Search

(Y1-xGdx)BO3:Eu (0≤x≤1) phosphor particles were prepared by spray pyrolysis. The optimal amount of boric acid for the high photoluminescence intensity of there particles differed depending on the molar ratio of Y to Gd. With decreasing Y/Gd molar ratio, an increasing amount of excess boric acid was required. The difference in excess quantity of boric acid, which was demanded for the highest photoluminescence intensity according to the Y/Gd ratio, influenced the morphology and mean size of the (Y,Gd)BO3:Eu phosphor particles. The (Y1-xGdx)BO3:Eu (0≤x≤1) phosphor particles had a regular morphology. The mean sizes of the GdBO3:Eu and YBO3:Eu phosphor particles were 1.4 and 1 µm, respectively. The high reactivity of boron and yttrium components produced YBO3:Eu phosphor particles with high photoluminescence intensities by spray pyrolysis using a spray solution with a stoichiometric amount of boric acid.

Gd2O3:Eu phosphor particles with cubic and monoclinic phases were directly prepared by high-temperature spray pyrolysis from aqueous, polymeric precursor and colloidal solutions. The colloidal solution with nanosized silica was effective for the preparation of Gd2O3:Eu phosphor particles with a cubic phase, a high photoluminescence intensity and a good morphology. The phosphor particles prepared from colloidal solutions with nanosized silica obtained by hydrolysis had a small size, a narrow size distribution, a spherical shape and a filled morphology. The optimum doping concentration of nanosized silica particles was 0.5 wt % of the product particles. The phosphor particles prepared by spray pyrolysis from colloidal solutions at temperatures below 1580 °C had the photoluminescence spectrra of the cubic phase and a maximum photoluminescence intensity at a temperature of 1560 °C.

High-brightness (CeTb)MgAl11O19 (CTMA) phosphor particles were directly prepared by high temperature spray pyrolysis. The boric acid flux added into spray solution affected the morphology and photoluminescence intensity of the CTMA phosphor. The phosphor particles prepared from spray solution with 20 wt % boric acid of the product had a spherical shape and a filled morphology at 1600°C. The phosphor particles prepared by spray pyrolysis from spray solution without flux material under reducing atmosphere at 1600°C had high photoluminescence intensities under ultraviolet. The boric acid flux improved the photoluminescence intensities of the CTMA phosphor. The maximum photoluminescence intensity of the phosphor particles prepared from spray solution with an optimum amount of added boric acid flux was 114% of that of the phosphor particles prepared from spray solution without flux material. The particles directly prepared by spray pyrolysis from spray solution with 20 wt % boric acid of the product had a pure crystal structure of the CTMA phosphor.

Nano-sized carbon black was applied in the spray pyrolysis as the nucleation seeds. Green-emitting Gd0.81Tb0.19PO4 phosphor powders were prepared by spray pyrolysis from the colloidal spray solution with nano-sized carbon black. The Gd0.81Tb0.19PO4 phosphor powders prepared from the colloidal spray solution had regular morphology and filled structure. The mean size and geometric standard deviation of the phosphor powders prepared from the colloidal spray solution were 0.95 µm and 1.5. The Gd0.81Tb0.19PO4 phosphor powders prepared from the colloidal spray solutions had similar photoluminescence intensities to that of the phosphor powders prepared from the aqueous spray solution under vacuum ultraviolet. Carbon black did not act as impurity of the Gd0.81Tb0.19PO4 phosphor powders.

Y2O3:Eu phosphor particles with a spherical shape, a fine size, and high brightness under vacuum ultraviolet (VUV) illumination were prepared by spray pyrolysis. The polymeric precursors were needed to modify the spray solution to prepare spherical particles. The use of only flux with the polymeric precursors did not produce dense and spherical Y2O3:Eu particles; that is, the produced particles were very porous. The addition of both a drying control chemical additive (DCCA) and boric acid to a spray solution containing polymeric precursors was found to produce Y2O3:Eu phosphor particles with a dense structure while maintaining the spherical morphology. According to X-ray diffraction (XRD) analysis, the DCCA induced an enhancement of crystallinity. The use of boric acid flux improved the photoluminescence (PL) intensity under VUV illumination. In addition, the use of both boric acid flux and a DCCA with polymeric precursors further improved the PL intensity owing to the enhancement of the morphology and the crystallinity.

(CeTb)MgAl11O19 (CTMA) phosphor particles were prepared by spray pyrolysis from polymeric precursor solutions under severe preparation conditions. Citric acid and ethylene glycol used as polymeric precursors formed as-prepared and post-treated (CeTb)MgAl11O19 phosphor particles with a spherical shape and a dense morphology. The CTMA phosphor particles prepared from polymeric precursor solutions at 1600°C had a completely spherical shape, a dense morphology, and a nonaggregated morphology after post-treatment at 1400°C. The CTMA phosphor particles prepared from the polymeric precursor solution had a lower impurity content than those prepared from a pure aqueous solution. All the phosphor particles prepared from the polymeric precursor solution had higher photoluminescence intensities than those prepared from the pure aqueous solution at all temperatures. The photoluminescence intensity of the CTMA phosphor particles prepared from the polymeric precursor solution was 108% that of the phosphor particles prepared from the pure aqueous solution at 1600°C.