Glass formation and polyamorphism in rare-earth oxide-aluminum oxide compositions

We report formation of single- and two phase glasses from rare-earth oxide- alumina materials. Liquids with the Y(3)AI(5)O(12) and Er(3)AI(5)O(12) comp ositions underwent a liquid-liquid phase transition which resulted in glass es with a cloudy appearance due to spheroids of one glass in a matrix of a second glass. The two glasses were isocompositional within the limits of ex perimental error, Clear, brilliant, single-phase glasses were obtained from La(3)AI(5)O(12), ErLaYAI(5)O(12), and compositions containing greater than or equal to 5 mol% La2O3 substituted for the other rare-earth oxides. Form ation of two glasses is attributed to nucleation and growth of the second l iquid at a temperature below the equilibrium liquid-liquid transition tempe rature. Addition of lanthanum depresses the phase transition temperature be low the glass transition temperature and the liquid-liquid phase transition is not observed. The results are discussed in the context of first-order l iquid-liquid please transitions (polyamorphism) and formation of single-pha se glass from liquids that contain a high proportion of 4-coordinate alumin um ions.