Development of a novel yellow-emitting niobate phosphor for white light emitting diodes

In this work, novel yellow-emitting niobate phosphors NaKLaNbO₅:Dy³⁺ were synthesized via high temperature solid-state reaction. X-ray diffraction (XRD) and fluorescence spectroscopy measurements were used to investigate their crystal structures and photoluminescence properties. On account of XRD results, the as-expected phosphors were successfully prepared as single-phases and crystallized in tetragonal structure. Under excitation at 352 nm, the as-prepared phosphors presented three prominent emission peaks located at 481 (blue, weak), 579 (yellow, strong) and 671 (red, weak) nm, which were ascribed to the electronic transitions from the excited state ⁴F_9/2 to the ground levels ⁶H_15/2, ⁶H_13/2 and ⁶H_11/2 of Dy³⁺, respectively. The optimum doping concentration of Dy³⁺ was found to be about x = 0.05 for NaKLa_1−xDy_xNbO₅ phosphors, and the critical distance of energy transfer among Dy³⁺ ions was calculated to be 17.45 Å. The decay lifetime obtained for ⁴G_5/2 → ⁶H_13/2 transition of Dy³⁺ was very short (< 1 ms) and decreased with the increase in Dy³⁺ ion concentration. In addition, the temperature-dependent emission spectra were also investigated to explore the thermal stability of the concentration-optimized NaKLa_0.95Dy_0.05NbO₅ phosphor. The results showed that NaKLaNbO₅:Dy³⁺ may be potential yellow-emitting phosphor applied in white light emitting diodes.