Development of solid oxide cells by co-sintering of GDC diffusion barriers with LSCF air electrode

The effects of a Cu-based additive and nano-Gd-doped ceria (GDC) sol on the sintering temperature for the construction of solid oxide cells (SOCs) were investigated. A GDC buffer layer with 0.25-2 mol% CuO as a sintering aid was prepared by reacting GDC powder and a CuN2O6 solution, followed by heating at 600 °C. The sintering of the CuO-added GDC powder was optimized by investigating linear shrinkage, microstructure, grain size, ionic conductivity, and activation energy at temperatures ranging from 1000 to 1400 °C. The sintering temperature of the CuO-GDC buffer layer was decreased from 1400 °C to 1100 °C by adding the CuO sintering aid at levels exceeding 0.25 mol%. The ionic conductivity of the CuO-GDC electrolyte was maximized at 0.5 mol% CuO. However, the addition of CuO did not significantly affect the activation energy of the GDC buffer layer. Buffer layers with CuO-added GDC or nano-GDC sol-infiltrated GDC were fabricated and tested in co-sintering (1050 °C, air) with La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF). In addition, SOC tests were performed using button cells (active area: 1 cm2) and five-cell (active area: 30 cm2/cell) stacks. The button cell exhibited the maximum power density of 0.89 W cm−2 in solid oxide fuel cell (SOFC) mode. The stack demonstrated more than 1000 h of operation stability in solid oxide electrolysis cell (SOEC) mode (decay rate: 0.004%/kh).