Effects of space charge on the poling of ferroelectric polymers

Abstract

Thermal pulse measurements of the polarization distribution in ferroelectric polymers and copolymers after poling give distributions concentrated to one side when the electrical conductivity under poling conditions is significantly different from zero. These results could be explained if net charge were present in the material during poling. The direct observation of distributed charge in nonpolar polymers after exposure to poling conditions support this explanation. However, high resolution laser thermal pulse measurements on nominally well poled samples of polyvinylidene fluoride reveal a sharp drop of polarization to near zero value at a depth of ∼1 μm from the surfaces which is not explained. The spatial resolution of the experiment is discussed.