Regensburg 2007 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Relaxor Ferroelectrics

DF 3.8: Vortrag

Montag, 26. März 2007, 17:10–17:30, H11

Stability of polypropylene ferroelectrets against ionizing alpha-radiation — •Mario Dansachmüller, Ivan Minev, Francisco Camacho-Gonzalez, Simona Bauer-Gogonea, Reinhard Schwödiauer, and Siegfried Bauer — Soft Matter Physics, Johannes-Kepler University, Altenbergerstraße 69, 4040 Linz, Austria

Cellular polypropylene (cPP), a thin foil containing flat lens-like voids displays similarities to ferroelectric materials, after internally charging the surfaces of the voids, hence cPP is called a ferroelectret. The piezoelectric coefficient of charged cPP is proportional to the effective surface charge on the voids. By analyzing the nonlinearities in the current response of a charged cPP capacitor upon application of a sinusoidally varying ac-voltage, the piezoelectric response of cPP is directly determined from an electrical measurement alone. Samples of cPP with a density of 330 kg/m* were irradiated by ionizing alpha-radiation of a Ra-226 (4.87 MeV) or an Am-241 (5.64 MeV) source for several hours corresponding to doses of up to 2000 Gy or 20 000 rad. The charge decay was measured in-situ during the irradiation by continuously recording the first and second harmonic contribution of the current response, by means of digital lock-in amplifiers. A decay of the relative surface charge of 5 % was observed for a dose of 50 Gy. The smallest resolvable dose in a temperature controlled measurement was found to be 1.4 Gy.