Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 5: New Materials
CPP 5.4: Vortrag
Montag, 25. Februar 2008, 10:45–11:00, C 230
Dielectric barrier discharges in ferroelectrets: Spectroscopic characterization and pressure dependence — •Xunlin Qiu, Axel Mellinger, Werner Wirges, and Reimund Gerhard — Institute of Physics, University of Potsdam, 14469 Potsdam, Germany
In recent years, a number of cellular and voided polymer-ferroelectret materials were discovered to exhibit a strong piezoelectric response after proper charging [1]. Charging occurs via a series of dielectric barrier discharges (DBDs); this process is critical for rendering ferroelectrets piezoelectric. In the present work, the transient light emission from the DBDs in cellular polypropylene ferroelectrets subjected to high electric poling fields, and the influence of gas pressure and composition on the DBDs were spectroscopically studied. The spectrum measured in air shows strong emission from the second positive system (C3Πu → B3Πg) of molecular nitrogen (N2), and the first negative system (B2Σu+ → X2Σg+) of N2+, consistent with a DBD in air. From the strength ratios of selected vibronic bands, the electric field in the discharge was determined and found to be in good agreement with the values predicted by the Townsend breakdown model. Simultaneously, the build-up of the effective polarization of ferroelectrets under suitable voltage waveforms was studied by acoustical measurements. A polarization-voltage (P-V) hysteresis loop was obtained by analyzing the data in the light of an existing electromechanical model [2].
[1] M. Wegener and S. Bauer, ChemPhysChem 6, 1014 (2005).
[2] X. Qiu, A. Mellinger, M. Wegener, W. Wirges and R. Gerhard, J. Appl. Phys. 101, 104112 (2007).