Studies of the Systems Al<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub> and Na<sub>2</sub>O-ZrO<sub>2</sub>

Abstract

From the ceramic point of view the systems Al2O3-ZrO2 and Na2O-ZrO2 were studied. The results show that in the system Al2O3-ZrO2 there exists no compound as well as solid solution, and that a eutectic point is 1890°±5°C at the composition 45% Al2O3, 55% ZrO2.The rate of the growth of Al2O3 crystals is the highest at 80% Al2O3⋅20% ZrO3, and in this case, the transformation of ZrO2 from high to low temperature modification is kept in check most efficiently.In the system Na2O-ZrO2 there is a compound Na2O⋅ZrO2, and its temperature of formation is lower than the decomposition temperature of Na2CO3.The rate of reaction is expressed by{1-(1-α)1/3}2=-0.3715+0.0023tin which α is the rate of formation, and t is time. This compound melts incongluently at about 1180°C in which the quantity decomposed may be expressed by a logarithmic function of time.In Na2O-ZrO2 system the vapour pressure of Na2O which does not take part of the formation of compound is so large that it makes impossible to draw a melting curve.