Synthesis and photoluminescence properties of yellow-emitting Ca5(Zn1-xMgx)4(VO4)6 self-activated phosphors

Novel yellow-emitting Ca5(Zn1-xMgx)4(VO4)6 self-activated phosphors were synthesized via a sol-gel method. The X-ray diffraction showed their typical cubic garnet structure. The photoluminescence excitation spectra of Ca5(Zn1-xMgx)4(VO4)6 phosphors exhibited a broadband ranging from 250 to 430 nm, which was originated from the [VO4]3− group charge transfer transition. For the emission spectra, Ca5Zn4(VO4)6 and Ca5Mg4(VO4) phosphors exhibited the characteristic broadband emissions between 420 and 750 nm with highest intensities at 538 and 533 nm, respectively. The calculated CIE coordinates were (0.331, 0.476) and (0.318, 0.463) for Ca5Zn4(VO4)6 and Ca5Mg4(VO4)6 yellow phosphors, respectively. The results hint that these luminescent powders may be good candidates for their potential use in the fabrication of rare-earth elements free WLEDs.