Polarization switching at the nanoscale in ferroelectric copolymer thin films Appl. Phys. Lett. 99, 142904 (2011) Tunable temperature dependence of electrocaloric effect in ferroelectric relaxor poly(vinylidene fluoridetrifluoroethylene-chlorofluoroethylene terpolymer Appl. Phys. Lett. 99, 052907 (2011) Beneficial and detrimental fatigue effects of dielectric barrier discharges on the piezoelectricity of polypropylene ferroelectrets J. Appl. Phys. 110, 024108 (2011) Energy harvesting by nonlinear capacitance variation for a relaxor ferroelectric poly(vinylidene fluoridetrifluoroethylene-chlorofluoroethylene) terpolymer Appl. Phys. Lett. 98, 222901 (2011) Photocrosslinking of ferroelectric polymers and its application in three-dimensional memory arrays Appl. Phys. Lett. 98, 183302 (2011) Additional information on J. Appl. Phys. We describe the concept, the fabrication, and the most relevant properties of a piezoelectric-polymer system: Two fluoroethylenepropylene ͑FEP͒ films with good electret properties are laminated around a specifically designed and prepared polytetrafluoroethylene ͑PTFE͒ template at 300°C. After removing the PTFE template, a two-layer FEP film with open tubular channels is obtained. For electric charging, the two-layer FEP system is subjected to a high electric field. The resulting dielectric barrier discharges inside the tubular channels yield a ferroelectret with high piezoelectricity. d 33 coefficients of up to 160 pC/N have already been achieved on the ferroelectret films. After charging at suitable elevated temperatures, the piezoelectricity is stable at temperatures of at least 130°C. Advantages of the transducer films include ease of fabrication at laboratory or industrial scales, a wide range of possible geometrical and processing parameters, straightforward control of the uniformity of the polymer system, flexibility, and versatility of the soft ferroelectrets, and a large potential for device applications e.g., in the areas of biomedicine, communications, production engineering, sensor systems, environmental monitoring, etc.

The photoluminescence observed in ABO3 type perovskite in their highly structural disordered state can be explained by a model in which is assumed a distribution of electronic states localized within the energy band gap coupled to lattice local vibrational states. The model fits very well the experimental results and indicates that photoluminescence in the visible region can be considered as a general behavior of disordered solids.

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