Effect of iron oxide on the phase composition of zirconia refractories

Conclusions

It has been established that in the compositions ZrO₂∶Y₂O₃∶Fe₂O₃ and ZrO₂∶Nd₂O₃∶Fe₂O₃ the processes of formation of rare earth ferrites and ZrO₂ cubic solid solutions occur simultaneously. At temperatures of up to 1300°C the ferrite-formation process is fastest; with a further increase in the temperature the synthesis of ZrO₂ cubic solid solutions is significantly intensified.

In the mixture of CaO, ZrO₂, and Fe₂O₃, the calcium oxide reacts only with ZrO₂.

The greatest stability in relation to the action of Fe₂O₃ is clearly found in the case of the zirconia-calcium oxide solid solutions.

In the mixtures of cubic solid solutions of Nd₂Zr₂O₇-ZrO₂ or ZrO₂-Y₂O₃ and Fe₂O₃, an interaction is only possible in the case where the synthesis of ferrites is not accompanied by the restructuring of the crystal lattice of ZrO₂, i. e., by destabilization of the material.

The presence of Fe₂O₃ prevents the decomposition of zirconia-calcium oxide and zirconia-neodymium oxide solid solutions under conditions of prolonged heating in air at 1300°C. The zirconia-yttria cubic solid solution is the most stable and does not decompose, regardless of the concentration of Fe₂O₃, after a dwell of 250 h at 1300°C.