Mixed conduction and chemical diffusion in a Pb (Zr_0.53, Ti _0.47) O₃ buried capacitor structure

Impedance spectroscopy is performed on a buried capacitor structure composed of a PZT-0.75% Nb ceramic with platinum electrodes. The ionic and electronic conductivities (σ_ion, σ_elec) are extracted from the impedance spectra using an equivalent circuit based on the premise of mixed conduction. In the temperature range 500-700 °C, a change in local p O₂ mainly affects σ_elec, suggesting that the samples are ionically compensated, i.e., [V_O ] = [V _Pb ″]. The chemical diffusion coefficient, D̃, is obtained by a conductivity relaxation technique assuming two-dimensional diffusion geometry. In comparison to BaTiO₃, or SrTiO₃, the chemical diffusivity is found to be relatively high, D̃ =2.0× 10_-4 cm² s^-1 (700 °C, in air).