Effect of CeO2 addition on the sintering behavior of the alumina-rich calcium aluminate ceramics

In this work, the CaAl₄O₇ ceramics and CaAl₁₂O₁₉ ceramics were fabricated by the solid-state sintering technology and the effects of CeO₂ as the additive on their sintering behavior subjected to sintering at temperatures of 1500°C, 1550°C, and 1600°C were investigated. It was demonstrated that the bulk densities of the CaAl₄O₇ ceramics and CaAl₁₂O₁₉ ceramics increased about 23.8% and 24.2% after adding 3.0 wt% of CeO₂ than that of the samples without additives. Meanwhile, an increase in lattice parameters occurred in the CaAl₄O₇ ceramics and CaAl₁₂O₁₉ ceramics. The CeO₂ could form the solid solution in the CaAl₄O₇ ceramics, inducing the lattice distortion and the activation of the lattice. The Ce⁴⁺ in CeO₂ could be dissolved in the structure of CaAl₁₂O₁₉ phase and result in the structural defects, which would accelerate ion exchange and promote the in situ reaction of synthetic products. These behaviors could promote the sintering process of the CaAl₄O₇ ceramics and CaAl₁₂O₁₉ ceramics and improve their sinterability. Moreover, a considerable increase in bulk density occurred in both CaAl₄O₇ ceramics and CaAl₁₂O₁₉ ceramics with increasing sintering temperatures due to the greater densification obtained from the enhanced mass transport at elevated temperatures.