Enhanced Red Emission in Lithium Doped CaWO4:Eu3+ and CaMoO4:Eu3+ Phosphor
The lithium ions doped red-emitting phosphors of (Ca,Eu)WO4 and (Ca,Eu)MoO4 were synthesized by solid-state reaction method, and their luminescent properties were investigated. The XRD patterns show that the phosphors are isostructural and share a tetragonal scheelite structure, even some lithium ions are doped. The excitation spectra consist of broad charge transfer bands in the short-wave UV region of W6+→O2- and Eu3+→O2- with three sharp lines around 395, 465 and 535 nm of the Eu3+ 4f excitation transitions. The characteristic emissions of WO4 2- and MoO4 2- are quenched absolutely and red light emission of Eu3+ exhibits predominate peak around 615 nm due to the electric dipole energy transition of 5D0→7F2. Excited with 395 nm, the evident enhanced emission of the phosphors were observed when Li+ doped in the host, which implies that the addition of some Li+ is beneficial for the energy transfer from WO4 2- or MoO4 2- to Eu3+.
Young Won Chang, Nack J. Kim and Chong Soo Lee
S. K. Shi et al., "Enhanced Red Emission in Lithium Doped CaWO4:Eu3+ and CaMoO4:Eu3+ Phosphor", Materials Science Forum, Vols. 561-565, pp. 1081-1084, 2007