Investigation and optimization of interface reactivity between Ce_0.9Gd_0.1O_1.95 and Zr_0.89Sc_0.1Ce_0.01O_2-δ for high performance intermediate temperature-solid oxide fuel cells

The effects of cobalt addition on the sintering, thermal, and electrical properties of Ce_0.9Gd_0.1O_1.95 (GDC) and Zr_0.89Sc_0.1Ce_0.01O_2-δ (ScSZ) were investigated. A small addition of cobalt oxide remarkably enhanced the sinterability of GDC, especially for GDC powder with a specific surface area of 40 m² g^-1, which was synthesized via a citrate method. Relative densities of approximately 95% can be achieved for GDC pellet samples using 2 mol% Co dopant and sintering at 1100 °C for 10 h. The thermal expansion and electrical conductivity of 2 mol% Co-doped GDC were comparable to those of the non-doped sample. The thermal expansion of ScSZ with various amounts of Co addition was linear in both oxidizing and reducing atmospheres. The electrical conductivity of Co-doped ScSZ decreased with increasing Co content; however, this decrease was not dramatic. These results suggest that the addition of cobalt oxide is a promising method for obtaining GDC buffer layers that are sinterable at low temperatures for use in intermediate temperature-solid oxide fuel cells.