A Dual-Mode Optical Thermometer with High Sensitivity Based on BaAl₁₂O₁₉:Sm²⁺/SrAl₁₂O₁₉:Sm³⁺ Solid Solution Phosphors

A series of BaAl₁₂O₁₉:Sm²⁺/SrAl₁₂O₁₉:Sm³⁺ mixed-phase phosphors were produced in one step using the traditional high-temperature solid-phase process. Because Sm is divalent in BaAl₁₂O₁₉ and trivalent in SrAl₁₂O₁₉, the coexistence of Sm²⁺ and Sm³⁺ is realized in the mixed-phase host. Since the temperature sensitivity of Sm²⁺ and Sm³⁺ in the solid solution host is significantly different, this makes it possible for the sample to measure temperature based on the fluorescence intensity ratio (FIR). The crystal model, ion emission spectrum, and temperature sensitivity of these phosphors are studied in detail. Under the co-excitation of a 410 nm excitation source, this sample has excellent temperature measurement performance in the range of 313-513 K. Based on the FIR method, the maximum absolute temperature sensitivity (S_a) is 0.55 K^-1 at 513 K, and the maximum relative temperature sensitivity (S_r) is 2.47%K^-1 at 453 K. Moreover, based on the photoluminescence lifetime temperature measurement mode, the largest value of S_a at 413 K is 0.046 K^-1, and the maximum value of S_r at 473 K is 3.10%K^-1. In short, the BaAl₁₂O₁₉:Sm²⁺/SrAl₁₂O₁₉:Sm³⁺ solid solution is a kind of phosphor with nice temperature measurement ability, and it has very strong potential in the application of noncontact optical thermometers.