In this paper we give a summary of technologies that are essential for phosphor developing: Characterization of the pure phosphor powders with methods like powder X-ray diffraction (XRD), optical spectroscopy, scanning electron microscopy (SEM), etc. give strong hints for and how to improve the phosphor's performance. The final proof of the phosphor's quality is obtained by application testing in the LED. Latter is a very useful tool for materials researchers and developers to adopt the phosphor to the LED device. Last but not least we demonstrate advantages of a phosphor fabrication process by using wet chemical routes in comparison to the traditional and widely applied solid state diffusion methods ("mix & fire").
Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions.
In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick.
To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.