Berlin 2001 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 5: Composites

CPP 5.3: Talk

Tuesday, April 3, 2001, 18:25–18:45, 111

Excess charges in heterogeneous materials: A new route for piezoelectricity — •Simona Bauer-Gogonea, Gerhard S. Neugschwandtner, Reinhard Schwödiauer, and Siegfried Bauer — Applied Physics, Johannes-Kepler-University Linz, Austria

In solid state physics, piezoelectricity is defined from the free-energy in a rigorous but restrictive way as an intrinsic property of noncentrosymmetric crystal classes. On the basis of a practical transducer and actuator definition, the class of piezoelectric materials is much broader, including the recently found charged No-dqpiezoelectricNo-dq space-charge electrets with heterogeneous material properties. Material heterogeneity combined with electrical charging offers non-conventional routes for symmetry breaking and for the preparation of piezoelectric materials with tailored piezoelectric properties. Simple model systems based on "softNo-dq and No-dqhardNo-dq polymers with known mechanical and electrical properties enable the calculation of the piezoelectric properties and electromechanical coupling coefficients and may serve as a guide in the selection of new materials. Materials employed for the single- and hybrid multilayer structures include micro- and nanoporous polytetrafluoroethylene, polypropylene foams, as well as fluorethylenepropylene and polyvinylidene fluoride. An overview is given on the thermal, elastical, acoustical, dielectric, piezo- and pyroelectric properties.