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

Abstract

In this work, perovskite ceramic materials of the composition Pb_1−xCa_xTiO₃ (PC_xT) (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 PC_xT phase. The reaction mixture in a stoichiometric amount is placed in an autoclave and treated at 180 °C for 24 hours. The powder obtained after filtration and drying undergoes a grinding step and heat treatment at 400 °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 PC_xT 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 PC_xT phase. Studying the dielectric properties of the different PC_xT 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 (ε_r).