Precipitation Synthesis and Color-Tailorable Luminescence of α-Zr(HPO₄)₂: RE³⁺(RE = Eu, Tb) Nanosheet Phosphors

The rare earth (RE = Eu and Tb) ions-doped α-Zr(HPO₄)₂ (ZrP) nanosheet phosphors were synthesized by direct precipitation method, and their structures and photoluminescence properties were investigated. The results of X-ray diffraction and scanning electron microscopy indicated that the systems of ZrP:RE³⁺ had similar nanosheet structure except with relatively larger interlayer spacing as compared with pure α-ZrP. Under the excitation of UV light, the ZrP:RE³⁺ nanosheet phosphors showed red and green emission peaks corresponding to the ⁵D₀→⁷F₂ transition of Eu³⁺ and the ⁵D₄→⁷F₅ transition of Tb³⁺, respectively. After Eu³⁺ and Tb³⁺ were co-doped in ZrP host, not only the red and green emission peaks were simultaneously observed, but also the luminescent intensity and fluorescence lifetimes of Tb³⁺ were gradually decreased with the increase in Eu³⁺-doping concentration, which implied the energy transfer from Tb³⁺ to Eu³⁺ happened. It was deduced that the energy transfer from Tb³⁺ to Eu³⁺ occurred via exchange interaction. Through optimization to the samples, a nearly white-light emission with the color coordinate (0.322, 0.263) was achieved under 377 nm excitation. The ZrP:RE³⁺ nanosheet phosphors may be a potential color-tailorable candidate for fabricating optoelectronic devices such as electroluminescence panels.