In situ XRD and TGA/DTA study of multiphase La- and Nd-substituted Pr2NiO4 under IT-SOFC cathode operating conditions

Abstract

Promising cathode materials Pr2−x(La/Nd)xNiO4+δ (x = 0, 0.5, 1) for intermediate temperature solid oxide fuel cells (IT-SOFC) were synthesised via a Pechini route. The samples were studied by in situ XRD in the conditions close to operating for IT-SOFC cathode. For all the samples a phase inhomogeneity was determined, manifesting itself in the apparent presence of two phases with the same 1st order Ruddlesden-Popper structure. The two phases had different unit cell parameters and slightly different phase transition (sp.gr. Fmmm ↔ I4/mmm) temperatures. For the as-synthesised PrNdNiO4+δ sample a loss of crystallinity, accompanied by a release of H2, H2O, CO2 and CO gases upon heating in an inert atmosphere, was observed. The crystallinity of the sample was recovered upon subsequent heating in an air atmosphere. La- and Nd- doping increased thermal stability of samples compared to the undoped one in air at 700 °C. In situ XRD experiments were supplemented by TGA/DTA measurements performed in the same conditions.