A potential red-emitting phosphor CaSrAl2SiO7:Eu3+ for near-ultraviolet light-emitting diodes

A novel red-emitting phosphor CaSrAl2SiO7:Eu3+ was firstly synthesized through the high temperature solid state reaction at 1300 °C. The structure, diffuse reflection spectra, photoluminescence spectra, color-coordinate parameters and quantum efficiencies (QE) of phosphors were investigated. The obtained CaSrAl2SiO7:Eu3+ phosphors have the same structure with that of the Ca2Al2SiO7 and Sr2Al2SiO7 phosphor, which have the melilite structure. Optical properties were studied as a function of Eu3+ concentration x, when x>0.14, the intensity of absorption of the f-f transitions of Eu3+ at 393 nm is stronger than that of the broad charge transfer transition band (CTB) around 254 nm, and which matches well with the output lights of NUV-LEDs, whereas, the concentration of Eu3+x≤0.14, the absorption of 393 nm is weaker than that of CTB. The underlying reason of Eu3+ concentration on their luminescent properties was investigated and discussed in detail. As a result, comparing with the commercial red phosphor Y2O2S:Eu3+, the CaSrAl2SiO7:xEu3+ (x>0.14) phosphor exhibited excellent color purity and much higher brightness and could be considered as promising red phosphors for NUV-LEDs.