A high-sensitivity dual-mode optical thermometry based on one-step synthesis of Mn2+:BaAl12O19–Mn4+:SrAl12O19 solid solution phosphors

Highlights: • The Mn²⁺:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solution realizes dual-mode thermometry. • The Mn²⁺:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solution has high temperature sensitivity. • The Mn²⁺:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solution avoids the defects of TCL. • The Mn^2+:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solution can be synthesized in one step. -- Abstract: Compared with rare earth ions, transition metals have high temperature sensitivity, but the research on thermometry according to only using transition metals were not mentioned in phosphors. In this regard, a series of Mn²⁺:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solutions were synthesized by high temperature solid phase method and researched. Although the sample is mixed phase, it can be synthesized in one step to avoid the defects in mixed phase preparation. The co-doping of Mn²⁺/Mn⁴⁺ is achieved by the self-reducing ability of BaAl₁₂O_19. It provides the possibility of thermometry doped Mn²⁺/Mn⁴⁺ based on the fluorescence intensity ratio. This material has excellent optical temperature sensing properties from 293 K to 406 K with good recyclability. Therefore, it is suitable for thermometry based on fluorescence intensity ratio with high maximum absolute (0.11 K⁻¹ at 406 K) and relative sensitivity (4.37% K⁻¹ at 293 K), obviously superior to the previously reported which are rare earth ions doped thermometry materials. Based on fluorescence lifetime of Mn⁴⁺, the maximum relative sensitivity is 4.48% K⁻¹ at 353 K. The Mn²⁺/Mn⁴⁺ co-doped material is reported for the first time. The Mn²⁺:BaAl₁₂O₁₉–Mn⁴⁺:SrAl₁₂O₁₉ solid solutions have broad application prospect in the field of fluorescence thermometry, and the dual-mode thermometry makes it has excellent applicability in all aspects.