Preparation And Properties Of Four Typical Silicate/Germinate Luminescent Materials For Light-emitting Diodes

Light-emitting diodes (LEDs) have replaced traditional light sources for display, decoration, and illumination applications due to their superior features, such as greatenergy saving, longer lifetime, and environmental friendliness. Silicates/germinates are of significant interest for use in phosphor converted white LEDs due to their high luminescence efficiency and excellent chemistry stability.A part of our work, the crystal structure of CSSF:Eu2+is determined by the Maud refinement analysis, which belongs to space group P63/m with the lattice constants a=b=9.4540A, c=6.9455A. We have investigated the luminescence properties of new blue/greenemitting CSSF:xEu2+phosphors in detail, the results show their emission spectra consist of two broad bands centered at420and525nm. The Eu2+ions simultaneously occupy two kinds of sites under350nm UV excitation:the first emission band centered at420nm could be attributed to the5d-4f emission of Eu2+ions occupying the Ca(Ⅰ) sites with4f site and nine coordination; the second band centered at525nm could be due to the5d-4f emission of Eu2+ions occupying the Ca(II) sites with6h site and seven coordination.In addition, a new Ca2La8(GeO4)6O2(CLGO) compound has been synthesized via solid-statereaction process for the first time. The crystal structure of CLGO was refined, and the photoluminescence espectra(PL), cathodoluminescence spectra(CL), and lifetimes as well as temperature dependence of photoluminescence of CLGO:RE3+(RE3+=Eu3+, Tb3+, Dy3+, Sm3+, Tm3+) were investigated. All the samples have higher than the commercial YAG:Ce3+except for CLGO:Eu3+, which demonstrate superior thermal stability as RGB luminescent materials.Another of our work, aiming to currently available commercial green and orange emitting phosphors on the market, Ca8Mg(SiO4)4Cl2:Eu2+and Sr3SiO5:Eu2+, respectively. Both of them have poor thermal stabilities. By hybridizing anionic groups and substituting cation, there was changed coordination polyhedral size and symmetry in our paper. Si element is replaced by Ge in Ca8Mg(Ge04)4Cl2host, and Sr ionic site is displaced by Ba and Mg elements. So it decreases the crystal lattice distortions after introducing the activited Eu2+ion and weakens the surrounding lattice resilience. With rising ambient temperature, stability of Eu2+ion in lattice is increasing resulted in improving thermal stabilities of phosphors.