White light-emitting Mg 0.1Sr 1.9SiO 4:Eu 2+ phosphors

Abstract

Divalent europium-activated strontium orthosilicate Sr 2SiO 4:Eu 2+ and Mg 0.1Sr 1.9SiO 4:Eu 2+ phosphors were synthesized through the solid-state reaction technique. Their luminescent properties under ultraviolet excitation were investigated. The X-ray diffraction (XRD) results show that these phosphors are of α′-Sr 2SiO 4 phase with a trace of β-Sr 2SiO 4. Doping of Eu 2+ ion into the crystal lattice results in the lattice constant being expended, while Mg 2+ makes the lattice constant shrinking. A solid solution with the same crystal structure is formed when Eu 2+ or Mg 2+ substitutes part of Sr 2+ ions and occupies the same lattice sites. The Sr 2SiO 4:Eu 2+ phosphors show two emission spectra peaked at 535 and 473 nm originated from the 5d–4f transition of Eu 2+ ion doped in two different Sr 2+ sites in the host lattice. By substitution of 0.1 mol of Sr 2+ with Mg 2+, these two emission bands are tuned to be in the blue and yellow region (459 and 564 nm for Mg 0.1Sr 1.88SiO 4:Eu 0.02), respectively. The tuning effect is discussed. With a combination of the blue and yellow emission bands the phosphors show white color, indicating that these phosphors may become promising phosphor candidates for white light-emitting diodes (LEDs).