Luminescence of Y3AL5O12 nano-particles doped with praseodymium ions

We have investigated the spectroscopic properties of the praseodymium ion in a Y3Al5O12 (YAG) nano-powder with an average particle size of 58 nm as function of temperature between 29 K and 300 K. The luminescence spectra were obtained by exciting selectively the sample at 460 and 609 nm, resulting in the excitation of the 3P0 and 1D2 levels, respectively. With excitation in the 3P0 level, emissions from this level and from the 1D2 level were observed. Time resolved spectra and decay pattern inspection were used to assign spectral lines to specific radiative transitions. With excitation of the 1D2 level, luminescence emitted by the same level and up-converted emission from the 3P0 level were observed.We have compared the spectral characteristics of the nano-particles with those of a YAG crystal doped with the same ion. We have uncovered differences in the dependence of the lifetime on temperature, widths of the spectral lines, shapes of the decay patterns following pulsed excitation, and mechanism of up-conversion. We present a model that emerges from our measurements and that explains the difference in the behavior of the crystal and of the nano-particles.

Time resolved luminescence spectra of the nano-powder YAG:Pr3+ (a) and bulk YAG:Pr3+16 (b) with the time delays 2, 8, 20, and 100 μs in the 605 and 630 nm wavelength range at 29 K. (The excitation was into the 3P0 level with the dye laser tuned at 460 nm.)Figure optionsDownload high-quality image (85 K)Download as PowerPoint slideHighlights
► Size of YAG nanopowder strongly affects the dynamics of the Pr luminescence.
► Life time data show the existence of different sites for the Pr in YAG nanopowder.
► Multiphonon relaxation at high temperatures is very strong for the nanoparticles.
► Life time of Pr in nanopowder is shorter at each temperature than YAG:Prcrystals.
► Nano-size affects the width of the luminescence lines of Pr.