Warm white-light generation in Ca9MgNa(PO4)7:Sr2+, Mn2+, Ln (Ln=Eu2+, Yb3+, Er3+, Ho3+, and Tm3+) under near-ultraviolet and near-infrared excitation

To obtain warm white-light emission, a series of Ca9MgNa(PO4)7:Sr2+, Mn2+, Ln (Ln=Eu2+, Yb3+, Er3+, Ho3+, and Tm3+) phosphors were designed and their photoluminescence properties under near-ultraviolet and near-infrared excitation were studied. For near-ultraviolet excitation, blue-white emission is produced initially in the Eu2+ single-doped Ca9MgNa(PO4)7, whose excitation band can well match with the near ultraviolet LED chip. By introducing Sr2+ ions into Ca9MgNa(PO4)7:Eu2+, the Eu2+ emission band beyond 500 nm is enhanced obviously. Correspondingly, the emitting light color is tuned to nearly white. To generate warm white light further, Mn2+ is doped into the Ca8.055MgNa(PO4)7:0.045Eu2+, 0.9Sr2+ and the correlated color temperature is decreased largely. For near-infrared excitation, the green, red, and blue emissions have been obtained in the Yb3+-Er3+, Yb3+-Er3+, and Yb3+-Er3+ co-doped Ca9MgNa(PO4)7 phosphors, respectively. And warm white light is also produced in the Ca9MgNa(PO4)7:Yb3+, Er3+, Ho3+, Tm3+ under 980 nm excitation.