DIFFUSION BONDING OF NIOBIUM AND Y2O3-STABILIZED ZRO2 OR HFO2

Y2O3-stabilized ZrO2 or HfO2 single crystals with (100), (110), or (111) surface are diffusion-bonded to polycrystalline niobium, and then joints are tensile tested. The bond strength is dependent on the surface orientation of ZrO2 or HfO2: higher bond strength is obtained in the (100) and (110) surfaces than in the (111) surface. Although any reaction layers are not observed by EPMA at the bonding interface, black dots are found on the torn surfaces of both the ceramic and the metal in the joints bonded at 1 773 K and above and then tensile tested, which may imply that some reaction has occurred at the bonding interface. Lattice matching is also considered for observed crystallographic orientation relationships.