El. Uzunova et al., SYNTHESIS OF NANO-DIMENSIONAL IRON-COBALT SPINEL MIXED OXIDES FROM LAYERED-TYPE CARBONATE HYDROXIDE PRECURSORS, Bulletin of the Chemical Society of Japan, 70(8), 1997, pp. 1985-1993
Pyroaurite-like carbonate hydroxide precursors Co1-xFex(CO3)(x/2)(OH)(
2) . nH(2)O, where x varies in the range 0.25 less than or equal to x
less than or equal to 0.75, yield cation deficient mixed oxides with p
article dimensions in the nano-scale range. The thermal decomposition
and spinel structure formation processes have been studied by thermal
analysis and IR spectroscopy, revealing an intermediate of hydroxide o
xide type. Mesoporous mixed oxides with cubic spinel structure were sy
nthesised at 300-400 degrees C with significant contribution of small
pores of radii < 200 Angstrom. Oxygen desorption from cobalt ferrite,
synthesised at 350 degrees C, suggests the existence of a high content
of extraframework oxygen. The temperature-programmed reduction (TPR)
with hydrogen occurs in one stage for all cobalt/iron compositions. Th
e peak maxima shift to higher temperatures and a broadening is observe
d with increasing the iron content. Partly inverse cation distribution
s of the spinel ferrites are deduced from the Moessbauer spectra.