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

Accurate impedance measurements on differently sized samples of lead-zirconate-titanate (PbZr0.53Ti0.47O3, PZT) have been analyzed with a CNLS procedure, resulting in the separation of the ionic and electronic conductivities over a temperature range from similar to 150 to 630 degreesC. At 603 degreesC the electronic conductivity shows approximately a (Po-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 Po-2. A tentative interpretation assumes defect association, i.e. formation of neutral [V-Pb"-Vo](x) 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 degreesC under low oxygen pressure (similar to 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. (C) 2004 Elsevier B.V. All rights reserved.