Effect of small amounts of impurities from raw materials on the sintering behavior of highly pure PZT ceramics

The sintering behavior of PZT ceramics was monitored in situ by a thermooptical measuring device. By that, the effect of a small amount of impurities on sintering kinetics was investigated. When highly pure TiO2 was replaced by industrially used one to synthesize PZT, the intermediate formation of PbTiO3 was shifted to a lower temperature. This reduced the lead loss during calcination and improved sintering. Liquid phases were formed during sintering, due to an PbO excess, which was attributed to deviations from PZT stoichiometry caused by the impurities. Some impurities also were dissolved in the liquid phase, thus highly enhancing the densification process.