Regulation of the luminescence of Bi 3+ -activated Ca 5 Ga 6 O 14 phosphors by varying doping concentration and composition design

Achieving the desired color temperature and color rendering index in light sources is challenging because of the deficiency of certain color components, notably cyan in the illumination spectra. In this investigation, we successfully synthesized orthogonal Ca 5 Ga 6 O 14 : Bi 3+ (CGO: Bi 3+ ) phosphors with space group Cmc21 , featuring two distinct Ca(1) and Ca(2) sites. Under the excitation of 335 nm, a broad cyan emission with a 495 nm peak was observed. Gaussian peak fitting revealed two sub-peaks at 445 and 500 nm, originating from the emission of Bi 3+ occupying Ca(1) and Ca(2) sites, respectively. As Bi 3+ doping concentration increased, the luminescence experienced a red shift, attributed to the cooperative impact of crystal field splitting and electron cloud rearrangement. Through the substitution of Sr 2+ ions, we achieved a 2.15 times enhancement in emission intensity and an increase in lifetime from 0.451 to 0.551 μs. This substitution also led to a consistent increase in the relative emission percentage of Bi(1) from 46.5% to 73.1%, while that of Bi(2) decreased from 70.5% to 44.9%. It is likely a result of some Bi 3+ ions originally situated in the Ca(2) site migrating to the Ca(1) site. Finally, the introduction of Na + ions for charge compensation resulted in a 20.18% increase in the luminescence intensity and an enhanced quantum efficiency of 84.21%. This CGO: Bi 3+ phosphor holds promise as a potential cyan phosphor for white light sources.