High- and Low-Density Glasses and Liquids in the Yttrium Oxide - Aluminum Oxide System

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9818133 McMillan This project aims to study liquids and amorphous solids in the technologically important system yttrium oxide - aluminum oxide. The work involves fully characterizing a new type of liquid-liquid phase transition between two liquid phases with the same composition, but with different densities and other thermodynamic properties. Spectroscopic methods will be utilized to study the structural nature of the glasses, as well as the mechanical and thermodynamic properties of the supercooled liquids and glasses. A range of Y203-A1203 compositions prepared by quenching or annealing at different controlled rates. Techniques of sol-gel synthesis, rapid roller quenching, and aerodynamic levitation, will be combined to make samples of low- and high-density glassy materials. The liquid-liquid phase transition causes an unusually large viscosity change throughout the glass-forming range, which greatly affects the fiber-pulling characteristics of yttria-alumina liquids. This property is under intense study by an industrial group (Containerless Research Inc.), who have commercial applications for the ceramic fibers. These have been shown to possess high tensile strength, are compatible with alumina at high temperature, and exhibit excellent creep resistance. Collaboration with the CRI group was initiated during our prior NSF Selected Grant for Exploratory Research award. CRI will continue to supply samples for structural characterization. The spectroscopic and calorimetric studies to be carried out under the present award will permit understanding of the structural nature of the low- and high-density liquids and glasses and their properties. This study is relevant to the crystallization behaviour of the laser host crystal yttrium aluminium garnet (YAG). The graduate student and post-doctoral associate involved in the project will benefit from working on this scientifically and technologically important problem, in close contact with the CRI industrial group during the collaborative phase of this project.%%%These studies on yttrium oxide - aluminum oxide glassy systems are relevant not only to the crystallization behavior of the laser host crystal YAG, but also to the formation of fibres pulled from undercooled melts in these systems. The project has significant potential for optimizing the processing of materials used in fiber-optics data transmission.