163 162 Principal Scientist Profiles Lothar Wondraczek Lothar Wondraczek Principal Scientist Profiles PROFESSOR OF GLASS CHEMISTRY, OTTO-SCHOTT-INSTITUTE Professor Wondraczek is Chair of Glass Chemistry II at the Otto Schott Institute of Materials and Research (OSIM) and coordinates the priority program 1594 of the German Research Foundation (DFG). He is Chair of the committees Glass Transition of the International Commission on Glass (ICG) and Glasses and Optical Materials of the Germany Society of Materials Research, and is also council member of the German Society of Glass Science and Technology. LOTHAR WONDRACZEK RESEARCH AREAS Prof. Wondraczek‘s research activities span all areas of experimental glass science with particular focus on the exploration and development of new glass and glass ceramic compositions and surface modification techniques. His main thrusts are the optical and mechanical properties of multi-component oxide, oxynitride and oxyhalide materials. He is exploring structure-property relations with the ultimate objective of providing topology-based tools for the description of noncrystalline solids. Research interests include: • Glasses for applications in optics and energy technologies • Photoluminescence, magneto-optical materials, and fiber optics • Relaxation processes in complex systems TEACHING FIELDS Prof. Wondraczek teaches interdisciplinary materials science where he connects materials engineering, physics and chemistry. He gives courses in: • Solid state kinetics and thermodynamics • Composite and nanocomposite materials • Glasses and optical materials RESEARCH METHODS The laboratories led by Prof. Wondraczek offer state-of-the-art equipment for the fabrication and experimental characterization of glasses and other optical materials, including: • Extensive glass melting capabilities • High resolution static and dynamic luminescence spectroscopy, Raman and FTIR spectroscopy • Advanced high-temperature processing (< 2200 °C), including nitridation and hydration • Extensive thermoanalytics, including STA-MS, DSC, DTA, TGA, HP-TGA, DDSC • Extensive nanomechanical testing, including indentation, nano-scratching, nano-bending, lateral nanotesting and tribological analyses RECENT RESEARCH RESULTS The primary mission of Prof. Wondraczek‘s team is to explore topology-based tools for the design of new inorganic glasses, glass ceramics and surface modification techniques. Thereby, the term topological engineering refers to a bottom-up approach of acquiring and applying knowledge of the short- and mid-range structural architecture to derive tools for materials design. Such tools are, e.g., potentials and spatial relations between constituents at the atomistic level [1, 2], the generic design of specific short- and mid-range topology, packing density, molecular interactions occurring at surfaces and their consequences on meso- and macro-scale processes. These tools are aimed at targeting material applications in the fields of optics and photonics, as well as in energy technologies, architecture and for the automotive industry. Specifically, we are exploring and developing strategies with the goal of attaining glassy materials with superior mechanical resistance [1], optical fiber glasses and magneto-optical glasses [2, 4] and glasses for light conversion purposes [5]. At present, optical amplification for broadband telecommunication and new fiber lasers, solar spectral conversion for improved harvesting of sunlight and inorganic materials for transient optical storage via spectral hole burning techniques represent the thrusts of the group‘s activities in optics. ULTRABROAD LUMINESCENCE FROM NI2+-DOPED GLASS CERAMICS Nanocrystalline Ba-Al titanate precipitates from supercooled TiO2-BaO-SiO2-Al2O3 melts via catalyzed volume nucleation in the presence of Ni2+, forming a BaAl 2Ti6O16 hollandite-type lattice. Ni 2+-species are incorporated into the crystalline environment in octahedral co-ordination. Hollandite formation is accompanied by precipitation of tetrahedrally distorted BaTiO3 as a secondary crystal phase, where crystal species and habitus can be clearly distinguished by dark-field transmission electron microscopy. The resulting photoluminescence due to spin-allowed relaxation of 3T 2g( 3F) to 3A2g( 3F) in VINi2+ occurs from three distinct emission centers. Photoemission spans the spectral range of 1.0 to 1.6 μm. Besides red and IR laser excitation, NIR photoemission can be excited with conventional near UV light sources, i.e. in the spectral range of 350-420 nm. Decay kinetics as well as the position and shape of the emission band can be adjusted by dopant concentration and synthesis conditions [5]. [1] Wondraczek et al., Adv. Mater. 23, 4578 (2011). [2] Schmidt et al., Adv. Mater. 23, 2681 (2011). [3] F. Angeli et al., Phys. Rev. B 85, 054110 (2012). [4] Winterstein et al., Opt. Mater. Express 3, 184 (2013). [5] Gao et al., J. Mater. Chem. 22, 25828 (2012). Contact: Phone: + 49 3641 9-48500 Email: lothar.wondraczek@uni-jena.de
RkJQdWJsaXNoZXIy OTI3Njg=