Regensburg 2007 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 31: New Materials
CPP 31.5: Talk
Friday, March 30, 2007, 11:30–11:45, H40
Charging dynamics of cellular polypropylene ferroelectrets: a combined optical and acoustic study — •Axel Mellinger, Xunlin Qiu, Michael Wegener, Werner Wirges, and Reimund Gerhard — Universität Potsdam, Institut für Physik, 14469 Potsdam, Germany
Ferroelectrets (i.e., charged cellular polymers) are rendered piezoelectric through barrier discharges inside their artificial voids [1]. Controlling and understanding the charging dynamics is a key element in the optimization of present and the development of new materials. In this work, time-resolved imaging has revealed discharge processes in individual voids and led to the discovery of a strong back-discharge glow. Simultaneous acoustic measurements of the inverse piezoelectric d33 coefficient show a “butterfly” hysteresis curve. In the framework of the presently accepted electromechanical model [2], their shape can be explained by an effective internal charge density σeff which depends both on the applied electric field and the charging history. Approx. 75 % of the internal charge density is destroyed through back discharges.
[1] S. Bauer, R. Gerhard-Multhaupt and G. M. Sessler, Physics Today 57, 37-43 (2004).
[2] M. Paajanen, J. Lekkala and H. Välimäki, IEEE Trans. Diel. Electr. Insul. 8, 629-636 (2001).