Luminescent mixed-framework silicates and zirconosilicates

• Applicant: Dr. Maria Wierzbicka-Wieczorek
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2012 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 225986172

The primary aims of the project are the synthesis, crystallographic, and spectroscopic characterization of novel microporous silicates and zirconosilicates with a mixed-framework structure containing both SiO4 tetrahedra and REE3+O6 octahedra and additional Zr4+O6 octahedra in the case of zirconosilicates. Such mixed-framework silicates and related compounds exhibit highly promising zeolitic properties (i.e., shape-selective catalysis and separation, adsorption and ion exchange for the immobilisation of toxic or radioactive cations and anions) and non-zeolitic properties such as luminescence, ion conductivity and magnetism. The mixed-framework silicates and zirconosilicates with Ln3+ cations have technologically interesting and useful properties, especially luminescence properties, which are of great interest for a wide range of photonic applications. Therefore, a comprehensive physico-chemical characterization of novel microporous mixed-framework silicates and zirconosilicates containing trivalent rare earth elements with octahedral coordination or larger coordination numbers shows considerable promise for the development of advanced materials. A further aim is to develop and improve the methodologies of flux growth of microporous silicate compounds. The syntheses of the novel microporous silicates and zirconosilicates will be carried out using flux and hydrothermal techniques, respectively. Trivalent REE3+ cations (La3+, Lu3+, Y3+, Sc3+) will be combined with SiO2 or ZrO2-SiO2 as well as with selected alkali (K+, Rb+, Cs+) and alkaline-earth metals (Sr2+, Ba2+). The crystal structures of the obtained compounds will be determined using single-crystal and powder X-ray diffraction (XRD) methods. Structural changes will be investigated by XRD as well, using a humidity and a low- and high-temperature chamber. Luminescence spectroscopy and optical absorption spectroscopy will be used to detect emission properties of Ln3+ centers in various host materials (partly doped), and especially to characterize the band sub-splitting due to crystal-field effects. Further characterizations will be made by chemical analysis (SEM, EMP) and spectroscopic analysis (IR, Raman).It is expected that new mixed-framework compounds with technologically interesting and useful properties will be discovered by the proposed strategic research. Furthermore, crystal-chemical guidelines will show how to further improve and/or tailor these properties.

• DFG Programme: Research Grants
• International Connection: Austria, France
• Participating Persons: Professor Dr. Lutz Johannes Nasdala; Professor Dr. Gerard Panczer; Professor Dr. Matthias Westerhausen