Thermometry and up-conversion luminescence of Ln3+ (Ln = Er, Ho, Tm)-doped double molybdate LiYbMo2O8.

The discovery of stable and highly sensitive up-conversion (UC) phosphors using the fluorescence intensity ratio (FIR) is a significant challenge in the field of optical temperature sensor. Er³⁺/Ho³⁺/Tm³⁺-doped LiYbMo₂O₈ UC phosphors with excellent luminescence properties were successfully synthesized through a high-temperature solid-state reaction, and the crystal structure and UC luminescence properties were discussed in detail. The UC process has been investigated by spectra pump power dependence and further explained via the energy level diagram. All emission processes about Er³⁺ ions and Ho³⁺ ions are two-photon processes and the blue emission process about Tm³⁺ ions is a combination of two-photon process and three-photon process. Thermal sensing performances depended on FIR technology were estimated and the sensitivities of LiYb_1−xMo2O8:xLn³⁺ included absolute sensitivity (S_a) and relative sensitivity (S_r) can produce particular change rules with the temperature, which can serve as excellent candidates for applications in optical temperature sensing. With the increase of temperature, the maximum values of S_r of LiYb_1−xMo₂O₈:xLn³⁺ are 1.16% K⁻¹ (0.05Er³⁺), 0.25% K⁻¹ (0.01Ho³⁺), and 0.51% K⁻¹ (0.01Tm³⁺), respectively. In addition, the S_a value of LiYb_0.95Mo₂O₈:0.05Er³⁺ phosphor will reach the maximum (1.08% K⁻¹) at 475 K, while the maximum values of S_a of LiYb_0.99Mo₂O₈:0.01Ho³⁺ and LiYb_0.99Mo₂O₈:0.01Tm³⁺ are 0.16% K⁻¹, 0.14% K⁻¹. [ABSTRACT FROM AUTHOR]