Fraunhofer-Gesellschaft

Publica

Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Surface and bulk crystallization of Ba1-xSrxZn2Si2O7 from glasses in the system BaO/SrO/ZnO/SiO2 doped with Nb2O5 or Ta2O5

 
: Heitmann, S.; Thieme, K.; Thieme, C.; Kracker, M.; Höche, T.; Rüssel, C.

:

Ceramics international : CI 45 (2019), No.6, pp.7580-7587
ISSN: 0272-8842
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
03VP01701
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
03VP01702
English
Journal Article
Fraunhofer IMWS ()

Abstract
Stoichiometric 0.5 BaO·0.5 SrO·2 ZnO·2 SiO2 glass was doped with 5 mol% Nb2O5 or Ta2O5. The effect of these additives on the crystallization behavior was studied using thermal analyses, X-ray diffraction, as well as scanning electron microscopy including elemental analyses. The addition of Nb2O5 or Ta2O5 significantly increases the glass stability enabling the preparation of crystal-free BaO·SrO·ZnO·SiO2 glasses with almost stoichiometric composition. Besides the desired main crystal phase Ba1-xSrxZn2Si2O7, also alkaline earth tantalates and niobates as well as Zn2SiO4 are observed. The Nb-containing glass shows solely surface crystallization, whereas in the Ta-containing glass, additionally numerous barium tantalate crystals precipitate in the bulk acting as seeds for the nucleation of Ba1-xSrxZn2Si2O7. If the surface crystallized layer of Ba1-xSrxZn2Si2O7 approaches such a barium tantalate crystal or gets close to it, then the crystallization of Ba1-xSrxZn2Si2O7 is initiated. It is supposed that these nucleation processes are notably facilitated by the stresses present in these glass-ceramics.

: http://publica.fraunhofer.de/documents/N-549240.html