Oxygen diffusion and transport properties in non-stoichiometric Ln2−xNiO4+δ oxides
Résumé
Materials formulated Ln2−x−yyCaxNiO4+δ (with (i) x = y = 0 for Ln = La, Pr, Nd, (ii) x ≠ 0 when y = 0 or y ≠ 0 when x = 0 for Ln = Nd) have been prepared and characterized using various techniques with respect to their mixed ionic/electronic conducting properties. These oxides exhibit high electronic conductivity (≈ 100 S cm− 1 at T = 700 °C) as well as high values of oxygen diffusion and surface exchange coefficients (D* and k, determined using SIMS analysis of the 18O isotope). The oxygen diffusion performances of Pr2NiO4+δ are the highest ones among those of the studied compounds. Interestingly, in the Nd-series they are slightly improved by the creation of Nd vacancies, while they are affected by the substitution of Nd by Ca.