Luminescent Thermometer Systems Dy³⁺/Eu³⁺ and Tb³⁺/Sm³⁺ Based on Coordination Compounds: New Pairs to the Approved Tb³⁺/Eu³⁺?

Abstract

2′,3′-h]-quinoxaline) with good thermal stability up to 446 °C. Statistical substitution of Sm 3+ , Tb 3+ , Gd 3+ , and Dy 3+ with a second Ln 3+ ion led to [Ln 1−x Ln′ x (MeDPQ) 2 Cl 3 ] solid solutions, which exhibit temperature-dependent luminescent properties. Their visible emission and intensity ratios of transitions vary with temperature in the range of 253−353 K. In the case of the composition [Tb 1−x Eu x (MeDPQ) 2 Cl 3 ], the maximum relative thermal sensitivity S r values were determined as 3.77% K −1 , 3.97% K −1 , and 3.97% K −1 for x(Eu 3+ ) = 0.01, 0.05, and 0.1, respectively. The compositions [Dy 1−x Eu x (MeDPQ) 2 Cl 3 ] and [Tb 1−x Sm x (MeDPQ) 2 Cl 3 ] also showed significant performance. For the pair Dy 3+ −Eu 3+ , the S r values were determined as 3.88%K −1 , 3.91% K −1 , and 3.80% K −1 for x(Eu) = 0.01, 0.05, and 0.1, respectively. For the pair Sm 3+ −Tb 3+ , the S r values are 3.28% K −1 and 3.82% K −1 for x(Sm) = 0.9 and 0.1, respectively. The largest thermal sensitivity value S r of 4.11% K −1 was achieved for the composition [Gd 0.8 Tb 0.18 Eu 0.02 (MeDPQ) 2 Cl 3 ]. In addition, patterns of thermometric performance are bound to the energy transfer efficiency Tb 3+ → Eu 3+ , Dy 3+ → Eu 3+ → Dy 3+ , and Tb 3+ → Sm 3+ , as this characteristic is strongly temperature-dependent in the studied range.