Low-temperature direct synthesis of nanoparticles of fluorite-type ceria-zirconia solid solutions by forced cohydrolysis at 100°C

Nanometer-sized particles ranging from 2 to 3 nm of CeO2 (ceria)-ZrO2 (zirconia) solid solutions with cubic and/or tetragonal fluorite-type structure in the wide composition range from 20 to 100 mol% CeO2, without a trace of monoclinic ZrO2 phase, could be directly synthesized at low temperature of 100 degreesC from acidic aqueous solutions of ZrOCl2 and (NH4)(2)Ce(NO3)(6) by forced simultaneous hydrolysis, i.e., forced cohydrolysis. Analytical values of CeO2/ZrO2 ratio in the as-precipitated solid solutions showed fairly good agreement with starting compositions in the solutions. The proceeding of the hydrolysis and formation rate of fluorite-type solid solutions tended to slow down at near median composition, Any change in crystalline phase of as-precipitated solid solutions was not observed by powder X-ray diffractometry after heat treatment in air below 1000 degreesC, Ceria-zirconia solid solutions with fluorite structures containing large amount of ZrO2 maintained high surface area after heat treatment at 1000 degreesC. (C) 2001 Academic Press.