Synthesis of Cerium-Activated Yttrium Aluminate Based Fine Phosphors by an Aerosol Route Articles uri icon

publication date

  • June 2012

start page

  • 2716

end page

  • 2724

issue

  • 16

volume

  • 2012

International Standard Serial Number (ISSN)

  • 1434-1948

Electronic International Standard Serial Number (EISSN)

  • 1099-0682

abstract

  • Polycrystalline fine powders of yttrium aluminate doped with Ce3+ were synthesised by spray pyrolysis of a polymeric precursor, which was obtained by dissolving the corresponding nitrates in a solution of ethylenediaminetetraacetic acid (EDTA) in ethylene glycol (EG). Aerosol decomposition was performed at 550 °C followed by an additional thermal treatment (900&-1100 °C). The yield of either a single yttrium aluminium perovskite (YAP) phase or a single yttrium aluminium garnet (YAG) phase was investigated as a function of the predefined yttrium/aluminium ratio, the cerium doping concentration, the processing temperature, and the thermal-treatment regime, which included the variation of the heating and cooling rates (dT/dt), the residence time (tau), and the atmosphere. Changes in the composition and structure of the precursor during thermal decomposition were investigated by thermogravimetric and differential thermal analysis (TGA/DTA) and FTIR spectroscopy. The particle morphology and structure were analysed by a combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) and by high-resolution transmission electron microscopy (HR-TEM). The structural refinement was based on the phase identification performed by X-ray powder diffraction (XRPD). The emission spectra were recorded within the range 325&-800 nm by applying excitation wavelengths of 297 (YAP) and 450 nm (YAG). The employed synthesis conditions assured the formation of spherical, non-agglomerated particles with well-developed surfaces and diameters between 200 and 800 nm. For a predefined Y/Al ratio of 1:1, lower processing temperatures combined with longer heat treatments under stationary conditions resulted in a multiphase system, composed of YAP, YAG, and monoclinic yttrium aluminate (YAM) phases. However, a short heat treatment with a high heating rate (200 °C/min) at higher temperatures results in the formation of a kinetically favoured pure YAP hexagonal phase.

keywords

  • yttrium aluminates; nano-particles; luminescence; polymerization; spray pyrolysis