Effect of CeO ₂ addition on the sintering behavior of the alumina‐rich calcium aluminate ceramics

Abstract In this work, the CaAl ₄ O ₇ ceramics and CaAl ₁₂ O ₁₉ ceramics were fabricated by the solid‐state sintering technology and the effects of CeO ₂ 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 CaAl ₄ O ₇ ceramics and CaAl ₁₂ O ₁₉ ceramics increased about 23.8% and 24.2% after adding 3.0 wt% of CeO ₂ than that of the samples without additives. Meanwhile, an increase in lattice parameters occurred in the CaAl ₄ O ₇ ceramics and CaAl ₁₂ O ₁₉ ceramics. The CeO ₂ could form the solid solution in the CaAl ₄ O ₇ ceramics, inducing the lattice distortion and the activation of the lattice. The Ce ⁴⁺ in CeO ₂ could be dissolved in the structure of CaAl ₁₂ O ₁₉ 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 CaAl ₄ O ₇ ceramics and CaAl ₁₂ O ₁₉ ceramics and improve their sinterability. Moreover, a considerable increase in bulk density occurred in both CaAl ₄ O ₇ ceramics and CaAl ₁₂ O ₁₉ ceramics with increasing sintering temperatures due to the greater densification obtained from the enhanced mass transport at elevated temperatures.