Interaction between proton conducting BaCe_0.2Zr_0.7Y_0.1O₃ electrolyte and structural ceramics during sintering

The chemical compatibility of thin electrolyte layers and their support materials at high temperatures is crucial for the performance in solid oxide cells and membranes. This work describes the chemical interaction between the electrolyte material, BaCe_0.2Zr_0.7Y_0.1O₃ + 0.5 wt% NiO (BCZY), and structural ceramics Al₂O₃, 8 mol% yttria stabilized zirconia (8YSZ), TiO₂, CeO₂ and MgO during sintering. 1:1 wt% powder mixtures of the electrolyte material and structural ceramics were annealed at 1500 °C for 5 h, with the phase composition being determined through XRD analysis at room temperature. Subsequently, the material interaction between BCZY films deposited on the most promising structural ceramic MgO was investigated by SEM and EDS. In particular, the complex sintering requirements to form single-phase BCZY electrolyte layers is troubled upon coating and sintering BCZY on MgO. Hereby, the diffusion of NiO into the MgO support leads to a deficiency of NiO in the BCZY layer, making the solution and precipitation mechanism required to form the perovskitic phase unable to occur. In extreme scenarios, the electrolyte layer depletion of NiO can even cause the decomposition of a single-phase BCZY into BaZrO₃, Ce-Y fluorite and a BCZY perovskite phase of undefined composition.