Ambient- and calcination- temperature induced color-tunable upconversion luminescence in Yb3+/Er3+ co-doped Y2(MoO4)3 phosphors for optical thermometer

Simultaneous Thermal Enhancement of Upconversion and Downshifting Luminescence by Negative Thermal Expansion in Nonhygroscopic ZrSc(WO4)2PO4:Yb/Er Phosphors

“…To investigate the temperature sensing behavior of the ZSWP:25% Yb/1% Er phosphor, the temperature-related fluorescence intensity ratio (FIR) of green UC emission from 2 H 11/2 / 4 S 3/2 → 4 I 15/2 transitions is shown in Figure a. It is obvious that the FIR values increase rapidly with an increase in temperature in the range of 298–573 K. On the basis of the previous reports, the relative population of the thermally coupled energy levels ( 2 H 11/2 / 4 S 3/2 ) obeys the Boltzmann law and the FIR of two green UC emissions can be expressed as , FIR = I 1 I 2 = n 1 n 2 = g 1 w 1 δ 1 g 2 w 2 δ 2 exp ⁡ − Δ E k T = B exp true( − normalΔ E k T true) where I 1 and I 2 represent the integrated green UC emission intensities for the thermally coupled 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions, respectively. In general, n , g , ω, and δ represent the number of ions, the degeneracy, the angular frequency, and the emission cross section of fluorescence transitions ( 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 ), respectively.…”

“…To investigate the temperature sensing behavior of the ZSWP:25% Yb/1% Er phosphor, the temperature-related fluorescence intensity ratio (FIR) of green UC emission from 2 H 11/2 / 4 S 3/2 → 4 I 15/2 transitions is shown in Figure 8a. It is obvious that the FIR values increase rapidly with an increase in temperature in the range of 298−573 K. On the basis of the previous reports, the relative population of the thermally coupled energy levels ( 2 H 11/2 / 4 S 3/2 ) obeys the Boltzmann law and the FIR of two green UC emissions can be expressed as 45,46 (2)…”

Giant enhancement of anti-quenching upconversion luminescence in Sc2W3O12:Er3+/Yb3+ phosphors for temperature sensing

“…A 21-fold enhancement of green luminescence in Yb 1.98 Er 0.02 Mo 3 O 12 microcrystals was achieved from 313 to 573 K. 7 Green upconversion luminescence was selectively thermally enhanced 54-fold from 298 K to 523 K in Y 2 Mo 3 O 12 :Yb 3+ / Er 3+ phosphors. 8 In Er 3+ /Yb 3+ co-doped Sc 2 W 3 O 12 phosphors, the overall upconversion luminescence intensity at 753 K was 74.5 times higher than that at room temperature. 9 Unfortunately, in order to obtain strong upconversion luminescence, the excitation power still needs to be maintained at a high level (2-3 W cm À2 ).…”

Tailoring thermal expansion and luminescence thermometric performance of KMgScW3O12-based compounds

“…Liao et al studied the luminescence properties of Sc 2 Mo 3 O 12 :Yb 3+ /Er 3+ and explained that the thermally enhanced UC emission is mainly controlled by the ET from Yb 3+ to Er 3+ at 298–473 K and then by the radiation transition of Er 3+ above 473 K. 33 Huang et al explained that the formation of a Yb-MoO 4 dimer leads to the tunable ET process of Yb 2 Mo 3 O 12 :Yb 3+ /Er 3+ . 34 Wei et al reported that the Frenkel defect formed via controlled annealing of Sc 2 (WO 4 ) 3 :Ln (Ln = Yb, Er, Eu, Tb, and Sm) can work as an energy reservoir and back-transfer the stored excitation energy to Ln 3+ upon heating. 35 Nevertheless, the investigation on the thermal enhancement of UC emission as well as its corresponding mechanism in rare-earth ion doped NTE compounds is still not sufficient and the connection between NTE intensity and luminescence intensity is not clearly stated.…”