The broad emission at 785nm in YAG:Ce³⁺,Cr³⁺ phosphor

Luminescence of defects and/or impurities is important for phosphors. One broad emission band centered at 785nm was observed in (Y_0.97Ce_0.03)₃(Al_1-xCr_x)₅O₁₂ (x=0.005, 0.01, 0.03, 0.06, 0.09), (YAG:Ce,Cr) nano-particles synthesized by polymer-assisted sol-gel method in this work. In order to study the source of this wide emission band, the crystalline phase structure of the phosphors was examined by X-ray diffraction (XRD). No obvious diffraction peaks due to impurity phase were observed even though the calcining temperature of the samples arrived at 1400°C. The anti-site defects were excluded. No detectable signals of impurities were obtained by X-ray Photoelectron Spectroscopy (XPS) or inductively coupled plasma mass spectrometry (ICP-MS). Based on the photo-luminescence results of YAG:Ce,Cr, YAG:Ce and YAG:Fe phosphors, the wide emission band is attributed to the ⁴T₁(⁴G)→⁶A₁(⁶S) transition from the trace impurity of Fe³⁺. The excitation band at 280nm is assigned to Fe³⁺-O^2- charge transfer band.