In-situ observation and analysis of solid-state diffusion and liquid migration in a crystal growth system: A segregation-driven diffusion couple

Anton S. Tremsin, Didier Perrodin, Adrian S. Losko, Sven C. Vogel, Takenao Shinohara, Kenichi Oikawa, Gregory A. Bizarri, Edith D. Bourret, Jeffrey H. Peterson, Kerry P. Wang, Jeffrey J. Derby

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Abstract

Energy-resolved neutron imaging is employed for in-situ measurements of dopant transport in a simple experiment performed before the crystal growth of the scintillator BaBrCl:5%Eu via a vertical gradient freeze technique. During a stabilization period preceding growth, we observed the diffusion of Eu from the solid phase into the melt over a period of approximately 4 h. Comparing the measured centerline concentration profile with a mathematical model for the system, we estimate the solid-state diffusivity of Eu in BaBrCl as D1=1.9×10−10 m2/s and an upper limit for the liquid-phase diffusivity of Eu in the melt as D2 *=2.5×10−10 m2/s, at temperatures near the melting point. We compare this experiment, where diffusion is driven by a concentration discontinuity arising from segregation, to the classical diffusion couple technique. Suggestions are offered on how this segregation-driven couple might be improved as a tool for measuring diffusion coefficients, and we draw attention to the great promise of neutron imaging for in-situ measurements of the distribution of elements, with sufficiently high neutron attenuation coefficients, in difficult environments.

Original languageEnglish (US)
Pages (from-to)434-442
Number of pages9
JournalActa Materialia
Volume186
DOIs
StatePublished - Mar 2020

Keywords

  • Diffusion
  • Modeling
  • Neutron imaging
  • Segregation
  • Solid/liquid interface

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    Tremsin, A. S., Perrodin, D., Losko, A. S., Vogel, S. C., Shinohara, T., Oikawa, K., Bizarri, G. A., Bourret, E. D., Peterson, J. H., Wang, K. P., & Derby, J. J. (2020). In-situ observation and analysis of solid-state diffusion and liquid migration in a crystal growth system: A segregation-driven diffusion couple. Acta Materialia, 186, 434-442. https://doi.org/10.1016/j.actamat.2020.01.013