Charge Compensation-Directed Enhanced Photoluminescence in M+ (M = Li, Na, K) Co-Doped Novel Red Phosphor Ca2.5Hf2.5Ga3O12:Eu3+ for Lighting Applications

Against the backdrop of energy conservation and environmental protection, developing more stable and efficient phosphors has become an urgent challenge. In this study, we have synthesized a series of Ca2.5Hf2.5Ga3O12:Eu3+ (CHGO:Eu3+) red phosphors via a high-temperature solid-state method, which exhibit strong red emission at 610 nm under 394 nm excitation, corresponding to the 5D0→7F2 transition of Eu3+. To improve the lattice vacancies caused by charge imbalance when Eu3+ is doped into the CHGO lattice to replace Ca2+, we introduce the charge compensator M+ (M = Li, Na, K). The results of the emission spectrum show that the introduction of charge compensators can effectively improve the luminescence intensity. Among them, K+ has the most significant effect on increasing the emission intensity of Eu3+, making the emission intensity of the phosphor more than twice that when there are no charge compensation ions. Additionally, the quantum efficiency and thermal stability of these phosphors are significantly improved compared to the CHGO:0.075Eu3+ sample before substitution. At 423 K, the emission intensity of the CHGO:0.075Eu3+, 0.075K+ sample still remains at 88.7% of that at 298 K. The color rendering index of the prepared white LED is 81.2, and its CIE chromaticity coordinates are (0.3212, 0.3065). This indicates that the prepared CHGO:0.075Eu3+, 0.075K+ red phosphor has broad application prospects in solid-state lighting.