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Copolymers of vinylidene fluoride-trifluoroethylene P(VDF-TrFE) exhibit large piezoelectric ~Qd pyroelectric effects. In addition to the most common application of the pyroelectric effect (radiant detection) it is possible to'convert heat directly into electrical energy by pyroelectric conversion. This study reports the first pyroelectric conversion cycle to be measured. for the ------,copolymer-F(VDF-1=r:FE) .. It-isfound-that-standard-isotheimal-D-E-hysteresis-loopmeasurements--------are not necessarily accurate predictors of pyroelectric conversion performance for-this material. Conduction effects are found to obscure the observation of conversion cycles in most cases for the presently available materials. In spite of these difficulties, a conversion cycle was measured whose output electric energy density was 30 mJ/cm 3 • The output density isI5 times larger than any other polymer previously measured. -

A simple superconducting loop with a Josephson junction subject to a time-sinusoidal magnetic flux embedded in a noise background is considered. Cooperative effects, arising from the interplay between the noise and modulation are described; they manifest themselves in the response, measured as an output signal-to-noise ratio. In particular, it is shown that the response displays the stochastic resonance effect, wherein the output signal-to-noise ratio passes through a maximum at a critical value of the noise strength. A simple theory, based on the characterization of the superconducting quantum interference device as a bistable switching element, is seen to yield good qualitative agreement with the experimental results.

We have used in situ x-ray diffraction to measure strain curves of single crystals of 92% Pb(Zn1/3Nb2/3)O3–8% PbTiO3 poled in the 〈001〉 direction. We observed shifts in the (002) and (330) peaks as functions of applied voltage (in the 〈001〉 direction), thereby measuring the crystallographic strain. Our measurements confirm that the high strains observed using macroscopic methods reflect microscopic strains in the crystal lattice. By watching the disappearance of a rhombohedral splitting in the (330) peak, we also find direct evidence that the field-induced phase transition reported by S.-E. Park and T. R. Shrout [J. Appl. Phys. 82, 1804 (1997)] occurs between a pseudorhombohedral and tetragonal crystal structure.

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