Designing dual-emission phosphors for temperature warning indication and dual-mode luminescence thermometry

Color tunable phosphors of Mn⁴⁺ and Tb³⁺ co-doped double-perovskite SrGdLiTeO₆ (SGLT) were synthesized in this work. The crystal parameters and photoluminescence performances were investigated in detail. By taking advantage of the different thermal quenching strengths between Mn⁴⁺ and Tb³⁺ ions, the emission color of SGLT:0.7%Mn⁴⁺/1%Tb³⁺ changed from red to green, which could be used for high-temperature temperature warning indication. Moreover, according to the luminescence intensity ratio (LIR) technique, wide temperature-range optical thermometry was developed and further, the maximum relative sensitivity (S_R1) value of the SGLT:0.7%Mn⁴⁺/5%Tb³⁺ phosphor was determined to be 1.49% K^-1 at 560 K. On the other hand, the sensing properties were also analyzed based on the temperature-dependent lifetime method. The most interesting thing is that the maximum S_R2 value reached 1.88% K^-1 at 573 K. This work proved that the Mn⁴⁺ and Tb³⁺ co-doped double-perovskite SrGdLiTeO₆ could be potentially used in temperature warning indication and high sensitivity luminescence thermometry.