Upconversion luminescence and Visible-Infrared Properties of β-NaLuF₄:Er³⁺ Microcrystals Synthesized by the Surfactant-Assisted Hydrothermal Method

Figure 2

SEM images of as-prepared microcrystals using different surfactants with different agents/Ln³⁺ molar ratio: (a) S1, (b) S2, (c) S3, (d) S4, (e) S5, (f) S6, (g) S7, (h) S8, and (i) S9. Insets are corresponding high magnification SEM images of the microstructures.

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