Hydrothermal synthesis, electronic structure and tunable luminescence of single-phase Ca5(PO4)3F:Tb3+,Eu3+ microrods
Uniform and well-crystallized calcium fluorapatite [Ca5(PO4)3F, FAP] microrods have been successfully synthesized by a facile one-step hydrothermal synthesis method using sodium citrate as the crystal modifier. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), photoluminescent excitation spectra (PLE) and decay studies were employed to characterize the samples. The electronic structure and orbital population of FAP were also determined by means of density functional theory calculations. Under ultraviolet irradiation, the FAP:Tb3+,Eu3+ samples exhibit a blue-light emission of the host matrix, as well as the typical green emission band of the Tb3+ ions, and a red-light emission of Eu3+. The highly intense red emission bands of the Eu3+ ions were attributed to the effective energy transfer from the Tb3+ to Eu3+ ions, which has been justified through the luminescence spectra and the fluorescence decay dynamics. The luminescence colors of FAP:Tb3+,Eu3+ microrods can be easily tuned by changing the concentration of Eu3+ ions. The results reveal that the combination of the self-activated luminescence and rare earth-doping emission in FAP:Tb3+,Eu3+ microrods could result in tunable emission in a large color gamut, which can be used as a potential candidate for white-light-emitting diodes and other display devices.