Ionic and electronic conductivity in lead–zirconate–titanate (PZT)

Accurate impedance measurements on differently sized samples of lead–zirconate–titanate (PbZr 0.53Ti 0.47O 3, PZT) have been analyzed with a CNLS procedure, resulting in the separation of the ionic and electronic conductivities over a temperature range from ∼150 to 630 °C. At 603 °C the electronic conductivity shows approximately a ( P O 2 ) 1/4 dependence, while the ionic conductivity remains constant. Below the Curie transition temperature the oxygen non-stoichiometry becomes frozen-in and the conductivities are strongly dependent on the sample history with respect to temperature sequence and ambient P O 2 . A tentative interpretation assumes defect association, i.e. formation of neutral [V Pbʺ–V O ··] × complexes, and electron-hole transfer between lead sites and lead vacancies to control the oxygen ion conductivity in the tetragonal phase. Annealing PZT-based devices at about 600 °C under low oxygen pressure (∼1 Pa oxygen) effectively decreases the low temperature electronic conductivity by a factor of 100 and the ionic conductivity by a factor of 10–15 with respect to normal air processing.