Structure, Crystallographic Sites, and Tunable Luminescence Properties of Eu2+ and Ce3+/Li+-Activated Ca1.65Sr0.35SiO4 Phosphors

摘要

Eu2+ and Ce3+/Li+ singly doped and Eu2+/Ce3+/Li+-codoped Ca1.65Sr0.35SiO4 phosphors have been synthesized by a solidstate reaction method. The crystal structure was determined by Rietveld refinement to verify the formation of the alpha L-Ca2SiO4 phase with the Sr addition into Ca2SiO4, and the preferred crystallographic positions of the Eu2+ and Ce3+/Li+ ions in Ca1.65Sr0.35SiO4 were analyzed based on a comparison of the unit-cell volumes and the designed chemical compositions of undoped isostructural compounds Ca(2,)Sr SiO4 (x = 0.25, 0.35, 0.45, 0.55 and 0.65). Ce3+/Li+ singly activated Ca1.65Sr0.35SiO4 phosphors exhibit strong absorption in the range of 250-450 nm and a blue emission peak centered at about 465 nm. When Eu2+ ions are codoped, the emission colors of Ca1.65Sr0.35SiO4:Ce3+,Li+,Eu2+ phosphors under the irradiation of 365 nm can be finely tuned from blue to green through the energy transfer from Ce-3 to Eu-2. The involved energy-transfer process between Ce3+ and Eu2+ and the corresponding mechanism are discussed in detail. The reported Ca1.65Sr0.35SiO4:Ce3+,Li,Eu2+ phosphor might be a candidate for color-tunable blue-green components in the fabrication of near-ultraviolet-pumped white-light-emitting diodes (WLEDs).