DEPENDENCE OF DIELECTRIC PERMITTIVITY ON ELECTRIC FIELD FOR THICK CERAMIC-TYPE FERROELECTRIC COMPOSITE FILMS

Measuring apparatus and data processing method of dielectric permittivity at high voltage have been set up. Dependence of dielectric permittivity on electric field for thick PZT/P(VDF TrFE) and PT/P(VDF TrFE) 0-3 ferroelectric composite films has been investigated. The dielectric permittivity increases obviously with the increase of applied field for the composite with the volume fraction of ceramic φ more than 0.3. Maxwell Garnett equation can only be used to predict permittivity of the composite when φ is less than 0.1. Bruggeman equation is suitable for the prediction of dielectric permittivity of composite under low electric field (<1 MV/m). For the dependence of dielectric permittivity on electric field, good agreement is found between the measured permittivity and the prediction of Yamada model with the change of parameter L z, which indicates that L z is determined by dimension of the component, grain shape and static interaction among the grains.