The effect of long-term firing at 2100–2200°C on the concentration and microstructure of solid solutions in the systems ZrO2-Y2O3-CaO and ZrO2-Y2O3-MgO

Conclusions Solid solutions in the system ZrO₂-MgO fired at a high temperature (above 2000°C) in vacuo (5 · 10^–4mm Hg) for 5 h decompose as a result of the complete vaporization of the MgO. Solid solutions of ZrO₂-CaO undergo partial decomposition when fired in these conditions. The addition of 2 mole % or more yttrium oxide to the solid solutions ZrO₂-CaO and ZrO₂-MgO results in significantly lower CaO and MgO vaporization.The long-term exposure of solid solutions in the system ZrO₂-CaO and ZrO₂-MgO to 2200°C in a helium atmosphere results in the formation of an intercrystalline layer in which not only the stabilizing oxide but also the impurities are concentrated.In three-component solid solutions which contain yttrium oxide the degree of vaporization is lower and the intergranular secondary phase less developed so that the degree of collective recrystallization is lower.Translated from Ogneupory, No. 8, pp. 44–48, August, 1976.