Amorphous precursors of the ZrO2-Fe2O3 system at the ZrO2-rich side of the
concentration range were prepared by co-precipitation of the corresponding
nitrates from aqueous solutions. The thermal behavior of the amorphous samp
les obtained was investigated using differential thermal analysis. It was f
ound that amorphous precursors with Fe2O3 content up to 30 mol% are single
co-gels. In situ phase development during the calcination of the samples at
low air pressure (similar to 4, 10(-3) Pa) was investigated using X-ray di
ffraction at high temperature. The results were compared with the results o
f phase analysis after calcination and cooling in the presence of air at at
mospheric pressure (similar to 10(5) Pa). The phase compositions of the sam
ples at room temperature were determined using X-ray diffraction and laser
Raman spectroscopy. The incorporation of Fe3+ cations partially stabilized
cubic ZrO2 during the calcination in the presence of air at atmospheric pre
ssure, but destabilized this polymorph during calcination at very low press
ure. The observed differences in the phase development were attributed to t
he influence of oxygen vacancies introduced during calcination at very low
pressure. The solubility of Fe2O, in ZrO2 also depended on the calcination
procedure. During calcination at atmospheric pressure, the solubility limit
s of Fe2O3 in ZrO2 decreased from more than 30 mol% at 600 degrees C to sim
ilar to 2mol% at 1100 degrees C. On the other hand, the solubility of Fe2O3
in ZrO2 was shown to be significantly higher during calcination at up to 1
200 degrees C at very low pressure. (C) 2000 Elsevier Science S.A. All righ
ts reserved.