance of the material against polarization reversal. At the example of P(VDF-TrFE) it is shown that polarized to the remanent polarization and under a switched off external field the coercive field of the sample’s hysteresis loop increases in time, the ferroelectric switching time increases as well, the remanent polarization decreases, and the small signal ac capacitance decreases also. All four effects exhibit on a logarithmic time scale a linear behavior, i.e. they are proportional to log tw, with tw as the waiting time after switching off the external field. A model is developed which relates the four observations. The model is based on a feedback effect between a crystalline phase where the ferroelectric switching takes place and an amorphous phase with a relaxational polarization response.
Herbert Kliem received the diploma in electrical engineering with the subject area solid state electronics and the degree Dr.-Ing., both at the University of Technology Aachen, Germany. In 1991 he joined the Technical University Hamburg-Harburg and achieved the qualification as a university lecturer. Since 1996 he has been a full-time professor and head of the Institute of Electrical Engineering Physics at the Saarland University. In 1982 he attended the CEIDP for the first time. Since then he has contributed 29 manuscripts to the Annual Report.