Glass - Back to the Future!

Presenting Author:
Yuko Nakatsuka

article posted 17 April 2016

Yuko Nakatsuka is a PhD student of Graduate School of Engineering, Kyoto University, Japan. Her research interests are magnetic and magneto-optical properties of oxide glasses containing transition elements. She received masterís degree in engineering from Kyoto University in March, 2014. Since April 2015, she has been also a JSPS (Japanese Society for the Promotion of Science) Research Fellow (DC2). She was a visiting student at the Laboratory of Glass Science with Prof. Dr. Lothar Wondraczek in Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Germany from March 2015 to February 2016.

Direct Observation of Metallic Iron Nanoclusters in Amorphous Iron-containing Silicate Thin Films

Yuko Nakatsuka*1,2, Sindy Fuhrmann2, Kilian Pollok3, Falko Langenhorst3, Koji Fujita, Shunsuke Murai1, Katsuhisa Tanaka1 Lothar Wondraczek2

The Faraday effect plays an important role in telecommunication or laser technology, as it can be applied to optical devices such as optical isolators and switches. As optical isolators, rare-earth ion containing glasses have been practically used. However, glassy materials have smaller Verdet constant compared to crystalline materials, meaning that it is necessary to prepare a large device, which is not suitable for tiny integrated systems. To overcome the limitation of glassy materials, composite of nanoparticles with glass matrix are proposed to obtain larger Faraday effect (I. Edelman and J. Kliava, Phys. Status Solidi B, 246 (2009) 2216). In this presentation, results from transmission electron microscopy of an amorphous 67.5FeO∑32.5SiO2 thin film are presented that possesses an unusually large Faraday effect as far as a glassy material is concerned. The iron-rich glass was prepared by pulsed laser deposition method on an amorphous silica substrate. Selected area diffraction reveals broad rings typical for glass (2.8 Ň, 1.5 Ň), in addition a somewhat sharper ring with few single sharp spots is present at 2.0 Ň consistent with the (110) lattice spacing of metallic iron. Furthermore, weak spots can be found at 1.44 and 1.18 Ň consistent with body-centered cubic (bcc) iron. Bright field image of both the iron-rich glass and the vitreous silica substrate looks homogeneous, however the former appears grainy indicating slight compositional differences. Dark field images using small portions of the 2 Ň ring locate numerous iron nanoclusters of 1 to 3 nm diameter throughout the iron-rich glass. Single nanocrystals were also directly imaged using high-resolution microscopy. Thus, it is shown that the 67.5FeO∑32.5SiO2 thin film is a composite of metallic iron clusters precipitated in an iron silicate glass matrix.

1 Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
2 Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena, Germany
3 Institute of Geosciences, Friedrich Schiller University Jena, Carl-Zeiss-Promenade 10, 07745 Jena, Germany