Switching of polycrystalline lead zirconate titanate

Measurements are described of the switching currents in polycrystalline lead zirconate titanate as a function of time and applied electric field. Samples of three compositions were investigated: Pb(Zr0·65 Ti0·35)0·99 Nb0·01 O3, Pb(Zr0·52 Ti0·48)0·99 Nb0·01 O3 and Pb Zr0·55 Ti0·45 O3. The results of these measurements show that the switching current has an exponential dependence on the reciprocal of the applied electric field, in a manner similar to that measured previously for single-crystal ferroelectric materials, and that the materials have no true coercive field. Activation fields and switching currents have been measured. A theoretical treatment of switching in polycrystalline materials is given and good agreement between the experimental data and the theory has been obtained by considering the polycrystalline material to be an assembly of randomly oriented single crystals. For low electric fields the currents through all the lead zirconate titanate materials showed an intermittent switching behaviour which was probably due to the statistical nature of the nucleation process in the different regions of the ceramic material.