Lanthanide upconversion luminescent materials featuring multi-peak and tunable emissions allow for ratiometric luminescence thermometry in a remote detection manner. However, wide explorations are still required to develop relevant materials for efficient thermometric performances. Herein, Yb/Er co-doped non-stoichiometric analogues of bismuth oxyfluoride were obtained by simply tuning the F/(Bi + Ln) molar ratio of the reactants in a solid-state reaction method, for the first time. We achieved simultaneous regulations in composition, structure, morphology, and upconversion luminescence properties of BiOF:Yb/Er (2/1 mol%) microcrystals. Compositional analysis revealed not only the predictable increase of fluorine content, but also the constant O/(Bi + Ln) atomic ratios in all nominal BiOF:Yb/Er. Experimental results showed the structure and morphology evolutions from hexagonal-phase micro-flowers, to tetragonal-phase microplates, and further to orthorhombic-phase irregular microcrystals. Benefiting from adjustable composition, structure and morphology, up-conversion luminescence with adjustable intensity and color was obtained. Temperature dependent upconversion properties and ratiometric thermometric performances based on the thermally coupled levels, H and S of Er, were explored. BiOF:Yb/Er, BiOF:Yb/Er, and BiF:Yb/Er microcrystals were found as suitable temperature sensing candidates with operating temperature range as wide as 298−673/723 K, high relative sensitivity up to 1.24% K, and minimum temperature uncertainty of 0.15 K. These results benefit not only further explorations for high-performance lanthanide-based luminescence thermometers, but also the chemistry of fluorides made from the solid-state reaction method.

中文翻译：

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BiOxFy:Yb/Er微晶的成分、结构、形貌和上转换发光的同时演化及其在比率温度传感中的应用

具有多峰和可调发射特性的镧系元素上转换发光材料允许以远程检测方式进行比率发光测温。然而，仍需要广泛探索来开发具有高效测温性能的相关材料。在此，首次通过固相反应方法简单调节反应物的F/(Bi + Ln)摩尔比，获得了Yb/Er共掺杂的氟氧化铋非化学计量类似物。我们实现了 BiOF:Yb/Er (2/1 mol%) 微晶的成分、结构、形貌和上转换发光特性的同时调控。成分分析不仅揭示了氟含量的可预测增加，而且还揭示了所有标称 BiOF:Yb/Er 中恒定的 O/(Bi + Ln) 原子比。实验结果显示了从六方相微花到四方相微板，再到斜方相不规则微晶的结构和形态演变。得益于成分、结构和形貌的可调，获得了强度和颜色可调的上转换发光。探索了基于热耦合水平、Er 的 H 和 S 的温度依赖性上转换特性和比率测温性能。 BiOF:Yb/Er、BiOF:Yb/Er 和 BiF:Yb/Er 微晶被发现是合适的温度传感候选材料，其工作温度范围宽达 298−673/723 K，相对灵敏度高达 1.24% K，并且最小温度不确定度为0.15 K。这些结果不仅有利于高性能稀土基发光温度计的进一步探索，而且有利于固态反应方法制备氟化物的化学。