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

Tetragonal La-modified lead zirconate titanate ceramics with a Zr/Ti ratio of 40/60 (x/40/60) with La contents (x) between 0 and 21 at. % were prepared by the mixed oxide method and were subsequently characterized using dielectric spectroscopy. Small La contents tended to diffuse the dielectric response in the temperature region around the phase transition, however, no distinct changes were observed in the paraelectric region. Compositions with intermediate La contents showed a thermally driven (spontaneous) transformation from a relaxor to a normal ferroelectric, i.e., micro-macro domain switching. Materials with a high La content exhibited typical relaxor ferroelectric behavior. The relative thermodynamic stability of the ensemble of micropolar regions is then discussed in reference to that of the long-range ferroelectric state.