Possible cluster models of the intergranular interfaces phase for SiO2/ZrO2 binary oxides were optimized by the density-functional theory (DFT/B3LYP). New results on the formation of the interfacial ring-like Si-O-Zr bonds are validated by the analyses of reaction Gibbs free energies and computational infrared vibration spectra. Moreover, the Mulliken charge population of interfacial Si-O-Zr structures shows that the increased temperature and critical size of the tetragonal-to-monoclinic phase transformation for SiO2-doped ZrO2 mainly come from the reduced charge of oxygen atoms located at the interface and coordinated with the neighboring zirconium atoms, which accords well with the previous theoretical results.