Partial conductivities and chemical diffusion in donor-doped lead zirconate titanate (PZT)

Abstract

Also in case of donor doping, lead zirconate titanate may exhibit a significant oxygen vacancy concentration. This can be attributed to the only partially controllable loss of lead oxide during preparation. Accordingly, many questions are still to be solved regarding oxygen chemical diffusion and partial conductivities of ions and electrons in PZT.<br />In this work, the results of an impedance spectroscopic study on Nd-doped PZT are presented. Temperature and oxygen partial pressure were varied and corresponding time-dependent and steady state measurements allowed conclusions on the nature of the conducting charge carriers (electrons, holes, oxygen vacancies) and the chemical diffusion coefficients. It will be shown that substantial oxide ion conduction sets in at temperatures above 600 °C and leads to additional features in impedance spectra measured with ionically blocking electrodes and finally to thermally induced irreversible changes of the material. From the corresponding capacitance and resistance observations oxygen vacancy concentrations and mobilities can be estimated and compared to complementary degradation and tracer diffusion studies.<br />Furthermore theoretical calculations are performed using WIEN2k to get an insight into optical changes of PZT during electrical field driven experiments - blackening - or during exposition in hydrogen.