Effect of Yb₂O₃ additive on transformation behavior of anatase for TiO₂/(O′ + β′)-Sialon multi phase ceramics

TiO₂/(O′ + β′)-Sialon multiphase ceramics were prepared with nano TiO₂ (anatase) powder and (O′ + β′)-Sialon powder as raw materials. Effect of Yb₂O₃ additive on transformation behavior of anatase for TiO₂/(O′ + β′)-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb₂O₃ has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb₂O₃ addition. There exist two forms of the added Yb₂O₃: some enters TiO₂ lattice and the other deposits on the surface of TiO₂. The function of Yb₂O₃ on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows: some Ybⁿ⁺ enter TiO₂ lattice and replace Ti⁴⁺, as well as the redox reaction between Yb³⁺ and TiO₂, which promote the transformation, whereas other Yb₂O₃ deposits on the surface of TiO₂, and Ti-O-Yb bond is formed by the coaction of Yb³⁺ and TiO₂, which inhibit the process.