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

The combustion method has been employed to produce homogeneous, single phased 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 than 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 these powders in catalysis, crystallite size, surface area and porosity measurements 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 pronounced 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) 1998 Kluwer Academic Publishers.