Yb-doped ceria with a composition of Ce0.8Yb0.2O1.9 was used to coat SiC fibers by a solution immersion route using Ce(NO3)3 and Yb(NO3)3. The phase compatibility between the fibers and the coating layer was studied in an Ar atmosphere and in air at 1100o-1300oC. The heat-treatment of the mixture of Yb-doped ceria/SiC fibers with an Al sintering additive (<1 mass%) in an Ar atmosphere at 1300oC produced CeAlO3 and 7Ce2O3·9SiO2. Subsequent heating of the fibers in air at 1100o-1300oC decomposed the CeAlO3 and 7Ce2O3·9SiO2 into CeO2, Al2O3 and SiO2. The SiC fibers coated with Yb-doped ceria and 80 mass% mullite-20 mass% alumina sheets of 75 μm thickness, were laminated and hot-pressed at 1200oC in an Ar atmosphere. The as hot-pressed composite with 15 vol% fibers and the composite subsequently heated in air at 1100oC showed ductile and brittle properties in the stress-strain relations, respectively. These results were associated with the phase stability at the interfaces between the fibers and matrix.

Keywords: Yb-doped ceria, Interface, SiC fibers, Phase compatibility, Mullite-alumina matrix, Hot-pressing