The correlation between the crystal structure and luminescent properties of Eu3-doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A4-3x(WO4)2:Eux 3 (A=Li, Na, K) and B(4-3x)/2(WO4) 2:Eux3 (B=Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f4f electron transition of Eu3 ions. The high doping concentration of Eu3 enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu3-doped metal tungstate phosphor, the critical energy transfer distance is larger than 5 Å so that exchange interactions between Eu3 ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu3 ions, which causes a decrease in red emission with increasing concentration of Eu3, appears to be due to electric multi-polar interactions. In addition, the EuO distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5D0→ 7F2 transition of Eu3.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics