Structural and Bluish-White Luminescent Properties of Li⁺-Doped BPO₄ as a Potential Environmentally Friendly Phosphor Material

Many efforts have been devoted to exploring novel luminescent materials that not contain expensive or toxic elements, or do not need a mercury vapor plasma source. In this paper, BPO₄ and Li⁺-doped BPO₄ powder samples were prepared by the Pechini-type sol−gel (PSG) process. The structure and optical properties of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence (PL) excitation and emission spectra, kinetic decay, and X-ray photoelectron spectra (XPS), respectively. It was found that PSG -derived Li⁺-doped BPO₄ annealed at 960 °C exhibited bright bluish-white emission centered at 416 nm. The luminescence decay curves analysis indicates that each sample has two kinds of lifetimes (5.9 ns and 0.529 ms) and two types of kinetic decay behaviors which can be fitted into a single-exponential function and a double-exponential function, respectively. This can be attributed to two kinds of emission centers in samples. The luminescent mechanisms of the samples are discussed in detail.