Synthesis and structural and dielectric properties of Ca-doped PbTiO3 ceramics prepared by a hydrothermal method

In this work, perovskite ceramic materials of the composition Pb1-xCaxTiO3 (PCxT) (0 <= x <= 1) were prepared by a hydrothermal method at a relatively low temperature. In a basic environment, pressure and temperature are critical factors for the formation of a perovskite-type PCxT phase. The reaction mixture in a stoichiometric amount is placed in an autoclave and treated at 180 degrees C for 24 hours. The powder obtained after filtration and drying undergoes a grinding step and heat treatment at 400 degrees C for 4 hours. Analysis of the compounds using X-ray diffraction "XRD" and the Rietveld refinement method shows that they crystallize in a pure phase of perovskite type. Indeed, for 0 <= x <= 0.5, we observe a transformation to a pseudo-cubic phase, which confirms a good incorporation of Ca into the structure of PbTiO3 with tetragonal symmetry. For x = 0.6, in addition to the pseudo-cubic PCxT phase, a phase mixture appears. The morphology and microstructure of the samples were observed using a scanning electron microscope (SEM). Raman spectroscopy was used as an effective technique to study the structural evolution of the PCxT phase. Studying the dielectric properties of the different PCxT compounds confirms the insertion of Ca into the PT matrix and highlights its effect on the transition temperature (T-c) and the value of the dielectric constant (epsilon(r)).