Antiferroelectric to Paraelectric Phase Transition in Lead Zirconate Thin Films

Abstract

Lead zirconate, PbZrO₃, is antiferroelectric at room temperature and has a first-order phase transition to the paraelectric state at 230°C in bulk crystals. At room temperature, the antiferroelectric Pb displacements along [110] directions produce a superstructure at the (h+¼ k+¼, 1) positions (referenced to pseudo-tetragonal unit cell). The Pb displacements occur perpendicular to the shorter c axis. In this study, the behavior of thin films was compared to the bulk. Films of lead zirconate were deposited onto electroded silicon wafers via the sol gel method. By varying the deposition conditions of the Pt substrate, films with both {111} and {100} preferred orientation were grown. The crystalline film consisted of columnar grains which were not completely aligned with each other, but had a random orientation with respect to the film's perpendicular axis. Measurements of superstructure peak intensities vs. temperature show that the thin films exhibit a much more gradual phase transition to the paraelectric state compared to the bulk. Furthermore, comparison of a and c vs. temperature show this effect, as well as a strain of about 0.5% in c. In the {100} oriented films, we found that the c-axis was oriented perpendicular to the film's surface, meaning they should be classified as (001).