Emerging blue-UV luminescence in cerium doped YAG nanocrystals

Time-resolved luminescence properties of Ce$^{3+}$ doped Y$_3$Al$_5$O$_{12}$ (YAG) nanocrystals have been studied by means of vacuum-ultraviolet excitation spectroscopy. It was discovered that additionally to the regular Ce${3+}$ yellow-green emission which is well-known luminescence in YAG, new emission covering a broad spectral range from 2.7 eV to 3.5 eV was revealed in the luminescence spectra for all YAG:Ce nanocrystals studied. This blue-UV emission has fast decay time about 7 ns as well as intensive well-resolved excitation band peaking at 5.9 eV and, in contrast to green Ce${3+}$ emission, practically is not excited at higher energies. The origin of the blue-UV emission is tentatively suggested and discussed