Electric field-induced changes of domain structure and properties in La-doped PZT—From ferroelectrics towards relaxors

Electromechanical properties and crystal and domain structures of piezoelectric ceramics from the Pb1−xLax(Zr0.65Ti0.35)1−x/4O3 (x/65/35 PLZT) solid solution system were systematically analysed by electrical measurements, X-ray diffraction and scanning electron microscopy. The compositionally-driven phase transition from a rhombohedral ferroelectric into a pseudocubic relaxor state is accompanied by a decrease in domain size and changes in domain morphology. SEM analyses of the ex-situ poled samples showed that only in the ferroelectric compositions domain configuration changed, while in the relaxor compositions no domain changes were detected. In order to evaluate the extrinsic contribution to enhanced piezoelectric properties in relaxors, in-situ environmental scanning electron microscopy analyses with applied external electric field were performed. Extrinsic effects as a result of poling were predominant in the ferroelectrics, whereas the intrinsic effect prevailed in the relaxors. Finally, a model of electric field-induced displacements as a result of decreasing domain size for the ferroelectric-to-relaxor PLZT materials was proposed.