Exceptional low-temperature fluorescence sensing properties in novel KBaY(MoO4)3:Yb3+,Ho3+ materials based on FIR of Ho3+ transitions 5F5(1) → 5I8/5S2 → 5I8

In this report, a series of novel KBaY(MoO4)(3):Yb3+,Ho3+ (KBYMO:Yb3+,Ho3+) materials with intense up-conversion (UC) luminescence properties were synthesized using a high-temperature solid-state reaction method. Upon 975 nm near infrared (NIR) laser excitation, KBYMO:Yb3+,Ho3+ mainly showed two emission bands at around 544 and 658 nm, as well as a feeble one at around 755 nm, corresponding to Ho3+ 5F4,S-5(2) -> I-5(8), F-5(5) -> I-5(8) and F-5(4),S-5(2) -> I-5(7) transitions, respectively. The UC luminescence mechanism in this kind of material was determined to be a two-photon process, including simultaneous energy transfer from Yb3+ to Ho3+. In order to explore its potential applications in low-temperature fluorescent thermometers, the temperature-dependent behavior (53-293 K) of KBYMO:0.60Yb(3+),0.01Ho(3+) as a representative was investigated in detail. Based on fluorescence intensity ratio (FIR) technology, the calculated FIR values of I-640/550 (F-5(5(1)) -> I-5(8)/S-5(2) -> I-5(8)) in KBYMO:0.60Yb(3+),0.01Ho(3+) (53-293 K) were adopted as the original data, which have been rarely used in previous systems. Therefore, the optimal absolute sensitivity S-a and relative sensitivity S-r were determined to be 0.0186 K-1 (233 K) and 31.45% K-1 (53 K), respectively, showing its potential as a key component material in low-temperature fluorescent thermometers.