Abstract
Ternary compound in the CaO-Al2O3-HfO2 system, 13CaO·6Al2O3·2HfO2 (stated by C13A6Hf2 hereafter), was fabricated by melt process using an arc-imaging furnace. This compound has not been reported ever, based on our knowledge. The new phase has similar XRD patterns to the 13Cao·6Al2O3·2ZrO2 (C13A6Z2) phase in the ternary phase diagram CaO-Al2O3-ZrO2. Though Zirconium and Hafnium generally shows similar properties, the reactivity of these two compounds in the solid phase was totally different. The Zirconium compound (C13A6Z2) was fabricated by both solid state reaction (1200°C, 6h) and the melt process, starting from powder mixture of CaCO3, Al2O3, and ZrO2. On the other hand, the Hafnium compound (C13A6Hf 2) was fabricated only by the melt process from powder mixture of CaCO3, Al2O3, and HfO2. The zirconium pure phase was not fabricated by the solid state reaction; it gave three isolated phases, 12CaO·7Al2O3 (C12A7), CaHfO3, and C13A6Hf2. This difference might be caused by a low diffusion rate of Hf ions in the C12A7 structure.
