Luminescence response and CL degradation of combustion synthesized spherical SiO2:Ce nanophosphor

This study was aimed to systematically investigate the luminescence response of SiO2:Ce3+ nanophosphors with different excitation sources. The powders were synthesized by using an urea assisted combustion method. SiO2:Ce1m% samples were also annealed at 1000 °C for 1 h in a charcoal environment to reduce incidental Ce4+ to partial Ce3+ ions. High resolution transmission electron microscopy (HRTEM) images of the as synthesized and annealed powder samples confirmed that the particles were spherical and in the size range of 3–8 nm in diameter. X-ray diffraction (XRD) and electron dispersion spectroscopy (EDS) results showed that the SiO2 was crystalline and pure. Diffused reflectance, photoluminescence (PL) and cathodoluminescence (CL) results of the SiO2:Ce3+ samples were obtained and compared with each other. The CL degradation and the surface reactions on the surface of the SiO2:Ce3+ were studied with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). A clear improvement in the chemical stability of the SiO2:Ce3+ annealed at 1000 °C were obtained.

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► A simple combustion reaction and post annealing process were adopted to generate SiO2:Ce nanocrystalline phosphor.
► The annealing under reductive carbon–oxygen environment rendered a partial conversion of Ce4+ to Ce3+ ions.
► Excellent spectroscopic behavior of SiO2:Ce3+ under various excitation stimuli is evaluated and discussed.
► The long term columbic aging and luminescence output are monitored under a continuous 2 kV accelerated electron flux.
► Simultaneous presence of Ce3+ and Ce4+ states in SiO2 host has been resolved using X-ray photoelectron spectroscopy (XPS).
► The formation of a sub-stoichiometric SiOx(x < 2) layer is responsible for CL degradation.