Influence of texture on the switching behavior of Pb(Zr0.70Ti0.30)O3 sol-gel derived thin films

Rhombohedral Pb(Zr0.70Ti0.30)O3 thin films of four different well-defined textures, namely, (100), (111), bimodal (110)/(111), and (100)/(111), were prepared by a sol-gel method. The films were characterized in terms of grain size, presence of second phases, surface roughness, columnarity of grains, and other microstructural features. The dielectric, ferroelectric, and fatigue properties were investigated, with emphasis on the hysteresis switching characteristics. Results are discussed from the reference point of the allowable spontaneous polarization directions available for the different textures. The values of coercive field, remanent and saturation polarization, and slope of the loop at the coercive field, at saturating fields can be qualitatively explained based on the texture, independent of microstructural differences. The occurrence of surface pyrochlore, however, is observed to affect the functionality of the saturation curves, particularly for the samples of bimodal texture. Shearing of the hysteresis curves of the bimodal films is also attributed to surface microstructural features. The occurrence of nonswitching 71° or 109° domains in the (111) and (110)/(111) textured films is hypothesized based on a comparison with the data from the (100) textured film. Corrected saturation polarization values agree with the spontaneous polarization values of rhombohedral PZT single crystals and published calculated values for rhombohedral PZT ceramics. The fatigue characteristics show increases in the switching component of polarization in the range 103−107 bipolar cycles, particularly for the (111) textured sample. Onset of fatigue is observed for all samples between 107 and 108 switching cycles.