Eu~(3+) co-doped Sr_3Gd(PO_4)_3:Dy~(3+) phosphors: luminescence properties and color-tunable white-light emission for NUV-WLEDs

摘要

A series of Dy~(3+) and Eu~(3+) co-doped Sr_3Gd(PO_4)_3 phosphors were synthesized by a high-temperature solid-state method. The crystal structure, optical band gap energy, luminescence properties, concentration quenching, energy transfer process and thermal stability were investigated. All the phosphors are pure eulytite-type Sr_3Gd(PO_4)_3 in structure. Under different wavelengths' excitation, the Sr_3Gd(PO_4)_3:Dy~(3+), Eu~(3+) phosphors exhibit different emission intensities for Eu~(3+) and Dy~(3+). The color and correlated color temperature (CCT) can be tuned from cool white to warm white by adjusting excitation wavelengths and the doping concentration of Eu~(3+). Under the 351-nm excitation, the optimal Sr_3Gd(PO_4)_3:0.03Dy~(3+), 0.085Eu~(3+) phosphor displays a warm white emission with CIE coordinate of (0.3987, 0.3613), CCT of 3409 K, internal quantum efficiency of 44.8% and activation energy of 0.1883 eV. These results suggest that single-phased white-emitting phosphors Sr_3Gd(PO_4)_3:Dy~(3+), Eu~(3+) can be used in the near-ultraviolet light-emitting diodes.