Oxalic Acid-Assisted Hydrothermal Synthesis and Luminescent of Hexagonal NaYF₄:Ln³⁺ (Ln = Sm, Eu, Yb/Er) Micro/Nanoplates

Figure 5

Schematic diagrams for the growth process based on the time-dependent experiments: (a) 1 h; (b) 4 h; (c) 8 h; (d-e) 12 h; and (f) 24 h.