Li_3BaSrLa_3(WO_4)8:Eu~(3+) and Its Solid Solutions : A New Red Emitting Phosphor - Structure, Synthesis and Appraisal of Optical Properties

摘要

Sequences of red emitting Eu~(3+)activated Li_3BaSrLa_3(WO_4)_8 were, synthesized by following an accustomed solid state reaction method. The concentration of the Eu~(3+) ion was varied in the Li_3BaSrLa_3(WO_4)_8 host lattice in steps of 0.3. From the concentration optimization analysis, it was observed that the (Li_3BaSrEu_2.7La_0.3(WO_4)_8) phosphor composition shows highest emission intensity. Further, we fixed the Eu~(3+) ion concentration, and efforts have been made to establish a solid solution amid the tungstate and molybdates. All the phosphor compositions exhibit broad absorption due to O ! M(M=W/Mo), O ! Eu charge transfer(CT) band and excellent photoluminescence properties, with intense electric dipole transition ( 7~ F_0 ! 5~ D_2). The detailed optical studies were indicated in order to author- ize that the Eu~(3+) ion resides at the non-centrosymmetric site residence in the interior of the host lattice. The Judd – Ofelt spectral intensity parameters were calculated. The absolute quantum yield and lifetime of the red phosphors were also measured for selected compositions. It was observed that the selected phosphors yield a high value of QY (89.8%) with enhanced absorption and emission properties. The best solid solution phosphor composition was used for LED fabrication by integrating with 395 nm near UV LED, forward biased at 20 mA. The leading optical characteristics of the phosphors may find versatile applications in the field of lighting (including SSL) as well as other essential fields.