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Piezo- and pyroelectric behaviour of corona-charged polyvinylidene fluoride

Biaxially stretched polyvinylidene-fluoride (PVF2) films of 25 mu m thickness were poled by corona charges at surface potentials of 10 and 5 kV. X-ray diffraction studies suggest that structural changes from the non-polar Form 2 type to the polar Form 1 type occur, via an intermediate polar Form 2 type, in PVF2 on corona charging. The similarity in behaviour of the reversible pyroelectric coefficient p, and the piezo-electric strain coefficient d31 with temperature suggest that these two phenomena in PVF2 may have a common origin.