Structure and properties of YAlO3/NbC heterogeneous nucleation interface: First principles calculation and experimental research

Abstract

The characteristics of YAlO3/NbC heterogeneous nucleation interface are strongly associated with the interfacial structure, electronic construction and properties. The lattice mismatch between low index crystal faces of YAlO3 and NbC was calculated by using the Bramfitt two-dimensional lattice mismatch theory. The work of adhesion, interfacial energy and electronic structure of the YAlO3(001)/NbC(100) interface structures were calculated by the first principles method. The charge density difference, electron localization function and crystal orbits overlap population were adopted to analyze the charge transfer and bond characteristics. The microstructure of surfacing alloy was observed by transmission electron microscopy (TEM). The results show that, the two-dimensional lattice mismatch of YAlO3(001)-NbC(100) interface is 5.4%, which testifies that YAlO3 can meet the lattice structure condition of being an effective heterogeneous nucleus of NbC. In all interface structures, the work of adhesion of C-O2 model is the largest (Wad = 6.558 J/m2) and the interfacial energy of C-Y model is the smallest (γ = 0.54 J/m2). It can be confirmed that the C-Y interface structure is the most stable one, whose interfacial energy is the smallest. The chemical bonds between interface atoms of all models are major covalent bonds and few metal bonds. The calculation results indicate that YAlO3(001) slab and NbC(100) slab can form a stable interface structure. The TEM results verify that the rare earth compound in NbC particle is YAlO3. In addition, NbC growth encircling YAlO3 and they are combined tightly. Therefore, YAlO3 can act as the effective heterogeneous nucleus of NbC and refine it.