Co-precipitation and Sol-gel Method

The sol-gel method is used to produce clean, non-stoichiometric, dense, equidi-mensional, and monodisperse particles of simple oxides such as T1O2 and Si02 [128]. This observation unfortunately cannot be extended to the complex oxides and ferrites in particular. In most general case, the resulting particles obtained agglomerate. 

The nanosize powders of CoFe204 (average particle size 30 nm) [129] and NiFc204 (5-30 nm) [130] do not change their grains sizes even after annealing at temperatures 450 and 400 °C, respectively. The sol-gel method is the main synthesis technique for cobalt ferrite doped with Mn [131], Cr [132], Bi [133], Y, La [134], Gd, Nd [135] and Zn [136]. The sol-gel method has been very attractive 

The hybrid materials such as oxide/polymer nanocomposites can be prepared by this method. For example, the nanoscale heterogeneity can be of controlled size in metal/ceramic nanocomposites. The reduction of metal-oxides with hydrogen gives nanocomposite powders such as Fe core in the silicon oxide or Fe203 [147] and NiFc204 shell [148]. Metal particles of several nanometers size with narrow size distribution are statistically distributed in the oxide matrix without any agglomerates, as a result of binding the metal complex to oxide matrix. The narrow particle size distribution cannot be obtained if complexion of ions appears (Table 5.6). 

---

Schwartz, R. W. 1989. Chemical processing of PbTi03 by co-precipitation and sol-gel methods the role of powder and gel characteristics on crystallization behavior. PhD dissertation. University of Illinois at Urbana-Champaign. 

To evaluate differences in the reactivity of a series of cobalt containing perovskite type catalysts for the CO oxidation reaction, a "single path" preparation route is desirable. Two such routes were tested using three precursors of BaCoOa, LaCo03 and BaaCoWOs namely co-precipitation and sol-gel methods. 

---