Enhancement of Visible Upconversion Emission in Y₂O₃:Er³⁺-Yb³⁺ by Addition of Thiourea and LiOH in the Phosphor Synthesis

Figure 9

(a) Upconversion emission intensity versus excitation pump power at 980 nm, (b) dependence of the green and red upconversion emission for the Thiourea-LiOH sample.

(a)

(b)