npj Microgravity (Mar 2024)

Microgravity effects on nonequilibrium melt processing of neodymium titanate: thermophysical properties, atomic structure, glass formation and crystallization

  • Stephen K. Wilke,
  • Abdulrahman Al-Rubkhi,
  • Chihiro Koyama,
  • Takehiko Ishikawa,
  • Hirohisa Oda,
  • Brian Topper,
  • Elizabeth M. Tsekrekas,
  • Doris Möncke,
  • Oliver L. G. Alderman,
  • Vrishank Menon,
  • Jared Rafferty,
  • Emma Clark,
  • Alan L. Kastengren,
  • Chris J. Benmore,
  • Jan Ilavsky,
  • Jörg Neuefeind,
  • Shinji Kohara,
  • Michael SanSoucie,
  • Brandon Phillips,
  • Richard Weber

DOI
https://doi.org/10.1038/s41526-024-00371-x
Journal volume & issue
Vol. 10, no. 1
pp. 1 – 11

Abstract

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Abstract The relationships between materials processing and structure can vary between terrestrial and reduced gravity environments. As one case study, we compare the nonequilibrium melt processing of a rare-earth titanate, nominally 83TiO2-17Nd2O3, and the structure of its glassy and crystalline products. Density and thermal expansion for the liquid, supercooled liquid, and glass are measured over 300–1850 °C using the Electrostatic Levitation Furnace (ELF) in microgravity, and two replicate density measurements were reproducible to within 0.4%. Cooling rates in ELF are 40–110 °C s−1 lower than those in a terrestrial aerodynamic levitator due to the absence of forced convection. X-ray/neutron total scattering and Raman spectroscopy indicate that glasses processed on Earth and in microgravity exhibit similar atomic structures, with only subtle differences that are consistent with compositional variations of ~2 mol. % Nd2O3. The glass atomic network contains a mixture of corner- and edge-sharing Ti-O polyhedra, and the fraction of edge-sharing arrangements decreases with increasing Nd2O3 content. X-ray tomography and electron microscopy of crystalline products reveal substantial differences in microstructure, grain size, and crystalline phases, which arise from differences in the melt processes.