Combustion synthesis, powder characteristics and crystal structure of phases in Ce-Pr-O system

The combustion method has been employed to produce homogeneous, single phas ed mixed rare-earth oxides in Ce1 - xPrxO2 - y system for x ranging from 0 to 0.7. A cubic fluorite structure is formed for the compositions 0 less th an or equal to x less than or equal to 0.7, while for x > 0.7 mixed phases are obtained. The mixed oxides are formed at the furnace temperature of 500 degrees C in a short duration of 10 min. In view of the importance of thes e powders in catalysis, crystallite size, surface area and porosity measure ments have been carried out. The crystallite size of the powders increases with x while the surface area decreases. As the temperature is increased to 850 degrees C, the surface area decreases and the effect is much pronounce d in cerium rich oxides. The powders on calcination above 900 degrees C in air results in the demixing of Ce and Pr to give two fluorite phases. (C) 1 998 Kluwer Academic Publishers.