Abstract: A series of NSPO∶0.06Tm³⁺, yDy³⁺(y=0~0.10) phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology and luminescent properties of the phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrometer. Under the excitation of 360 nm, the photoluminescence (PL) spectrum of Na₃Sc₂(PO₄)₃∶Tm³⁺,Dy³⁺ shows the Tm³⁺ characteristic emission peak at 457 nm and three characteristic emission peaks of Dy³⁺ at 483, 577, and 672 nm, respectively. There is an energy transfer from Tm³⁺ to Dy³⁺ ion in Na₃Sc₂(PO₄)₃∶Tm³⁺,Dy³⁺ phosphor due to the good overlap between the emission spectrum of Na₃Sc₂(PO₄)₃∶Tm³⁺ and the excitation spectrum of Na₃Sc₂(PO₄)₃∶Dy³⁺, which is further confirmed by the fluorescence lifetime decrease of Tm³⁺ ion with the increase of Dy³⁺ concentration. The process of energy transfer is via dipole-dipole interaction which is confirmed by applying Dexter and Reisfeld's theory. By increasing the Dy³⁺ concentration, the color coordinates of the Na₃Sc₂(PO₄)₃∶0.06Tm³⁺,yDy³⁺ phosphors could be adjusted from blue to white, and then to yellow. The Na₃Sc₂(PO₄)₃∶0.06Tm³⁺,0.06Dy³⁺ phosphor shows fairly good resistance to thermal quenching with a high preservation of the emission intensities of 97.6%, 89.2% and 78.6% at 423, 473 and 523 K, respectively. These results suggest that the Na₃Sc₂(PO₄)₃∶Tm³⁺,Dy³⁺ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white light-emitting diodes (LEDs).

Key words: White phosphor, Thermal quenching, Light-emitting diodes