Effects of Grain Size and Porosity on Electrical and Optical Properties of PLZT Ceramics

A group of transparent ferroelectric hot‐pressed (Pb 0.92 La 0.08 )‐(Zr 0.65 Ti 0.35 ) 0.98 O 3 specimens with controlled grain size and constant porosity and a group of similar specimens with controlled porosity and constant grain size were prepared. The electrical and optical constants and polarization‐reversal properties of these ceramics were determined as functions of grain size and porosity. When poled PLZT ceramics were aged, the polarization‐reversal characteristic was quite asymmetric, apparently because a space‐charge field, E 8p , was generated during aging. From a detailed study of the behavior of the E 8p , including its (1) generation with increasing aging time, (2) relaxation with repeated polarization reversals, (3) relaxation by heat depolarization, and (4) grain‐size and porosity dependence, it is concluded that the space‐charge layer is present inside every domain. This layer also explains the grain‐size dependencies of the remanent polarization, piezoelectric constants, and Curie point.