Inception and development of micro-descharges in the voids of ferroelectrets during charging

• Applicant: Dr. Xunlin Qiu
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2007 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 39440867

During the 1990s, a number of non-polar cellular and voided polymers were discovered to exhibit strong electromechanical (quasi-piezoelectric) responses. These materials are now more and more often called “ferroelectrets”, because their polarization behavior and other related properties are macroscopically similar to those of typical ferroelectrics. In order to render ferroelectrets piezoelectric, their voids must be internally charged by means of micro-discharges (MDs) under sufficiently high external electric fields. In this proposal, we plan to study the MD phenomenon in ferroelectrets and in particular its threshold behavior by means of electrical, optical and combined electro-optical methods. The transient light emission from the voids and the transient current flow through the sample during the MDs will be investigated by means of high-speed imaging, synchronous electrical and optical detection, current-voltage measurements, and other suitable methods. Relationships between relevant parameters of the charging process, of the environment during charging, of the sample geometry and of the MD itself will be studied. Finally, a comprehensive characterization, explanation and exploitation of the relation of MDs during charging to the piezoelectric coefficients of ferroelectrets and the performance of ferroelectret-based devices will be attempted.

• DFG Programme: Research Fellowships
• Host: Professor Dr.-Ing. Reimund Gerhard