Characterization by transmission electron microscopy of high-Zr-content lead zirconate titanate ceramics

This work presents a Transmission Electron Microscopy (TEM) study of a seri es of ceramics with compositions Pb(Zr1-xTix)O-3 (0.06 less than or equal t o x less than or equal to 0.45). Two ferroelectric rhombohedral phases have been identified within this range of compositions. Besides the characteriz ation of the domain configuration, TEM allows to obtain information of the local crystalline structure of these phases. One of the characteristics obs erved in these phases is the appearance of superlattice reflections at 1/2 {110}(p) and 1/2 {111}(p) positions of the electron diffraction patterns, w hich have not been observed by neutron or X-ray diffraction. They disappear when the paraelectric cubic phase is reached and with the increase of the Ti content. Dark field micrographs obtained with these reflections reveal d etails of the structures associated with them. The origin of these superlat tice reflections has been attributed by other authors to a system of oxygen octahedra tiltings, which cannot explain the presence of some specific ref lections. From the results we conclude that a more plausible explanation is the appearance of antiparallel displacements of cations.