Crystallization of BaF2from droplets of phase separated glass-evidence of a core-shell structure by ASAXS

Armin Hoell, Vikram Singh Raghuwanshi, Christian Bocker, Andreas Herrmann, Christian Rüssel, Thomas Höche

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Glasses with the mol% compositions 1.88 Na2O·15.04 K2O·7.52 Al2O3·69.56 SiO2·6.00 BaF2 and 1.88 Na2O·15.03 K2O·7.52 Al2O3·69.52 SiO2·6.00 BaF2·0.05 SmF3 were studied using X-ray diffraction, transmission electron microscopy, and anomalous small-angle X-ray scattering (ASAXS). While the glass doped with samarium showed liquid/liquid phase separation of droplets with sizes of around 100 nm, the glass without samarium did not. The samples were annealed at 580 °C or at 600 °C which led to the crystallization of cubic BaF2. The X-ray diffraction patterns showed strongly broadened lines. Hence, the BaF2 crystals possess sizes in the nm range. ASAXS gave evidence of a core shell structure. In agreement with earlier studies, it is assumed that the shell acts as a diffusion barrier that hinders crystal growth. Surprisingly, the cores and shells from the crystallization of the homogeneous glass and from the second glass, which is Sm-doped and shows liquid/liquid phase separation, both possess similar dimensions, even though the origin of the barrier is very different. The doped samples show long luminescence lifetimes of nearly 5 ms at a wavelength of 600 nm, which is nearly as long as those in fluoride phosphate glasses. This journal is

Original languageEnglish
Pages (from-to)5031-5039
Number of pages9
JournalCrystEngComm
Volume22
Issue number30
DOIs
Publication statusPublished - 14 Aug 2020
Externally publishedYes

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