Effect of Bi3+ on fluorescence properties of YPO4:Dy3+ phosphors synthesized by a modified chemical co-precipitation method

Y0.99-xPO4:0.01Dy3+, xBi3+ (x=0, 0.01, 0.05, 0.10, 0.15, 0.20 and 0.25) phosphors have been synthesized by a modified chemical co-precipitation method using urea as a pH value regulator. The samples were characterized by X-ray powder diffraction (XRD) and photoluminescence spectroscopy. XRD results show that the samples have only single tetragonal structure when x≤0.15, but extraneous BiPO4 phase appears besides major tetragonal phase when x≥0.20. The crystallinity of the samples is found to improve with increasing Bi3+ ion concentration from 0 to 15 mol%, and then decreased for higher concentrations associated with increasing BiPO4 phase. Photoluminescence excitation spectra results show that the phosphor can be efficiently excited by ultraviolet light from 250 to 400 nm including four peaks at 294, 326, 352 and 365 nm. Emission spectra exhibit strong blue emission (483 nm) and another strong yellow emission (574 nm). When the Bi3+ ion concentration is 1 mol%, the intensity of excitation and emission spectra increased evidently. In addition, the yellow-to-blue emission intensity ratio (IY/IB) is strongly related to the excitation wavelength and not to the Bi3+ ion concentration. - Research highlights: → YPO4:Dy3+, Bi3+ was synthesized by chemical precipitation method using urea as pH value regulator. → Bi3+ can improve the luminescent efficiency of YPO4:Dy3+. → The phosphor has a broad excitation band from 250-400 nm including peaks at 294, 326, 352 and 365 nm. → The yellow-to-blue emission intensity ratio is related to the excitation wavelength not Bi3+.