Realizing a broad-scope and high-sensitivity optical thermometer based on dual-emission centers with structure confinement effect-related energy transfer

Abstract

Developing optical temperature sensors with superior performance has become an important but challenging task owing to the increasing temperature monitoring demand under extreme conditions. Herein, for developing luminescence materials with high performance, the energy transfer processes and temperature-dependent photoluminescence properties of Ce³⁺- and Mn²⁺-activated K₇CaLn₂B₁₅O₃₀ (Ln = Lu, Y, Gd) phosphors were comparatively analyzed. On the basis of K₇CaLn₂B₁₅O₃₀ (Ln = Lu, Y, Gd) hosts with a compacted Ce³⁺–Mn₂⁺ distance of approximately 3.3 Å, an energy transfer process with high efficiency was achieved by a structural confinement effect. Energy transfer efficiency values between Ce³⁺ and Mn²⁺ in the three co-doped systems were in the order η_ET(KCLBO) > η_ET(KCYBO) > η_ET(KCGBO), which could be attributed to the different distances between Ca²⁺ and Ln³⁺. Arising from the different local site environments of Ce³⁺ and Mn²⁺, the tendency of the photoluminescence thermal stability of Ce³⁺ and Mn²⁺ in the three co-doped systems is different. Owing to the diverse sensitivity that Ce³⁺ and Mn²⁺ have toward temperature with a faster luminescence dropping rate of Mn²⁺ than that of Ce³⁺, a broad-scope optical thermometer based on fluorescence intensity ratio (FIR) was designed. Finally, the optimal relative sensitivity was found to be 3.045% K⁻¹ (at 160 K), and the corresponding temperature resolution was 0.1 K among the three co-doped systems. The resulting spectral adjustability and distinguished sensitivity of the systems based on the site environments of reference and signal ions shed light on the design and development of luminescence materials with high sensitivity for optical temperature sensing.