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Zirconia has many excellent properties, such as high melting point, high hardness, highstrength and chemical stability etc, and its phase transformation toughening mechanism canimprove the thermal shock resistance. Zirconia is widely used in the refractory field due to itsexcellent properties, for example, ZrO2-C refractories are the best alternative as slag line of castgate. Usually, the CaO stabilized zirconia is used as the mainly raw material. However, CaOprecipitated from the lattice of zirconia results in destabilization of zirconia phase when thezirconia contacts with the protective slag, which is considered as the main reason of the damageof the refractories. Therefore, to improve the properties of ZrO2-C refractories, the in-depth studyof the stability of zirconia materials is very important and interesting.In this paper, CaO stabilized zirconia, CaO-Y2O3 stabilized zirconia, MgO stabilizedzirconia and Y2O3 stabilized zirconia were selected as research objects. The reactions betweenthe four kinds of zirconia and the Al2O3, SiO2, Fe3O4 and MnO2 in slag, and the stability of thefour zirconia in slag with different basicity at high temperature, were investigated through XRD,SEM and EDS, etc. And the mechanism of losing stability of zirconia was analyzed. The mainconclusions are as follows:1) Minor Al2O3 can solute into the lattice of zirconia, but redundant Al2O3 will react withCaO stabilized zirconia, CaO-Y2O3 stabilized zirconia and MgO stabilized zirconia, respectively,which result in the losing stability of partially zirconia; SiO2 reacts easily with the stabilizer inCaO stabilized zirconia, CaO-Y2O3 stabilized zirconia and MgO stabilized zirconia at 1600℃,which result in the losing stability of partially zirconia; Fe3O4 reacts with MgO in MgOstabilized zirconia, resulting in the losing of stability, but reacts with the stabilizers in CaOstabilized zirconia, CaO-Y2O3 stabilized zirconia and Y2O3 stabilized zirconia, resulting theincreasing of stability; MnO2 can increase the stabilities of the four kinds of zirconia.2) The reaction of the oxides in slag and the stabilizers in four zirconia determines the effectof protective slag on the stability of zirconia. The reaction of Al2O3, SiO2 in slag with CaOstabilized zirconia, CaO-Y2O3 stabilized zirconia and MgO stabilized zirconia results in thelosing of zirconia; increasing the basicity of slag can increase the stability of zirconia.Considering all the results, the stability of zirconia stabilized by Y2O3 is the best.
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