Color-tunable emission in Ce3+, Tb3+co-doped Ca5(BO3)3F phosphor

Abstract

In this paper, Ce³⁺ doped and Ce³⁺, Tb³⁺ co-doped Ca₅(BO₃)₃F phosphors were synthesized by a high-temperature solid-state reaction. Upon excitation at 360 nm, the emission spectra of Ce³⁺ doped phosphors exhibit a broad emission band peaking at 392 nm, which originates from the 5d to 4f transition of Ce³⁺. The Ce³⁺, Tb³⁺ co-doped phosphors show strong energy transfer from Ce³⁺ to Tb³⁺, and the emission color can be tuned from purplish blue to green by changing the Tb³⁺ content. The excitation band in the 300–400 nm region broadens when monitored at 541 nm compared to that monitored at 392 nm. Furthermore, the co-doping of Tb³⁺ facilitates the appearance of green emitting Ce³⁺, which originates from Ce³⁺ on the Ca site other than that for purplish-blue Ce³⁺. The relationship between the luminescence properties of Ce³⁺ and its coordination environments, namely, different Ca sites, is discussed based on the calculations of centroid shift and crystal field splitting of 5d energy levels of Ce³⁺. Results suggest that Ce³⁺, Tb³⁺ co-doped Ca₅(BO₃)₃F phosphors may be a candidate for near-UV chip based white light-emitting diodes.