Redistribution of Ce and La during processing of Ce(La)-TZP/Al2O3 composites

Abstract The dispersion of second-phase particles, platelets or fibres in a ceramic body offers possibilities of considerable improvements in mechanical properties. In such second-phase reinforced composites the materials properties are to a large extent controlled by the structure of the internal interfaces, i.e. the phase and grain boundaries. The microstructure/microchemistry of aluminadispersed ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP/20A) were characterized by means of analytical TEM/STEM techniques. Local variation in the concentration of Ce stabilizer as well as of La additives and Si impurities during processing of the composite ceramics were studied by EDS X-ray analysis with high spatial resolution. Emphasis was put on the segregation of Ce and La in interface regions. Evidence was found for the presence of a vitreous intergranular phase situated in small pockets at triple grain junctions. The addition of small fractions of La 2 O 3 in TZP resulted in interreaction between matrix constituents and Al 2 O 3 particles. In this reaction a stable crystalline Al-Ce-La-Zr mixed oxide phase is formed, effectively reducing the fraction of residual vitreous intergranular phase, resulting in improved fracture toughness in this material.