Preparation of Blue Phosphor SrAl_2Si_2O_8∶Eu~(2+) with Sol-gel Method

Much attention has been paid to search for high-efficient phosphor with the development of displaying device. Some commercial blue phosphors, such as BaMgAl10O17: Eu(superscript 2+) do not meet the ever demanding requirements, they suffer decreasing performance of brightness and color quality because of the serious deterioration. New blue phosphor with stable hosts was belived to be a better way to solve this problem. In the silicate host series, Eu(superscript 2+) appeared to be a feasible candidate for the blue emitting vehicle originating from 5d-4f (around 420 nm) transition. SrAl2Si2O8: Eu(superscript 2+), a potential excellent blue phosphors suitable for making PDP device and other luminescent apparatus, are conventionally prepared using solid-state reaction at high temperature. However, it is difficult to control over particles size and crystal structure at this condition, meanwhile the reaction temperature is so high, serious challenging problems arise to the equipment. Sol-gel method is one of the ”soft” chemical methods, which have been employed successfully to prepare phosphor particles with better morphology and operate in a lower temperature, compared with solid-state reaction, in recent years. We reported the synthesis of the blue rare earth phosphor SrAl2Si2O8: Eu(superscript 2+) by sol-gel method. The sol-gel method was adopted by reacting corresponding nitrate and tetraethylothosilicate (TEOS) at a 85℃ water bath to form a gel, from which the dried precursor was reduced at relatively low temperature of 921℃ to generate a blue fluorescence material SrAl2Si2O8: Eu(superscript 2+). The product synthesized was characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), and fluorescence spectrophotometry. Influential factors in the process of the sol-gel preparation, such as pH value, ethanol content, amount of citric acid, were studied in depth, and the optimal conditions for synthesizing SrAl2Si2O8: Eu(superscript 2+) were determined. XRD analysis indicates that when the mole ratio between citric acid and metal ion was 1: 1, the minimal amount of anhydrous ethanol sufficient to secure a total dissolution of tetraethylothosilicate was used, and the pH value between 1.0~2.0 was maintained, the pure SrAl2Si2O8 with hexagonal crystal phase could be obtained. The light emitting analysis showed that with the monitoring wavelength 463 nm emission the product gave an exited peak at 327 nm, and an incident light with wavelength 394 nm could generate a fluorescent light with emitting wavelength 468 nm from this phosphor.