Synthesis and characterization of nanophosphors by flame spray pyrolysis

Three different types of nanophosphor materials were prepared by flame spray pyrolysis (FSP) from nitrate-based liquid precursor. Rare-earth doped binary oxide nanophosphor particles were obtained from urea-added liquid precursor using FSP without post-heat treatment. Also, rare-earth doped ternary oxide nanophosphors were prepared from urea-added using FSP with less annealing temperature and reduced time. In addition, metal-ion doped ternary oxide nanophosphors could be easily generatred by FSP from nitrate-based liquid precursor. The prepared phosphor particles properties such as crystallinity, luminescence properties, surface morphology and particle size were investigated by many techniques in order to obtain the optimum condition for high quality nanophosphor particles.;Firstly, Y2O3:Eu3+ nanophosphor was synthesized by FSP from nitrate-based liquid precursor. Urea was added to the liquid precursor to enhance the crystallinity of Y2O 3:Eu3+ phosphor particles. The resultant phosphor particles showed Y2O3:Eu3+ cubic phase in the XRD pattern without the need for post-heat treatment. The influence of synthesis conditions such as different molar concentrations of urea, overall molar concentration of liquid precursors, and doping concentration on luminescent properties was investigated. The particle size of product was found to be in the range of 20--30 nm as determined from transmission electron microscopy (TEM) images. Photoluminescence (PL) measurement of the synthesized Y2O 3:Eu3+ nanophosphor show peak in red region of visible spectrum with a maximum peak at wavelength of 609 nm when excited with 398 nm wavelength photons.;Secondly, YAG:Ce3+ nanophosphors were synthesized by FSP from nitrate-liquid precursor. As-prepared nanoparticles were annealed in the temperature range of 800°C to 1100°C for 1 hour. The influence of addition of urea and the molar ratio of yttrium to aluminum in the liquid precursor on crystallinity and luminescence properties of YAG:Ce3+ nanophosphor particles were studied. The heat-treated phosphor particles were spherical in shape with an average size blow 50 nm. The crystallinity of YAG:Ce3+ nanophosphors improved with addition of urea and overloaded aluminum in starting liquid precursor. In addition, high PL intensity with pure YAG:Ce3+ phase was observed for phosphor particles prepared with addition of urea and excess of aluminum in liquid precursor with less annealing temperature and reduced time compared to other methods.;Green emitting Zn2SiO4:Mn2+ phosphor particles were synthesized by FSP from a function of different liquid precursors. Luminescence and crystalline properties were investigated as the different Zn-source materials in aqueous precursor. Also, the influence of post-heat treatment temperatures on the crystal structure and PL intensity of Zn 2SiO4:Mn2+ nanophosphors was investigated. Mn-doped zinc silicate crystalline structures were obtained when annealed at 1000°C for 1 hour. The emission peak was found at 525 nm. Furthermore, the effect of the flame temperatures by varying methane flow rate on the crystallinity and luminescence properties of Zn2SiO4:Mn2+ nanophosphors was investigated. The phosphor particles prepared from high flame temperature showed good crystallinity with pure zinc silicate phase and the maximum PL intensity. We conclude that different experimental conditions such as liquid precursor prepared from different Zn-source and annealing temperature influence both crystallinity and the luminescence properties of Zn2SiO 4:Mn2+ nanophosphors.