Microstructural Analysis Based on Microscopy and X-Ray Diffraction

Characteristic features of ferroelectric materials are the transition in crystal structure from a cubic paraelectric phase to a lower-symmetry ferroelectric phase at the Curie temperature T c and the possibility of changing the polarization of polycrystalline materials by means of electric fields. Both features give rise to challenges with respect to X-ray analysis and microscopy

Estimation of strain from piezoelectric effect and domain switching in morphotropic PZT by combined analysis of macroscopic strain measurements and synchrotron X-ray data.

Morphotropic PZT ceramics are the state of the art materials for ferroelectric actuators. Essential performance parameters for these materials are strain and hysteresis. On a microscopic scale the strain provided by an electric field is due to two different mechanisms. The piezoelectric effect causes an elongation of the unit cells, whereas domain switching changes their crystallographic orientation by aligning the polarization axis towards the field direction. A method is outlined to estimate the contribution of the two mechanisms to total strain by combining macroscopic strain measurements and X-ray diffraction (XRD) data. Results from macroscopic measurements of remanent and unipolar strain with the corresponding data on texture, derived from in situ synchrotron radiation XRD patterns, are analyzed and evaluated by a semi-empirical approach. The method was applied to six morphotropic, LaSr doped PZT materials of different Zr/Ti ratios. Results are discussed with respect to the differences between the materials