DIELECTRIC-PROPERTIES OF TETRAGONAL LANTHANUM-MODIFIED LEAD-ZIRCONATE-TITANATE CERAMICS

Tetragonal La-modified lead zirconate titanate ceramics with a Zr/Ti r atio of 40/60 (x/40/60) with La contents (x) between 0 and 21 at. % we re prepared by the mixed oxide method and were subsequently characteri zed using dielectric spectroscopy. Small La contents tended to diffuse the dielectric response in the temperature region around the phase tr ansition, however, no distinct changes were observed in the paraelectr ic region. Compositions with intermediate La contents showed a thermal ly driven (spontaneous) transformation from a relaxor to a normal ferr oelectric, i.e., micro-macro domain switching. Materials with a high L a content exhibited typical relaxor ferroelectric behavior. The relati ve thermodynamic stability of the ensemble of micropolar regions is th en discussed in reference to that of the long-range ferroelectric stat e.