Optical and structural characterization of nanostructured Y2O3:Tb

Nanophosphors correspond to nanostructured, inorganic, insulating solid materials that emit light under particle or electromagnetic excitation. Although extensive investigation of the optical properties of nanostructured semiconductors is underway, nanophosphors remain largely unexplored. Nanophosphor Tb-doped Y2O3 was obtained by the solution combustion technique with Tb concentrations up to 5 at.%. Structural characterization, assessed by transmission electron microscopy and x-ray diffraction, show the existence of nanoparticles with a cubic crystallographic structure and sizes in the 30 to 70 nm range. As a result of the combustion process, the nanoparticles agglomerate into large micron-sized entities. Photoluminescence emission and excitation spectra obtained at room temperature show distinct differences in the optical behavior of the bulk and nanomaterial. Specifically, the excitation spectra of the nanophosphors are systematically blue-shifted relative to bulk spectra. The photoluminescence emission spectra, which originates from D-5(4) -> F-7(J) transitions comprising several sharp lines in the visible spectrum, also exhibit contrasting behavior upon Tb incorporation; the D-5(4) -> F-7(5,6) intensity ratio decreases with increasing Tb content in the bulk but is constant in the nanophosphor. Finally, the maximum in the quenching curve of the nanostructured material occurs at 1.5 at %, which is three times higher than for the bulk material.