Abstract: MgO-CaO refractories have a broad application prospect as furnace lining materials for clean steel and special steel smelting due to their good high temperature resistance and ability to purify steel. However, these materials still have problems such as difficult sintering, easy hydration and mechanical properties need to be improved. In this work, Y₂O₃/ZrO₂ co-doped MgO-CaO refractories were prepared by comparing with Y₂O₃ and ZrO₂ single-doped MgO-CaO refractories. The effect of Y₂O₃/ZrO₂ introduction on the microstructure and properties of materials was investigated. The results show that some Y₂O₃ dissolves into the CaO lattice, while other Y₂O₃ locates at the intergranular region in the Y₂O₃ single-doped MgO-CaO materials. The intergranular Y₂O₃ hinders the sintering of the material. When a small amount of ZrO₂ is synergistically introduced, the density of the material increases, and the room temperature flexural strength and hydration resistance are improved. This is due to the in-situ generated CaZrO₃ filling in the voids, which is favourable to the sintering properties of the materials. However, when excessive ZrO₂ is introduced, more CaZrO₃ generates in the materials, and the significant volume expansion leads to the increase of apparent porosity, leading to a decrease in the mechanical properties and hydration resistance of the materials.

Key words: MgO-CaO refractoy, yttrium oxide, doping, microstructure, hydration resistance