observation and analysis of solid-state diffusion and liquid migration in a crystal growth system; A Segregation-driven diffusion couple

Tremsin, A. S.*; Perrodin, D.*; Losko, A. S.*; Vogel, S. C.*; 篠原 武尚; 及川 健一; Bizarri, G. A.*; Bourret, E. D.*; Peterson, J. H.*; Wang, K. P.*; et al.

Acta Materialia, 186, p.434 - 442, 2020/03

https://doi.org/10.1016/j.actamat.2020.01.013

Energy-resolved neutron imaging is employed for 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 = 1.9 10 m/s and an upper limit for the liquid-phase diffusivity of Eu in the melt as = 2.5 10 m/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.