Improvement of photoluminescence intensity of Ce-doped Y3Al5O12 phosphor by Si3N4 addition

Yttrium aluminum garnet (Y3Al5O12, YAG) has been widely used as a host for luminescent ions. The present paper describes the effects of Si3N4 addition on the formation and photoluminescence properties of the Ce-doped YAG yellow phosphors. Phosphor powders with the nominal compositions of Y2.95Ce0.05Al5-mSimO12-mNm (m = 0-0.6) were prepared by calcining the mixed raw materials at 1500 °C in nitrogen atmosphere. X-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscopy equipped with an energy dispersive x-ray spectrometer were used to characterize the structure of the calcined powders. The photoluminescence properties were measured with fluorescence spectrophotometry. It was found that in the range of m = 0-0.27, single phase YAG solid solution (s.s.) in which the Y, Al, and O sites are partially occupied by Ce, Si, and N ions, respectively. The nitrogen ions do not distribute homogeneously over the YAG lattice. The tendency to bond with nitrogen ion for the cations is (Y, Ce) > Si > Al. With the increase in the Si3N4 content, the increase in both the Ce3+/(Ce3+ + Ce4+) ratio and the CeN bonds improve the intensity of the photoluminescent emission. At m = 0.27, the emission intensity reaches a maximum which is about 2.5 and 1.6 times of that for the Si3N4-free composition (m = 0) calcined in air and nitrogen, respectively. When the Si3N4 content (m) is higher than 0.27, the emission intensity decreases due to the existence of residual Si3N4 phase.