The work is devided into two different parts. The first part deals with a new synthesis of well known phosphors. Here, we want to study a novel concept of synthesis: Microwave-assisted crystallisation of nanoscale phosphors containing adequate dopants in Ionic Liquids. Microwave heating leads to rapid heating of the reaction media. This measure results in very high reaction rates as well as in a rapid nucleation and crystallisation.

Ionic Liquids (ILs) have attracted increased attention in the synthesis of inorganic nanomaterials because of their wide liquid range, extraordinary electrochemical stability, non-volatility, tuneable solvent properties and excellent thermal stability. Due to their polarity intense absorption of microwaves and almost immediate heating under microwave irradiation occurs.

Aim of this novel concept is to combine the advantages of both, ILs and microwave heating, to realise nanocrystalline phosphors with a high crystallinity and a high quantum efficiency.

The second part deals with the study of two-photon processes in doped oxonitride phosphors and is expected to lead to the synthesis of new conversion phosphors. For studying two-photon processes, one has to achieve fine-tuning of bandgaps in an adequate crystal structure. In addition a steep absorption edge in the visible spectrum is necessary to achieve selective absorption of light.

Oxonitrides are known as thermal stable and brilliant pigments with a steep absorption edge. Through variation of cations and crystal structure the colour can be tuned from yellow to deep red.

So this system should be a promising candidate for studying two-photon processes. UV/Vis- and fluorescence-spectroscopy as well as X-ray-diffraction serve for identification and characterization of the phosphors. The particle size is measured by dynamic light scattering (DLS) and scanning electron microscopy (SEM).