Ba1.3Ca0.7SiO4:Eu2+,Mn2+: A Promising Single-Phase, Color-Tunable Phosphor for Near-Ultraviolet White-Light-Emitting Diodes

In this paper, Eu2+-doped and Eu2+/Mn2+-codoped Ba1.3Ca0.7SiO4 phosphors were synthesized by means of a conventional solid-state reaction process. The single-phase purity was checked by means of X-ray diffraction and the Rietveld method. Under excitation at 390 nm, the emission spectra of the Eu2+-doped phosphors exhibit a broad-band emission centered at 500 nm caused by the electric dipole allowed transition of the Eu2+ ions. The emission spectra of codoped phosphors show one more broad emission centered at 600 nm attributable to the transitions from the T-4(1)((4)G) -> (6)A(1)(S-6) of Mn2+ ions. The luminescent color of the codoped phosphors can be easily adjusted from blue to red with variation of the Mn2+ content. The energy transfer mechanism from the Eu2+ to Mn2+ ions in Ba1.3Ca0.7SiO4 phosphors has been confirmed to be the resonant type via dipole-quadrupole interaction, and the critical distance has been calculated quantitatively. All these results demonstrate that the Eu2+/Mn2+-codoped Ba1.3Ca0.7SiO4 phosphors can be a promising single-phase, color-tunable phosphor for near-UV white-light-emitting diodes after a further optimization process. Additionally, a great red shift from 593 to 620 nm has been observed following the increase of Mn2+ content, and the phenomenon has been discussed in relation to the changes in the crystal field surrounding the Mn2+ ions and the exchange interactions caused by the formation of Mn2+ pairs.