White upconversion luminescence in CaF2:Yb3+/Eu3+ powders via the incorporation of Y3+ ions

White upconversion luminescence (UCL) was achieved under 980 nm excitation in the CaF2:Yb3+/Eu3+ material using Y3+ to adjust the luminescence performance. In this luminescent system, Yb3+ not only plays the role of a sensitizer of Eu3+, but also generates green fluorescence from Yb3+ dimers (2-Yb3+) by cooperative transitions in the CaF2 matrix. One of the primary colors of green corresponds to the 2-Yb3+ cooperative emission exactly. Eu3+ acts as an activator for emitting red and blue fluorescence simultaneously. Interestingly, the color of the UCL can be controlled by adjusting the doping concentration of Y3+ ions, and white UCL was realized when the concentration of Y3+ was 1%.