Molten‐Salt‐Assisted Synthesis of Na₃Bi(PO₄)₂:Eu³⁺ Nanoparticles with Strong Red Emission

Single phase Eu³⁺‐doped Na₃Bi(PO₄)₂ (NBPO) nanoparticles with different Eu³⁺ concentrations are successfully synthesized by a molten‐salten method using Na₃PO₄ · 12H₂O both as reaction medium and as reactant. The influence of synthesis conditions such as the Na₃PO₄ · 12H₂O content, heating temperature, and time on the crystal structure of the final products is investigated by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). It reveals that pure phase Na₃Bi(PO₄)₂ nanoparticles with size about 100 nm are successfully achieved when the mixture (molar ratio of 1:4 between Bi(NO₃)₃ · 5H₂O and Na₃PO₄ · 12H₂O) is heated at 180 °C for 12 h. After Eu³⁺‐doping, NBPO:Eu³⁺ nanoparticles exhibit bright red emission peaking at 620 nm under the excitation of the near ultraviolet (NUV) light. The luminescence is attributed to the electric dipole transition ⁵D₀ → ⁷F₂ of Eu³⁺ ions. The luminescent intensity of the NBPO:Eu³⁺ phosphors is strongly dependent on the Eu³⁺ content and concentration quenching occurred when the Eu³⁺ concentration is larger than 8 mol%, which is attributed to dipole–dipole interaction. This work provides a green way for the synthesis of phosphate‐based nanomaterials and suggests that Eu³⁺‐doped Na₃Bi(PO₄)₂ has a great potential application in the lighting and display fields.