Photoluminescence properties and energy level of RE (REÂ =Â Pr, Sm, Tb, Er, Dy) in Y4Si2O7N2

Energy level scheme showing the 4f ground states of the trivalent (filled square) and divalent ions (filled circle) and lowest energy 5d states of the trivalent (open square) and divalent ions (open circle) relative to the valence and conduction band of Y4Si2O7N2. The red dashed horizontal line is the optical band gap of Y4Si2O7N2. The arrows (1-4) indicate the experimentally determined transitions used to construct this scheme.179