Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Glasses and Glass Transition I (jointly with DY, DF)

CPP 30.9: Talk

Wednesday, March 16, 2011, 12:15–12:30, KÖN Farb

Structural investigations on Eu-doped fluorobromozirconate glass ceramics. — •Marie-Christin Wiegand¹, Bernd Ahrens², Bastian Henke^2,3, and Stefan Schweizer^2,3 — ¹Department of Physics, University of Paderborn, Warburger Str. 100, 33100 Paderborn, Germany — ²Fraunhofer Center for Silicon Photovoltaics, Walter-Hülse-Str. 1, 06120 Halle (Saale), Germany — ³Centre for Innovation Competence SiLi-nano^®, Martin Luther University of Halle-Wittenberg, Karl-Freiherr-von-Fritsch-Str. 3, 06120 Halle (Saale), Germany

Modified Eu-doped fluorozirconate glasses are regarded as promising materials for photovoltaic and medical applications. In these glasses, a substantial fraction of the fluorine ions was replaced by bromine ions resulting in the formation of BaBr₂ nanocrystals upon subsequent thermal treatment of the as-made glass. Interestingly, the metastable hexagonal phase of BaBr₂ is always formed first before further annealing leads to the formation of orthorhombic phase BaBr₂, i.e., a phase transition from hexagonal to orthorhombic phase BaBr₂ occurs upon annealing. During the annealing a part of the doped Eu²⁺ is incorporated into the BaBr₂ nanocrystals enabling fluorescent transitions of Eu²⁺ in hexagonal and orthorhombic BaBr₂, respectively, upon ultraviolet excitation. The nanocrystal size and the structural phase depend on the addition of InF₃ and YF₃ and on the Br/(F+Br)-ratio, which was investigated by differential scanning calorimetry and x-ray diffraction. In addition, photoluminescence experiments were performed to monitor the phase transition by optical means.