Influence of heat treatment on crystal size of active oxides

Pechini method was used to prepare the nano-phased active oxides,in which RuO2,IrO2 and PdO were the main components.Mono-phased oxides can be obtained when suitable temperatures are selected.Heat treatment has great effects on crystal size of RuO2,IrO2 and PdO.Though the size increases with temperature,there is not a simple incremental relationship between the temperature and the crystal size.The two-staged increment in the preparing processes is observed for the three active oxides during heat treatment.The crystal size grows up rapidly at temperature lower than Tc,which is the intersection temperature between the two-staged increment lines,and grows up slowly at temperature higher than Tc.It implies that the two-staged increment of crystal size with increase of temperature is a special phenomenon for precious element systems.According to the two-staged phenomena,it is suggested that the equation D = bT + a,in which the constants are obtained by curve fitting based on experiment,is helpful in the industrial processes to control the sizes of the three active oxides.