Optical temperature sensing properties of a phosphor mixture of Sr2Mg3P4O15:Eu2+ and SrB4O7:Sm2+

In this work, a mixture of a Eu2+-doped phosphor (Sr2Mg3P4O15:Eu2+) and a Sm2+-doped phosphor (SrB4O7:Sm2+), noted as ESMix, was prepared to investigate its fluorescence intensity ratio (FIR) for the use of temperature sensing. Temperature-dependent luminescence of ESMix were measured under 365 nm excitation and the blue band emission of Eu2+. (centered around 450 nm) together with the orange band emission of Sm2+ (centered around 580 nm) were observed to have different trends with the change of temperature. FIR between the blue band and the orange band were proved to have high sensitivity from 380 K to 700 K. This method may be a promising FIR-type optical thermometry using divalent rare earth (RE) ions whose emissions are broad bands which is different from traditional FIR scheme using trivalent RE ions whose emissions are sharp peaks. Changing peaks into bands makes ESMix insensitive of peak shift and has great potential of reducing the requirements on the instruments thus saving costs.