Interaction of cerium oxide with hafnium, zirconium, and yttrium oxides at 1500°C

摘要

Phase relations in the ternary systems HfO{sub}2-Y{sub}2O{sub}3-CeO{sub}2, ZrO{sub}2-Y{sub}2O{sub}3-CeO{sub}2 were studied and phase relations in the binary systems HfO{sub}2-CeO{sub}2, ZrO{sub}2-CeO{sub}2, CeO{sub}2-Y{sub}2O{sub}3 were spec fled at 1500 'Gin air in the whole concentration range. The isothermal sections at 1500°C for the systems HfO{sub}2-Y{sub}2O{sub}3-CeO{sub}2 and ZrO{sub}2-Y{sub}2O{sub}3-CeO{sub}2 were developed. Samples were prepared from nitrate solutions by evaporating, drying, grinding and consequent annealing at 1500°C. X-ray diffraction, petrography and electron microscopy were used for phase analysis. Solid solutions based on C-Y{sub}2O{sub}3, F-CeO{sub}2, F -HfO{sub}2 and ZrO{sub}2 were revealed to form wide phase fields and narrow ones of T-ZrO{sub}2 and M-HfO{sub}2. No ternary compounds were revealed. In the field of fluorite-type solid solutions F-HfO{sub}2(ZrO{sub}2), the isoparametric lines were determined and mechanism of ion substitution was suggested as follows: ions of yttrium and cerium substitute each other without a substantial contribution of zirconium and hafnium ions.