Electrochemical transient investigations on the diffusion of minority charge carriers in YSZ doped by transition metal oxides

Abstract

The voltage relaxation of galvanic cells with zirconia based electrolytes polarised between an inert Pt electrode and a Pt/air electrode is analysed to obtain the diffusion coefficients of holes and electrons. The hole diffusion coefficient can be reduced by replacing zirconium with guest ions of different size, e.g. Nb5+ and Ti4+. The TZP phase with 3 mol% Y2O3 of dopant has a higher hole diffusion coefficient than the CYZ phase doped with 8 mol% Y2O3. 1 and 3 mol% p-type MnO1.5 doping increases the conductivity of holes in CYZ to a large extend, but does not influence the diffusivity. This indicates that the doping increases the hole conductivity through an increased concentration of holes. In the case of 10 and 15 mol% MnO1.5 doped Z3Y, the electronic conductivity is dominant. The chemical diffusion coefficients which are related to the oxygen vacancies were determined by GITT. The results show that the chemical diffusion coefficient of oxygen vacancies is much larger than that for holes in zirconia.