Optimization of upconversion luminescence performance and temperature sensing characteristics of Sr0.37Ba0.50Al2Si2O8:Ho3+, Yb3+ phosphors based on a cation substitution strategy

Upconversion luminescent (UCL) materials have broad application prospects in the field of temperature sensing; thus, improving the luminescence performance and temperature measurement sensitivity of upconversion phosphors is highly important. In this study, SrAl 2 Si 2 O 8 with good thermal stability was doped with Ho 3+ and Yb 3+ , and the optimal concentration was determined to be SrAl 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ (in mole fraction). A series of (Sr 0.87‒ x Ba x )Al 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ phosphor samples was prepared by using a cationic substitution strategy and further doping Ba 2+ to replace the Sr 2+ lattice in the matrix. The results show that the introduction of Ba 2+ effectively replaces Sr 2+ and significantly increases the upconversion fluorescence emission intensity of SrAl 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ by approximately 2.9 times. The temperature sensing properties of SrAl 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ and Sr 0.37 Ba 0.50 Al 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ were investigated. The Ho 3+ -based 5 F 5 and 5 S 2 / 5 F 4 nonthermal coupled energy level fluorescence intensity ratio (FIR) techniques in the Ba 0.37 Sr 0.50 Al 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ phosphors show a maximum temperature measurement absolute sensitivity of 4.32%/K at 573 K and a maximum relative sensitivity of 1.08%/K at 373 K; these values are 5.8 and 3.2 times greater, respectively, than that of the non-Ba 2+ -doped SrAl 2 Si 2 O 8 :1%Ho 3+ , 12%Yb 3+ phosphor. These results not only confirm the effectiveness of the cation substitution strategy in enhancing the upconversion luminescence performance and temperature sensing characteristics but also provide a scientific basis for the design of high-performance optical temperature sensors.