Luminescence and excitation energy transfer in rare earth-doped Y4Al2O9 nanocrystals

The nanocrystalline powders of Y4Al2O9 single doped with Nd3+, Yb3+, Er3+ and co-doped with Nd3+ and Yb3+ as well as with Yb3+ and Er3+ were obtained by a modified sol-gel method starting from nitrates and acetates rather than citrates. The powders were characterised by X-ray diffraction method, high resolution scanning electron microscopy and luminescence spectroscopy. Close similarity of low temperature emission spectra recorded for Y4Al2O9 nanocrystalline powder doped with Nd3+ and for a single crystal counterpart grown by the micro-pulling technique implies that the sol-gel method applied is able to provide material in which the structural peculiarities encountered in bulk crystals are maintained. Efficiency of nonradiative energy transfer between rare earth ions was assessed based on analysis of luminescence decay curves. It has been concluded that the Y4Al2O9 host may be promising for the design of multiple doped phosphors whose emission characteristics are tailored by energy transfer between properly chosen activators.