Tm3+/Yb3+ co-doped SrF2 up-conversion phosphors for non-invasive optical thermometry: ratiometric approach using thermal and non-thermal coupled fluorescent emission bands

To explore novel up-conversion (UC) system for optical temperature sensing, a series of Tm/Yb:SrF2 fluoride powders were fabricated employing a combustion synthesis (CS) technique. When Tm/Yb:SrF2 samples were excited by near-infrared radiation (similar to 980 nm), four UC emission bands at similar to 477 nm ((1)G(4) -> H-3(6)), similar to 649 nm ((1)G(4) similar to F-3(4)), similar to 700 nm (F-3(2),3 -> H-3(6)) and similar to 771 nm (H-3(4) similar to H-3(6)) were observed. Non-contact thermal sensing performances based on temperature-dependent fluorescence intensity ratio (FIR) technique of thermally and non-thermally coupled energy levels were estimated in the range from 298 to 573 K. The co-doped phosphor showed, at 298 K, a maximum relative sensitivity S-NTr of similar to 2.2%K-1 for the non-thermally coupled energy levels [(H-3(4) -> H-3(6) )/ ((1)G(4) -> H-3(6))] and a maximum relative sensitivity S-r of similar to 1.7%K-1 for the thermally coupled levels [(F-3(2),3 -> H-3(6))/(H-3(4) -> H-3(6))]. These outcomes show a good temperature-sensing performance when the nonthermally coupled levels with different temperature dependences were selected as the thermometric parameters. Hence, the Tm/Yb: SrF2 UC system has a promising prospect as optical temperature-sensing material.

Automated summary

A series of Tm/Yb:SrF2 fluoride powders were fabricated by combustion synthesis for optical temperature sensing, showing good performance and promising prospects for applications.