Dual-Color-Emitting α-Sr₂P₂O₇:Eu²⁺, Mn²⁺ Phosphors Prepared by Co-Precipitation Method for w-LED Applications

Undoped and Eu²⁺/Mn²⁺-doped strontium pyrophosphate phosphors (α-Sr₂P₂O₇ and α-Sr_1.84P₂O₇:0.04Eu²⁺/0.12Mn²⁺) were successfully prepared using a homogenous co-precipitation approach for detailed EPR-PL and crystal-field effects analysis. XRD confirmed that both samples crystallized in a single-phase orthorhombic structure, indicating long-range phase purity and the seamless integration of dopants into the host lattice without structural degradation. To investigate the subtle, localized structural distortions induced by the dopants, EPR spectroscopy was employed as a highly sensitive primary probe. The room temperature EPR spectrum revealed broad Mn²⁺ resonance lines and distinct low-field resonances for Eu²⁺, highlighting enhanced crystal-field interactions arising from the relatively low local symmetry at the substituted Sr²⁺ sites. Under UV excitation, the doped phosphor shows two sharp bands centered at 425 nm (blue) and 560 nm (yellow). Eu²⁺ acts as a sensitizer for Mn²⁺ in the phosphor lattice, thereby suggesting a potential energy transfer mechanism from Eu²⁺ to Mn²⁺. This opens a channel to tune the luminescence for possible white light generation through future concentration optimization and decay kinetics studies. These phosphors, with their luminescence and structural characteristics, have potential for color tunable white light-emitting diodes (w-LEDs) and other solid-state lighting applications.