Temperature sensing based on fluorescence intensity ratio (FIR) technique is one of the application fields of upconversion (UC) luminescence materials. 1-4 Lanthanide ions with two thermally coupled energy levels (TCLs), such as Er 3+ , Ho 3+ , and Tm 3+ , are widely adopted as FIR signals. 5-7 Among them, Er 3+ ion is the preferred ion due to its suitable energy gap (700-800 cm −1) of TCLs (2 H 11/2 / 4 S 3/2) and higher UC quantum efficiency. 8 Yb 3+ ion is often introduced as a sensitizer to enhance the UC emission intensity, and the application of Yb 3+ and Er 3+ co-doped UC luminescence materials in temperature sensing field attracts much attention in recent years. 9-11 Sensitivity (S A) is an
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