Low cation coordination in oxide melts.
The complete set of partial pair distribution functions for a rare earth oxide liquid are measured by combining aerodynamic levitation, neutron and x-ray diffraction on Y2O3, and Ho2O3 melts at 2870 K. The average Y-O (or Ho-O) coordination of these isomorphic melts is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2O3 (or Ho2O3). Investigation of La2O3, ZrO2, and Al2O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation-oxygen coordination. These measurements suggest a general trend towards lower coordination compared to their crystalline counterparts. It is found that the coordination drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations, such as SiO2. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.
Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100, USA and X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA and Materials Development Inc., Arlington Heights, Illinois 60004, USA.
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Skinner
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
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Benmore
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA and Materials Development Inc., Arlington Heights, Illinois 60004, USA.
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Weber
Materials Science & Engineering, University of North Texas, Denton, Texas 76203, USA.
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Du
Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Neuefeind
Materials Development Inc., Arlington Heights, Illinois 60004, USA.
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Tumber
Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100, USA.
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Parise