000K  utf8
0100  176091228X
1100  2020$c2020-06-29
1500  eng
2051  10.1039/C9CE02003A
3000  Hoell, Armin
3010  Bocker, Christian
3010  Herrmann, Andreas
3010  Höche, Thomas
3010  Raghuwanshi, Vikram Singh
3010  Rüssel, Christian
4000  Crystallization of BaF2 from droplets of phase separated glass - evidence of a core-shell structure by ASAXS  [Hoell, Armin]
4060  9 Seiten
4209  Glasses with the mol% compositions 1.88 Na2O·15.04 K2O·7.52 Al2O3·69.56 SiO2·6.00 BaF2 and 1.88 Na2O·15.03 K2O·7.52 Al2O3·69.52 SiO2·6.00 BaF2·0.05 SmF3 were studied using X-ray diffraction, transmission electron microscopy, and anomalous small-angle X-ray scattering (ASAXS). While the glass doped with samarium showed liquid/liquid phase separation of droplets with sizes of around 100 nm, the glass without samarium did not. The samples were annealed at 580 °C or at 600 °C which led to the crystallization of cubic BaF2. The X-ray diffraction patterns showed strongly broadened lines. Hence, the BaF2 crystals possess sizes in the nm range. ASAXS gave evidence of a core shell structure. In agreement with earlier studies, it is assumed that the shell acts as a diffusion barrier that hinders crystal growth. Surprisingly, the cores and shells from the crystallization of the homogeneous glass and from the second glass, which is Sm-doped and shows liquid/liquid phase separation, both possess similar dimensions, even though the origin of the barrier is very different. The doped samples show long luminescence lifetimes of nearly 5 ms at a wavelength of 600 nm, which is nearly as long as those in fluoride phosphate glasses.
4950  https://doi.org/10.1039/C9CE02003A$xR$3Volltext$534
4961  http://uri.gbv.de/document/gvk:ppn:176091228X
5051  540