A density functional theory study on the interfacial bonding properties of SiO2 ceramic and Ag(Ti) filler metal

Ti is a very important active element in brazing SiO2 ceramics by using Ag-based fillers. Therefore, a density functional theory (DFT) study was applied to investigate the influence of Ti dopant on the interfacial bonding properties of the SiO2 ceramic/Ag interface. Firstly, we built SiO2(0001)/Ag(111) interface with very small lattice misfit. The interface structure with O1 termination and hollow site was found to have maximum value of work of adhesion (Wad). Then, the Ti atoms were doped into the interface at different locations to simulate the possible diffusion sites. The energy results show that Ti atom in the Ag slab was more likely to move to the interface and form bonding with O atoms. The result supports the interface structure of SiO2/Ti-O compounds/Ag. When the coverage of Ti atoms at the interface was raised to 100%, Wad of the interface can reach as large as 16.34 J/m2. The electronic structure analysis indicates that Ti atom at interface can form strong ionic bonding with O atoms. With the increase of Ti atoms, the single Ti-O bonding is weakened with less charge transfer. However, the number of Ti-O bonding increases and the interfaces are strengthened further.