Berlin 2005 – scientific programme

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DF: Dielektrische Festkörper

DF 3: FV-internes Symposium „Polare Polymere und Ferroelektrete“

DF 3.7: Talk

Saturday, March 5, 2005, 11:20–11:40, TU C130

Stacks of piezoelectric cellular polypropylene films: Characterisation of audio and ultrasound transducer properties — •Michael Wegener, Steffen Bergweiler, Olena Voronina, Werner Wirges, and Reimund Gerhard-Multhaupt — Department of Physics, University of Potsdam, Am Neuen Palais 10, 14469-Potsdam, Germany

Transducer films of cellular polypropylene typically show high piezoelectric activity with piezoelectric coefficients of several hundred pC/N or pm/V. Their piezoelectric activity can be adjusted and enhanced by suitably modifying preparation, inflation and electric charging. However, a further enhancement of the piezoelectric activity is also possible by stacking two or more transducer films. Here, we describe the piezoelectric responses that are possible with a two-layer stack of cellular polypropylene films. Piezoelectric thickness-extension resonances as well as the emitted sound-pressure levels were measured as a function of frequency and electric field in order to determine the frequency spectrum of the piezoelectric activity and to evaluate the amplification that is possible with stacking. A significant decrease of the thickness-extension resonance of the clamped transducer film within the stack was found. However, at lower frequencies in the range between 1 and around 40 kHz, a doubling of the piezoelectric response was achieved, which makes such stacks attractive for transducers operating in the audible and lower ultrasonic frequency range.