Achieving Eu²⁺ Luminescence at Trivalent Lattice Site in Rb₃Y(PO₄)₂:Eu toward Multicolor Emissions by Carbon and Hydrogen Coreduction

The advancement of Eu 2+ ‐activated luminescent materials tailored to exhibit a range of properties is crucial for addressing the specific demands of various application fields. However, the lack of suitable lattice sites in numerous compounds for stable Eu 2+ incorporation restricts their potential for diverse optical properties. Herein, a facile strategy of carbon and hydrogen coreduction utilizing graphite crucibles is proposed to effectively achieve the impressive luminescence of Eu 2+ at trivalent Y sites in Rb 3 Y(PO 4 ) 2 :Eu phosphors. Rb 3 Y(PO 4 ) 2 :Eu exhibits blue‐violet emission when Eu 2+ predominantly occupies the Rb1 and Rb2 sites. Inspiringly, by facilitating the reduction of more Eu 3+ to Eu 2+ , a yellow emission band at 550 nm arising from Eu 2+ at Y sites emerges, enabling the realization of single‐component white‐emitting and yellow‐emitting Rb 3 Y(PO 4 ) 2 :Eu phosphors. The diverse luminescent properties of Rb 3 Y(PO 4 ) 2 :Eu expand its potential applications in different white light source devices and optical thermometry. This work presents an innovative synthetic strategy to develop remarkable Eu 2+ luminescence at trivalent cation sites, thereby broadening the optical properties of the material and enabling multifunctional applications.