Nanocrystalline oxide ceramics prepared by high-energy ball milling

Studies of grain size effects in nanocrystalline materials require a preparation technique which allows adjustment of the grain size. We prepared various nanocrystalline ceramics by high-energy ball milling. The investigated systems are the oxide ceramics Li2O, LiNbO3, LiBO2, B2O3, TiO2 as monophase materials and the composite material Li2O: B2O3. The average grain size was adjusted by variation of the milling time. It was determined via line broadening of X-ray diffraction patterns (XRD) and directly with transmission electron microscopy (TEM). Thermal stability and thermally induced grain growth of the samples can be observed with differential thermal analysis and X-ray analysis. Further information concerning the structure of these heterogeneously disordered materials was extracted from nuclear magnetic resonance (NMR) and infrared spectroscopy. Li diffusion in the lithium-containing compounds is studied with ac conductivity measurements, as well as [Li-7] NMR relaxation spectroscopy. The TiO2 is interesting for research on catalytic activity. Ball milling not only causes particle size reduction, but may also lead to phase transitions and chemical reactions. This was verified with XRD.