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

Abstract

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 Ho^{3+ 5}F₄,⁵S₂ → ⁵I₈, ⁵F₅ → ⁵I₈ and ⁵F₄,⁵S₂ → ⁵I₇ 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:0.60Yb³⁺,0.01Ho³⁺ as a representative was investigated in detail. Based on fluorescence intensity ratio (FIR) technology, the calculated FIR values of I_640/550 (⁵F₅₍₁₎ → ⁵I₈/⁵S₂ → ⁵I₈) in KBYMO:0.60Yb³⁺,0.01Ho³⁺ (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.