Broadband UV-to-green photoconversion in V-doped lithium zinc silicate glasses and glass ceramics.

We report on photoluminescence of vanadium-doped lithium zinc silicate glasses and corresponding nanocrystalline Li2ZnSiO4 glass ceramics as broadband UV-to-VIS photoconverters. Depending on dopant concentration and synthesis conditions, VIS photoemission from [VO4]3 is centered at 550-590 nm and occurs over a bandwidth (FWHM) of ~250 nm. The corresponding excitation band covers the complete UV-B to UV-A spectral region. In as-melted glasses, the emission lifetime is about 34 μs up to a nominal dopant concentration of 0.5 mol%. In the glass ceramic, it increases to about 45 μs. For higher dopant concentration, a sharp drop in emission lifetime was observed, what is interpreted as a result of concentration quenching. Self-quenching is further promoted by energy transfer to V4+ centers (2<Гt4→2Гt3). Partitioning of vanadium into V5+ and V4+ was examined by electron paramagnetic resonance and X-ray photoelectron spectroscopy. Suppression of V5+-reduction requires careful adjustment of the optical basicity of the host glass and/or synthesis conditions.