Structural and optical properties of YAG:Ce 3+ phosphors by sol–gel combustion method

Abstract

High-quality Ce 3+-doped Y 3Al 5O 12 (YAG:Ce 3+) phosphors were synthesized by a facile sol–gel combustion method. In this sol–gel combustion process, citric acid acts as a fuel for combustion, traps the constituent cations and reduces the diffusion length of the precursors. The XRD and FT-IR results show that YAG phase can form through sintering at 900 °C for 2 h. This temperature is much lower than that required to synthesize YAG phase via the solid-state reaction method. There were no intermediate phases such as YAlO 3 (YAP) and Y 4Al 2O 9 (YAM) observed in the sintering process. The average grain size of the phosphors sintered at 900–1100 °C is about 40 nm. With the increasing of sintering temperature, the emission intensity increases due to the improved crystalline and homogeneous distribution of Ce 3+ ions. A blue shift has been observed in the Ce 3+ emission spectrum of YAG:Ce 3+ phosphors with increasing sintering temperatures from 900 to 1200 °C. It can be explained that the decrease of lattice constant affects the crystal field around Ce 3+ ions. The emission intensity of 0.06Ce-doped YAG phosphors is much higher than that of the 0.04Ce and 0.02Ce ones. The red-shift at higher Ce 3+ concentrations may be Ce–Ce interactions or variations in the unit cell parameters between YAG:Ce 3+ and YAG. It can be concluded that the sol–gel combustion synthesis method provides a good distribution of Ce 3+ activators at the molecular level in YAG matrix.