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

Figure 1

(a) XRD patterns of the as-prepared NaLuF₄:6%Er³⁺, % Sr²⁺ (, 5, 10, 18, 25, 30) microcrystals. The vertical black lines are the standard profiles of β-NaLuF₄ (JCPDS 27-0726) and SrF₂ (JCPDS 86-2418). (b) FWHM of the 31.2° peak vs. content of Sr²⁺ ions. (c) The enlarged view at °. (d) Variation trend of the -axis length and cell volume of the β-NaLuF₄:6%Er³⁺ samples doped with different Sr²⁺ contents.

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