First-principles study on stability, adhesion and fracture properties of ZrO2/W interface in composite materials

Zirconia/tungsten (ZrO2/W) interface is easily formed during the preparation of W-Zr and W-ZrC composites for plasma-facing materials. But there is little information available about the stability, cohesion and bonding of ZrO2/W interface at the atomic scale. Therefore, the thermodynamic stability, mechanical properties and electronic structure of t-ZrO2(001)/W(001) interfaces have been calculated using first-principles calculations. Five kinds of interface bonding structures were considered, and it is found that the two sandwich-like interfaces with one or two stoichimetric ZrO2(001) layers between two W(001) slabs have lower interface energies and better stability than the three precipitate-like interfaces with a ZrO2(001) slab stacked on a W(001) slab, which means that an ultrathin zirconia film tends to form and may promote the grain refinement in W. The analyses of mechanical properties including the work of separation, fracture energy and tensile strengths show that the mechanical failure of the interfaces is inclined to initiate at the interfacial W-O and the O-O bonds, and the ZrO2(001)/W(001) interfaces are less stable against brittle fracture than bulk W and clean W grain boundaries, which implies that the precipitate of ZrO2 particles may act as the crack initiation sites during stretching. Furthermore, the electronic structures analysis indicates that the interfacial W-O bond has some property of covalent and ionic feature. This work could provide a deep understanding of stability, cohesion and fracture properties of ZrO2/W interfaces.