Synthesis and characterization of silicate based milarite type A2Mg3Zn2Si12O30 AND A3Mg4LiSi12O30 A Na K Eu3 activated red phosphors for pc led and forensic applications

Abstract

Recently, rare earth (RE) activated luminescent material has been newlinethe subject of extensive research due to its many advantages, including good newlineoptical properties and high stability, and has been applied in a variety of newlineapplications, such as pc-converted white light emitting diodes (WLEDs), newlineanticounterfeiting, and latent fingerprinting. Due to their fluorescence nature, newlinethe luminescent materials used in latent fingerprint visualization offer better newlinespatial resolution, high contrast, high visibility, high selectivity, and low newlinebackground noise. In addition, the luminescence anti-counterfeiting approach newlineoffers the benefits of high stability, an easy design, high luminescence intensity, newlineand effective concealment. Among various rare-earth, trivalent europium is best activator due newlineto their high quantum efficiency, high colour purity resulting from the narrow newlineband emission (FWHMlt30nm) and have been studied extensively in various newlinehosts. However, due to the high inversion symmetry at the Eu3+ substituted site newlineand the proximity of adjacent Eu3+ ions, the luminescent efficiency of the red emitting phosphors is constrained by the concentration quenching effect. In order to maximize luminous efficiency with high quenching concentration, it is essential to look into a suitable host matrix with low inversion symmetry of the doping site and considerable distance between activator neighbour sites. Based on the literature review, silicate-based milarite type host matrices have been newlinechosen for the present investigation due to their high chemical stability, newlineexcellent thermal stability, and rigid structure, which is analogous to that of newlineperovskite and spinel structures due to the presence of strong covalent Si-O newlinebonds. Additionally, it provides trivalent RE elements with low symmetry and newlineseveral doping centers. A milarite-type structure having the general formula newlineAXM3M 2Si12O30 crystalizes in a hexagonal structure having the space group newlinep6/mcc newline newline