Study On Flux Reaction Of Luminophor SrAl₂O₄: Eu²⁺, Dy³⁺

As an important series of long afterglow luminescent materials, aluminate has been paid much attention recently for high emitting efficiency and good chemical stability. The luminophor SrAl₂O₄:Eu²⁺, Dy³⁺ is used as one of the most important long afterglow luminescent materials. However, H3BO3 as an important materials in Eu²⁺, Dy³⁺ co-activated strontium aluminates luminescent material, study status was rich in laboratory, but rare in industrial production. In the thesis, considering the development and practical application in aluminates long afterglow luminescent material, the flux reaction was investigated in industrial production. The body of this thesis is that luminophor SrAl₂O₄:Eu²⁺, Dy³⁺ was synthesized by solid state reaction method and co-precipitation method respectively with H₃BO₃ and (NH₄)₂HPO₄ as raw materials, aiming at the high yielding rate and extra best quality in the production. The flux reaction is discussed to offer the technical support to low the product cost, and to improve the performance-price ratio of the phosphor. The main investigation works have been done as follows:1. According the research status of the aluminate long afterglow luminescent materials with H₃BO₃ as an important flux, in this thesis, it was studied the effect of the amount of H₃BO₃, preparation condition, and molecule uniformity on the production charaxcteristic. The crystalline structure, morphology, and luminescent performance of strontium aluminates were characterized by XRD, SEM, EX, EM and decay curve respectively. The effect of the H₃BO₃ amount on the afterglow characteristic of SrAl₂O₄:Eu²⁺,Dy³⁺ was consistent in these two different ways. The appropriate amount of H3BO3 was 5mol%. This result demonstrates that synthetic method has little effect on the afterglow characteristics, which is beneficial to the double flux system. Furthermore, it is shown that the homogeneous co-precipitation method reduces the sintering temperature with about 100℃compared with that of solid state reaction method.2. The SrAl₂O₄:Eu²⁺,Dy³⁺ luminescent material was sintered by solid state reaction method. The idea of mixture of (NH₄)₂HPO₄ and H₃BO₃ as double flux was put forward based on flux character under different temperature and time according to the kinetic and thermodynamic theory in solid state reaction. The experiments embarked on the luminescence performance of the powder with different amount of flux, different sinter temperature, sintered time and other key technical conditions to obtain high quality production. The crystalline structure, morphology, and luminescent performance of strontium aluminates were characterized and analyzed by XRD, SEM, EX, EM and decay curve respectively. The optimal technology was obtained by the data of the experiments and theory. It was found that sintered body was local dense structure with air cavity, the growth of grains was significantly inhibited and grain boundary was clear from the SEM photos with 2.5 mol% (NH₄)₂HPO₄ and 5 mol% H₃BO₃, which is quite different from that of sintered body with single H₃BO₃. It indicated (NH₄)₂HPO₄ facilitating a complete response in terms of sintered body. The luminous performance was improved 10 percent through this technology that was adopted in industry production. Moreover, analysis of the thermoluminescence spectra was carried out with different flux. It showed that the thermoluminescence spectra changed with the addition of the (NH₄)₂HPO₄. The area of the spectra was increased and the shape was like trapezia. The intensity of the spectra was the tallest. The depth of trap energy was almost equal though the calculating the thermoluminescence spectra. It indicated that trap energy was same nearly with different flux in the cell structure of SrAl₂O₄ phosphor. So, emission spectra hold the line in the original structure. And the different electron-cavity compounding speed and seized electron probability in the matrix bring on the different the brightness and different time of afterglow.