Site-selective occupation, optical spectrum regulation and photoluminescence property investigation of Eu-activated blue light-excited yellow-orange emitting phosphors.

We report yellow-orange emitting phosphors SrCaMg(PO):0.05Eu (SCMPO:Eu, = 0.5-2.5) and SrBaMg(PO):0.05Eu (SBMPO:Eu, = 0.5-3.0) with broad emission bands (450-800 nm). All these phosphors can be excited efficiently by blue light and n-UV light. Their crystal structure, photoluminescence spectra, fluorescence decay curves and thermal stability were investigated in detail. As doping concentrations of Ca or Ba increase, Eu emitting centers will selectively occupy different Sr sites, thus leading to the regulation of optical spectra of SCMPO:Eu and SBMPO:Eu. Accordingly, the emission colors of SCMPO:Eu and SBMPO:Eu samples can gradually turn from yellow to orange when excited using 460 nm blue light. And the emission colors of a given sample can also be varied under different excitations because there are three kinds of emitting centers in SCMPO:Eu and SBMPO:Eu. In addition, introducing Ca and Ba can enhance the thermal stability of the phosphors obviously, and overall, the thermal stability of SBMPO:Eu is better than that of SCMPO:Eu. We chose SBMPO:Eu as an example to further investigate its photoluminescence properties, and found that the optimal doping concentration of Eu is 0.08, and dipole-quadrupole interaction is dominated in the concentration quenching mechanism. Furthermore, high-quality warm white light can be obtained by two ways: (a) 470 nm blue LED chip + SCMPO:Eu [CCT = 3639 K, = 82.21] and (b) 470 nm blue LED chip + SBMPO:Eu and YAG:Ce [CCT = 4284 K, = 86.69]. The excellent performances indicate that SCMPO:Eu and SBMPO:Eu are attractive candidates for warm WLEDs.