Preparation and characterization of YAG microspheres doped with Eu2+/Eu3+ for broad band emission

Abstract

Achieving full-spectrum lighting is a major challenge for phosphor-converted light-emitting diodes (pc-LEDs), which are crucial for solid-state lighting. This study presents the synthesis of polycrystalline Eu-doped Y₃Al₅O₁₂ (YAG) phosphors through a sol-gel method and flame synthesis process, leading to XRD amorphous microspheres. The amorphous nature of the microspheres allows the reduction of Eu³⁺ to Eu²⁺ at a significantly lower temperature (800 °C) than the reduction of crystalline samples described in the literature (1400 °C). The presence of Eu²⁺ in the YAG lattice was confirmed by X-ray photoelectron spectroscopy (XPS). The X-ray diffraction (XRD) of samples annealed in reducing atmosphere confirmed partial crystallization of pure YAG in all examined samples. The Eu-doped YAG phosphor embedded in residual glass microspheres exhibited a broadband emission spectrum over the wavelength range 450–800 nm peaking at 565 nm, corresponding to the 4f⁶5d¹→ 4f⁷ electron transition within the Eu²⁺ ions.