Lanthanide Materials for Xenon Lighting

Mercury is a ubiquitous air pollutant and one source is from the disposal of mercury lamps. It is now being replaced by xenon lighting, which is more environmentally friendly. However, since the phosphors for use in mercury lighting are almost 100% efficient and the mercury discharge is more efficient than that of xenon, the phosphors for use in xenon lighting need to be more than 100% efficient. There are two aspects to be considered. First, the xenon discharge must be efficiently absorbed by the phosphor. It is well known that the intraconfigurational transitions of lanthanide ions have weak absorption coefficients. Second, once absorbed, the vacuum ultraviolet photon must be converted into white light. Some cascade schemes involving quantum cutting have been suggested for this process by employing two co-doped ions in the host. Thus this project focuses on the optimization of the first process. Whereas wide bandgap hosts such as fluorides and oxides have previously been employed as host lattices, the project employs low-phonon chloride materials and attempt to chemically match the xenon excitation energy to the host bandgap. Then the absorption is maximized and energy transfer can occur to the co-doped ions in the host. By this arrangement, efficient absorption of the discharge and subsequent emission of white light can be realized.