Orientation mapping applied to the study of ferroelectric ceramic

Abstract

Orientation imaging microscopy (OIM) is a technique which allows crystallographic information to be obtained from samples both in scanning and transmission electron microscopes (SEM/TEM). Microstructure can be quantitatively characterized, different phases identified, and grain boundary character and morphology described. This technique based on electron backscatter diffraction (EBSD) in the SEM has shown in the last decade a spectacular advance in speed and quality of the data as well as post-processing procedures. In most cases the investigated samples are conductive and one encounters no problems connected with specimen charging. Controlling the charge and quality of the surface are the challenges for the operator running experiments on insulators. Specimen charging obscures both the forward scatter electron image and decreases the EBSD pattern quality making its analysis difficult or even impossible. Also final steps of sample preparation largely determine whether or not the pattern quality is sufficient for indexing. The influence of gas pressure and gas path length on the image quality of diffraction pattern is illustrated with the results of experiments carried out on the (PbLa)(ZrTi)O3 ceramics. Ferroelectric domains in the PLZT grains have been identified both by EBSD in the SEM and BF images in the TEM. Domains in particular grains have the same crystal orientations but different polarisation directions.