Luminescence and energy transfer of LuTaO4:Bi3+,Ln3+ (Ln = Sm, Eu) phosphors for non-contact optical thermometry

Even though fluorescence intensity ratio-based non-contact temperature measures have been extensively studied due to their high sensitivity and fast response time, novel efficient luminescent materials are still important for the development of temperature measurement applications. Herein, we report a series of novel LuTaO₄:Bi³⁺,Ln³⁺ (Ln = Sm, Eu) temperature sensing phosphors and conduct a detailed study of the crystal structure, optical properties and temperature sensing properties. At the 284 nm excitation, Bi³⁺ emits near-ultraviolet light at 385 nm. The introduction of Ln³⁺ ions into LuTaO₄:Bi³⁺ has been demonstrated to facilitate an effective energy transfer from the Bi³⁺ to the Ln³⁺ ions. In addition, Bi³⁺ and Ln³⁺ ions exhibit significantly different thermal quenching behaviors. The absolute sensitivity (S_a) and relative sensitivity (S_r) of the prepared phosphor were evaluated by FIR method within the temperature span of 303–513 K, and the highest relative sensitivity was observed to be 2.76%K⁻¹ (LuTaO₄:0.005Bi³⁺,0.03Sm³⁺) and 2.09%K⁻¹ (LuTaO₄:0.005Bi³⁺,0.003Eu³⁺). In addition, it was also observed that LuTaO₄:Bi³⁺,Eu³⁺ phosphors had obvious different color behaviors at different temperatures. These findings demonstrate that LuTaO₄:Bi³⁺,Ln³⁺ phosphors exhibit outstanding temperature sensing performance, showing great potential for future applications in FIR-based non-contact temperature measurement technology.