Multicolor tunable Bi3+,Sm3+ co-doped Sr2GdGaO5 phosphor and its application in optical thermometry

Non-contact temperature measurement is gaining widespread attention for its broad temperature range, rapid response, and minimal thermal inertia. However, the spectral peak position modulation, the sensitivity, and reliable promotion remain crucial challenges. Herein, a novel Sr2GdGa0.4Al0.6O5:Bi3+,Sm3+ phosphor with excellent luminescence performance for optical thermometry was developed based on a cation-substitution strategy. By introducing various Al3+ ions, the emission peak of Bi3+ ions could be controlled and shifted from 472 to 461 nm. Besides, the emission positions of the Bi3+ ions and the co-doped Sm3+ ions exhibited a distinct separation, enabling effective signal differentiation for temperature detection. Additionally, an impressive 52% energy transfer from Bi3+ to Sm3+ was realized in the Sr2GdGa0.4Al0.6O5:Bi3+,Sm3+ phosphor. Moreover, owing to the variant external electronic configuration, Bi3+ and Sm3+ ions displayed diverse sensitivity to the temperature with a faster dropping rate with Bi3+ ions compared to that for Sm3+. According to the thermal quenching responses of Bi3+ and Sm3+ ions between 303 K and 563 K, a temperature-detection performance was achieved based on the fluorescence intensity ratio (FIR), where Bi3+ ions were used as detection signals and Sm3+ ions as reference signals. The achieved maximum absolute sensitivity (S-a) and relative sensitivity (S-r) were 0.028 K-1 (@543 K) and 1.222% K-1 (@484 K), respectively, surpassing most current optical thermometric materials. Furthermore, the thermochromic features presented by the designed phosphors enabled a qualitative assessment of the ambient temperature. The acquired spectral adjustability and high sensitivity based on the cation-substitution strategy described in the present study can provide an effective pathway for the development of excellent optical thermometry materials.