Designing dual‐mode optical thermometer based on Ca 3 Sn 2 SiGa 2 O 12 :Bi 3+ ,Eu 3+ phosphor

Abstract Growing demands for precision temperature sensing drive substantial progress in optical thermometric technologies. In this work, Bi 3+ ,Eu 3+ co‐doped Ca 3 Sn 2 SiGa 2 O 12 (CSSG) samples exhibiting excellent temperature measurement performance were successfully synthesized via solid‐state reaction. Systematic investigations for structure, luminescent properties, and energy transfer from Bi 3+ to Eu 3+ of CSSG:Bi 3+ ,Eu 3+ were elucidated. Upon 303 nm excitation, CSSG:Bi 3+ ,Eu 3+ can emit broadband from Bi 3+ ions (near ultraviolet light) and sharp lines from Eu 3+ ions (red light) due to ET between Bi 3+ and Eu 3+ . Leveraging different thermal quenching rates of emission of Bi 3+ and Eu 3+ , dual‐mode optical thermometry relied on fluorescence intensity (FI, emission of Bi 3+ ), and FI ratio (FIR, emission of Bi 3+ and Eu 3+ ) was designed. Maximum values of relative sensitivities are 0.98% K −1 for FI mode (398 K) and 0.74% K −1 for FIR mode (360 K). These findings validate CSSG:Bi 3+ ,Eu 3+ as a robust candidate for noncontact thermometry.