Directionally solidified CeO2 (or GDC)/CoO eutectic ceramics as cermet precursors for SOFCs anodes: Microstructure cross-over

Rods of CeO2 and gadolinium-doped CeO2 (GDC)–CoO eutectics were prepared by directional solidification using a laser heated floating zone (LFZ) technique. The microstructure has been studied as a function of the growth rate from V = 10 to 750 mm/h. Regular eutectic microstructures are obtained except for the highest growth rate. The interspacing follows the λ2V = C law with C = 4.1(3) × 10−17 and 2.6(3) × 10−17 m3/s for CeO2–CoO and GDC–CoO eutectics, respectively. A cross-over between fibrous and lamellar eutectic microstructures was observed depending on the growth rate. The crystallography of the eutectics was studied by Electron Backscatter Diffraction (EBSD). The growth directions [1 1 0]GDC ∼ //[110]CoO, and the interfacial planes (200)GDC//(111)CoO, were identified. Solubility of Co in the ceria matrix was determined by Energy Dispersive X-ray (EDX) Spectroscopy after Co was leached out from the matrix. Co solubility in ceria at 1650 °C was found to be less than 1 mol%.