Title : Effect of doping on Physicochemical characteristics of lead titanate and of barium titanate
Abstract:
Since their discovery in 1920 until the mid-1940s, the ferroelectrics constituted a class of materials fragile and difficult to exploit. This has radically changed with the discovery of ferroelectric simple oxides; the synthesis of these new materials, mainly in the form of ceramics, marked the beginning of the exploitation of the ferroelectricity, in the first rank of which is the barium titanate (BaTiO3 )(BT) and lead titanate (PbTiO3 )(PT). Today, the electro-ceramics industry produces several billion BaTiO3 -based capacitors each year. Also, Due to their interesting piezoelectric properties, nonlinear optics, electro-optics and holographic, the lead titanate derived materials have become popular in various fields of application.
Thus the doping of BT and PT is still the subject of numerous studies for the realization of agile functions at microwave frequencies (BST), or in the manufacture of transducers (PZT ceramics near the morphotropic phase boundary.
The present work deals with the effect of substitution of Ba by Gd in BaTiO3 (BGT) and of Ti by Zr in PbTiO3 (PZT) on crystalline structure and dielectric properties of these perovskite structured compounds. The BaTi1-xGdx O3 (BGT) powders , x= 0, 1, 2, 3 and 4%, were synthesized by the sol gel method and calcined in air at different temperatures and their structure characterized by X-ray diffraction (XRD). Besides, the analysis of the electric impedance of these BGT ceramics in a wide frequency range (0.1Hz-1MHz), at room temperature, have also been performed, and parameters such as capacitance, relative permittivity and dielectric losses have been determined.
Pb(Zrx ,Ti1-x)O3 (PZTx) powders, x=0, 26, 39, 52, 65, 78 and 91%, have been prepared by the conventional solid state reaction, and characterized by X-ray diffraction (XRD), Raman and Fourier transform infrared techniques, and their microstructure was investigated using Scanning Electron Microscopy (SEM). XRD spectra of the PZTx samples revealed a behavior in conformity with the phase diagram established by Jaffe et al. Dielectric analysis showed the presence of an anomaly in the ferroelectric phase of PZT, located at about 275 °C. Few studies have reported the existence of such anomalies, which we have interpreted based on structural results.
