Optical properties of green-blue-emitting Ca-α-Sialon:Ce3+,Li+ phosphors for white light-emitting diodes (LEDs)

Ce3+,Li+-codoped Ca-α-Sialon phosphors with the formula [Ca(1−2x)CexLix]m/2Si12−(m+n)Alm+nOnN16−n (0≤x≤0.25, 0.5≤m≤3.5, and 0.16≤n≤2.0) have been synthesized by gas pressure sintering (GPS). The effects of the activator concentration and the overall composition of host lattice on the phase evolution, morphology, and optical properties were investigated. The single-phase Ca-α-Sialon:Ce3+,Li+ can be synthesized at x<0.1, 1.0≤m≤2.5, and n≤1.2. The synthesized powders exhibit a relatively dispersive and uniform morphology. Under the near UV excitation, the bright green-blue emission centered at 500–518 nm is observed. The photoluminescence can be tailored by controlling Ce3+ concentration and the overall composition of the α-Sialon host lattice. With increasing the Ce concentration and m value both excitation and emission bands show a red shift, which perfectly matches with the near-UV LEDs in the range of 360–410 nm. The strongest luminescence is achieved at x=0.08–0.1, m=2.0–2.5, and n=1.0. Simultaneously, the highest quantum efficiency and better thermal stability are also present.