Abstract

Combining small angle and wide angle x-ray scattering with aerodynamic levitation techniques has enabled in situ detection of phase transitions in the liquid state under contactless conditions1. At very high temperatures yttria-alumina melts show a first order transition, previously inferred from phase separation in quenched glasses. We show how the transition coincides with a narrow and reversible maximum in SAXS indicative of liquid unmixing on the nanoscale combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions – a polyamorphic rotor – from which the reversible changes in molar volume and entropy can be estimated. These results have important implications for the nature of phase transitions in other liquids and glasses.

1 Detection of First Order Liquid-Liquid Phase Transitions in Yttrium Oxide – Aluminium Oxide Melts. G.N. Greaves, M.C. Wilding, S. Fearn, D. Langstaff, F. Kargl, S. Cox, O. Majérus, Q. Vu Van, C.J. Benmore, R. Weber, C.M. Martin, L. Hennet, Science in press 2008.