Dysprosium doped novel apatite-type white-emitting phosphor Ca9La(PO4)5(GeO4)F2 with satisfactory thermal properties for n-UV w-LEDs

A novel apatite structure phosphor Ca9La(PO4)5(GeO4)F2:Dy3+ (CLPGF:Dy3+) with a hexagonal lattice in the P63/m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy3+ phosphor can absorb in the UV-vis spectral region of 290-475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The concentration quenching of Dy3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4F9/2 to 6H15/2 transition and 4F9/2 to 6H13/2 transition of Dy3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy3+ phosphor is a promising white-emitting candidate for w-LEDs applications.