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

Abstract

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 4F9/2 to the ground levels 6H15/2, 6H13/2 and 6H11/2 of Dy3+, respectively. The optimum doping concentration of Dy3+ was found to be about x = 0.05 for NaKLa1−xDyxNbO5 phosphors, and the critical distance of energy transfer among Dy3+ ions was calculated to be 17.45 A. The decay lifetime obtained for 4G5/2 → 6H13/2 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 NaKLa0.95Dy0.05NbO5 phosphor. The results showed that NaKLaNbO5:Dy3+ may be potential yellow-emitting phosphor applied in white light emitting diodes.