Photoluminescence and energy transfer of YAG: Ce³⁺, Gd³⁺, Bi³⁺

In this study, Gd³⁺ and Bi³⁺ ions act to redshift the emission band to orange region, and to enhance significantly the maximum emission of YAG: Ce³⁺. On account that size mismatch between the host and the doped Gd³⁺ ion, the crystal structure turns soft, and the emission spectra are not tuned from 540 to 570 nm but decreased the emission intensity. Accordingly, an effective way to increase emission intensity is to introduce Bi³⁺ ion into the YAG: Ce³⁺, Gd³⁺ phosphors. Experimental results show partial overlapping between the emission band of Bi³⁺ ion and the excitation band of Ce³⁺ ion, indicating that the energy transfer from Bi³⁺ to Ce³⁺ ions exists in the (Y_1.94Ce_0.06Gd)Al₅O₁₂: Bi³⁺ phosphor. Bi³⁺ ion can serve as the activator to provide energy for Ce³⁺ ion via cross relaxation phenomenon. Therefore, the (Y_1.94Ce_0.06Gd)Al₅O₁₂: Bi³⁺ phosphor could have potential applications in warm white LEDs.