Elaboration et caractérisation de céramiques PZT dopé et détermination de la frontière morphotropique (FMP)

Abstract

This work has for objective, the synthesis and development, the survey of the dielectric, piezoelectric and mechanical properties of a new material made by ceramics PZT type of structure perovskite in the ternary system: (1-x)Pb (Zry Ti1-y)O3-xSm(Fe3+ 0.5, Nb5+ 0.5)O3 with x = 2%, 41%≤ y ≤57%. A substitution in site A and B was carried out in order to ameliorate its physical properties. The samples chosen for this survey have been prepared by a synthesis method in strong way. The samples have undergoes a sintering with: 1100, 1150, 1180 oC successively, in order to optimize the temperature of sintering where the density of the sample is maximal (near to the theoretical density) and therefore the product of better physical quality. Different techniques of characterization have been used for this survey as, the diffraction of the X-rays, the scan electronic microscopy (SEM), atomic force microscopic (AFM) and the electric measures. The diagrams of diffraction of the X-rays indicated that the compositions near to the MPB, are located in the range 51≤ y ≤55% and the morphological survey of the different samples showed that the ceramics PZT-SFN (55/45) sintered to 1180 oC near to the MPB favored the growth of the grains. The survey of the dielectric properties of all samples showed a strong dielectric constant for the two samples 53/47 (εr=13583,036) and 55/45 (εr=13072,59), a lower loss constant 1,29 % for the sample 53/47 and 1,258 % for the sample 55/45 supposed to be near the morphotropic phase boundary where coexists the two phases tetragonal (T) and rhombohedral (R). The survey of the piezoelectric properties of the two samples 53/47, 55/45 also showed a maximal value of the planar electromechanical coupling factor (0,63 for the sample 53/47 and 0,619 for the sample 55/45). These results are similar to the results found by other authors.