Evolution of Luminescence of Sr2-y-zCazSi(O1-xNx)4:yEu2+ with N3-, Eu2+, and Ca2+ Substitutions

Sr2-y-zCazSi(O1-xNx)(4):yEu(2+) (SCSON:Eu2+) solid solutions were prepared by substituting N3-, Eu2+, and Ca2+ ions into Sr2SiO4 (SSO). These ions contributed differently to the evolution of luminescence of SCSON:Eu2+. SSON:Eu2+ (z = 0) has two activation centers: Eu(I) and Eu(II). The nitridation effects led to a dramatic change in the crystal field surrounding the Eu(1) site but rarely affected the Eu(I) site. Accordingly, SSON:Eu2+ exhibited broad excitation spectra from ultraviolet to visible wavelengths. In comparison with the Eu(II) green emissions of SSO:Eu2+, the dominant peak wavelengths (DPWs) of the Eu(II) emissions were at red emission regions (605-630 nm), depending on the amount of Eu2+ ions. The Ca2+ ions of SCSON:Eu2+ preferentially changed the emission wavelength assigned to Eu(I) and affected the Eu(II) emission intensity. In addition to the spectral properties, the chromaticity coordinates and a low thermal quenching behavior of SCSON:Eu2+ powders demonstrated that they can be a novel red phosphors for use in white light emitting diodes.