THERMOSTABILITY OF CERIA TEXTURE .2. INFL UENCE OF WATER-VAPOR, OXYGEN AND SI-4-3+ DOPANTS( AND AL)

The kinetic study of the textural evolution of a cerium dioxide powder has been achieved by considering separately each process: microporosi ty loss and cristallite size increase. The effect of the water vapour and oxygen content in the calcination atmosphere has been experimental ly obtained for each of these two processes. Water vapour was found to enhance the microporous surface area loss. The experimental specific kinetic rate was in agreement with a mechanism based on the diffusion of hydroxyl ions. Oxygen was found to inhibit the cristallite size inc rease since the experimental kinetic rate varied as P-O2(-1/6). This w as in agreement with a mechanism based on oxygen diffusion. The additi on of Si4+ and Al3+ considerably inhibited the loss in microporous sur face area as well as the cristallite size increase.