Broadly tunable emission from Ca₂Al₂SiO₇:Bi phosphors based on crystal field modulation around Bi ions

New non-rare-earth activated phosphors were discovered and have attracted much attention in the field of energy-efficient LED lighting. For instance Bi³⁺, when mixed into different matrix materials, can realize multiple luminescence intensities ranging from 400 to 700 nm. The tunable emission results from the susceptibility of bismuth naked 6s electrons to the crystal field surrounding Bi³⁺. In this work, we report the broadly adjustable emission of Bi³⁺ doped Ca₂Al₂SiO₇ phosphors by modifying the local environment around Bi³⁺. When M⁺ (M = Li, Na and K) is incorporated into the Ca₂Al₂SiO₇ lattice, the luminescence intensity is improved greatly. In addition, the position of the emission peak of Bi³⁺ shifts from 382 to 416 nm upon varying the relative ratio of B³⁺/Al³⁺/Ga³⁺ ions. The spectral red-shift behaviour is attributed to the enhancement of crystal field strength surrounding Bi³⁺. These results are promising for investigation of the luminescence properties of Bi³⁺.