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Ritter K.,Jena University Fraunhoferstr 6 | Gerlach S.,Jena University Fraunhoferstr 6 | Russel C.,Jena University Fraunhoferstr 6
Journal of Non-Crystalline Solids | Year: 2010

Glasses in the system Na2O/K2O/CaO/CaF 2/Al2O3/SiO2 were doped with Ag 2O, CeO2 and Sb2O3. They were irradiated with UV light and subsequently thermally annealed at 530 °C, a temperature just above Tg. This led to a slight yellow coloration. A second thermal annealing step was carried out at a temperature of 560 °C. This led to the crystallization of cubic CaF2 as proved by X-ray diffraction. The crystallization was only observed at that side, the sample was irradiated. Samples, annealed in a two step process at 530 °C for 1 h and 560 °C for 20 h without previous irradiation did not show crystallization. As shown by scanning electron microscopy, the size of the crystals was 30 nm. If this procedure was carried out in glass slides with a thickness of 0.5 mm, bended samples were obtained. This is due to a volume expansion which runs parallel to the crystallization. © 2010 Elsevier B.V. All rights reserved. Source

Kracker M.,Jena University Fraunhoferstr 6 | Worsch C.,Jena University Fraunhoferstr 6 | Russel C.,Jena University Fraunhoferstr 6
Journal of Nanoparticle Research | Year: 2013

Thin layers of palladium with a thickness of 5 nm were sputtered on fused silica substrates. Subsequently, the coated glasses were annealed at a temperature of 900 C for 1 h. This resulted in the formation of small and well-separated palladium nanoparticles with diameters in the range from 20 to 200 nm on the glass surface. The existence of a palladium oxide layer can be detected using optical absorption spectroscopy. Purging with hydrogen leads to an irreversible change in the optical spectra due to the reduction of PdO to metallic palladium. Changing the gas atmosphere from hydrogen to argon leads to significant reversible changes in the optical properties of the particle layer. Based on Mie theory and the respective dielectric functions, the spectra were calculated using the real particle size distribution, weighted dispersions relation to adapt the geometrical conditions and complex dielectric functions of palladium and palladium hydride. A good agreement with measured spectra was found and the dependency of the surrounding media can be explained. Graphical Abstract: [Figure not available: see fulltext.] © 2013 Springer Science+Business Media Dordrecht. Source

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