Effect of Excess PbO on Crystal Structure, Microstructure and Phase Transition of Lead Titanate Ceramics

Abstract

In this work, we studied the effect of excess PbO on crystal structure, microstructure and phase transition of lead titanate (PT). PT was prepared via a mixed oxide method with various PbO levels (0, 1, 3 and 5 wt.%). The raw materials were calcined at 750 oC for 2 h and sintered at 1225 oC for 2 h. The characteristics of PT were analyzed by a X-ray diffractometer (XRD), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). It was found that calcined powders and sintered ceramics indexed in a tetragonal structure. For PT powders, the impurity phases of lead oxide (PbO) and lead dioxide (PbO2) were detected in 3 and 5 wt.% of excess PbO samples, but they were not detected in all sintered ceramic samples. The increase of excess PbO levels resulted in a decreased c/a ratio in both calcined powders and sintered ceramics. Average particle sizes increased from 0.64 to 4.24 µm when excess PbO levels increased from 0 to 5 wt.%. It was also clearly seen that the liquid phase of the sintering process was obtained in the PT calcined powders which had an excess of PbO. The DSC result indicated that the phase transition temperature, from a ferroelectric to a paraelectric phase with a high PbO content (5 wt.%), was higher than those with low PbO contents (0, 1 and 3 wt.%).