compositions underwent a liquidliquid phase transition which resulted in glasses 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 experimental error. Clear, brilliant, single-phase glasses were obtained from La 3 Al 5 O 12 , ErLaYAl 5 O 12 , and compositions containing >5 mol% La 2 O 3 substituted for the other rare-earth oxides. Formation of two glasses is attributed to nucleation and growth of the second liquid at a temperature below the equilibrium liquid-liquid transition temperature. Addition of lanthanum depresses the phase transition temperature below the glass transition temperature and the liquidliquid phase transition is not observed. The results are discussed in the context of first-order liquid-liquid phase transitions (polyamorphism) and formation of single-phase glass from liquids that contain a high proportion of 4-coordinate aluminum ions.

Containerless conditions allow well-controlled investigation of liquids at high temperatures. Levitation methods used for this purpose are reviewed, and their application is illustrated by discussion of the properties and behavior of deeply undercooled yttriumaluminum-oxide melts.

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Single-phase glasses containing 37.5 mol% Y 2 O 3 , 7 mol% La 2 O 3 , and 1 mol% Pr, Ho, Nd, Er, Sm, Tm, Eu, or Yb oxide substituted for part of the Y 2 O 3 were synthesized by containerless melting. The spectral transmission and absorption cross sections of the glasses were determined at wavelengths from 360 to 3300 nm. The electronic transitions were broadened compared with results obtained in a crystalline yttrium aluminum garnet (YAG) host. The infrared transmission of the host glass extended to 6000 nm. The optical and physicochemical properties of these glasses are well suited for optical device applications. † Balance is Al 2 O 3 in all cases. ‡ Equivalent to 3.1 ϫ 10 20 Re 3ϩ ions/cm 3 . § Two-phase glass.

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