Preparation of Eu-doped alkaline-earth silicate phosphor particles by using liquid-phase synthesis method

Abstract

The liquid-phase synthesis method for preparing Eu-doped alkaline-earth silicate phosphor particles, which is expected to be applied for lighting apparatuses, such as mercury-free fluorescent lamps and flat-plane displays, such as PDP, was investigated. The sols, as the phosphor particle precursors, were synthesized by sol–gel processes under various conditions in the liquid-phase. The particle sizes of the sols were almost uniform, and they were under 200 nm. The metal elements ratio of the sol-particles could be controlled by the initial concentration of the synthesis solutions. The sol-particles were converted from an amorphous composition into an Eu-doped alkaline-earth silicate phosphor by heat-treatment at a lower temperature compared to the conventional premixed combustion method. The crystallinity of the phosphor particles was increased with a heat-treating temperature up to 1300 °C, but an undesirable aggregation was enhanced at a higher temperature closer to its melting point (1391 °C). Therefore, these properties of reactivity and crystallinity at a lower temperature, as the precursors indicated, are very important characteristics for dispersibility because phosphor particles must be well dispersed in order to apply them to the lamp and display applications. The phosphor particles showed spectra with an emission peak of Eu 2+ at a 446 nm wavelength and the emission intensity was sensitive to the composition.