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

Figure 3

SEM images of Y₂O₃:Er³⁺-Yb³⁺ nanoparticles for different precipitant agents, (a) Urea, (b) Urea-LiOH, (c) Thiourea-LiOH, and (d) LiOH.

(a)

(b)

(c)

(d)