A new and facile strategy to enhance the upconversion luminescence (UCL) emission of NaLuF₄: Er³⁺ microcrystals (MCs) using strontium (Sr) as a dopant has been reported. With the introduction of Sr²⁺, the products change from long NaLuF₄: Er³⁺ hexagonal microtubes to short hexagonal microtubes and finally to hexagonal microprisms. The growth mechanism is profoundly discussed according to the different reaction time-dependent morphologies. More importantly, the total fluorescence intensity is significantly reinforced by doping Sr²⁺ ions. When 18% Sr²⁺ is doped into NaLuF₄: Er³⁺ hexagonal microtubes, the maximum green and red luminescence intensities are about 5.8 and 4.4 times higher than those of Sr²⁺-free samples, respectively. The influences of Sr²⁺ ion doping content on the phase, the morphology, and the local crystal field symmetry of the as-synthesized NaLuF₄ crystals are investigated.

中文翻译：

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Sr2 +掺杂对β-NaLuF4：Er3 +六角形微管的形态学处理和上转换发光增强

已经报道了使用锶（Sr）作为掺杂剂来增强NaLuF ₄：Er ³⁺微晶（MCs）的上转换发光（UCL）发射的新的简便策略。随着Sr ²⁺的引入，产品从长NaLuF ₄：Er ³⁺六角形微管变为短六角形微管，最后变为六角形微棱镜。根据不同的反应时间相关形态，深入讨论了生长机理。更重要的是，通过掺杂Sr ²⁺离子可以显着增强总荧光强度。将18％Sr ²⁺掺杂到NaLuF _4中时：Er ³⁺六角形微管的最大绿色和红色发光强度分别比不含Sr ^2+的样品高约5.8和4.4倍。研究了Sr ²⁺离子掺杂含量对合成的NaLuF ₄晶体的相，形貌和局部晶体场对称性的影响。