Synthesis, Structural and Electrical Properties of Lanthanum-modified Lead-zirconate-titanate System

Abstract

Lead-zirconate-titanate (PZT) ceramics with zirconate-titanate (65:35) have been synthesised with the substitution of lanthanum (6, 7 and 8 mol %). Samples were prepared by solid-state reaction route.The x-ray diffraction study shows the formation of a single phase with rhombohedral structure. There is a transformation in crystal structure from tetragonal to coexistence of tetragonal, and rhombohedral to a single rhombohedral phase with the increase in the lanthanum concentration in the basic PZT composition. Results of a detailed dielectric study indicate the diffuse-phase transition at higher values of lanthanum concentration, which may be attributed to the microscopic heterogeneity in the composition. Dielectric properties of the poled and unpoled samples have also been  compared and found that the values decreased after poling. Ferroelectric hysteresis behaviour was also studied as a function of temperature for all the three compositions, which showed typical variation of ferroelectric nature. Piezoelectric charge coefficient (d,,) decreases with increase in the lanthanum and with the increase of frequency as well, up to the measured limit.