Conduction and aging of piezoelectric PZT ceramics

In order to lower the electrical conductivity and increase resistance to aging of piezoelectric PZT ceramics, solid solutions containing as few vacancies as possible were made. The usual dry process through reaction between solids was unsuitable owing to the volatility of lead oxide at the high temperatures of reaction (900 C) and of sintering (1300 C) but using a coprecipitation method all the cations initially brought in the process are present in the final solid. A model of a superstructure polarizable through electron transfer between cationic sites suffices to justify the space charge compensation in polarized ceramics, and therefore the stability of these ferroelectrics. A lead vacancy should also induce the creation of a Pb4(+) ion, but here both vacancy and Pb4(+) ion can move under stress, which decreases the stability of polarization phases.