Morphology Manipulation and Upconversion Luminescence Enhancement of β-NaLuF₄: Er³⁺ Hexagonal Microtubes via Sr²⁺ Doping

Figure 2

SEM images of β-NaLuF₄:6Er³⁺ MCs doped with Sr²⁺ at different concentrations. (a–f) Refer to 0, 5, 10, 18, 25, and 30%, correspondingly. (g–l) Are corresponding high-resolution SEM images of the microstructures, and insets are TEM images.

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