Microwave-assisted hydrothermal synthesis, temperature quenching and laser-induced heating effect of hexagonal microplate β-NaYF4: Er3+/Yb3+ microcrystals under 1550 nm laser irradiation

Up-conversion luminescence, temperature sensing properties and laser-induced heating effect of Er3+/Yb3+ co-doped YNbO4 phosphors under 1550 nm excitation

“…With an increase of sample temperature, the non-radiative relaxation rate of the emitting levels, the energy transfer probability originating from the emitting levels, and the crossover process between the emitting levels of the luminescent centers and the charge transfer band of them or the absorption band of the matrix in high energy region will be enhanced, which will result in the quenching of the luminescence intensity. Similar to our previous research results, the non-radiative relaxation process would be the main mechanism for the temperature dependent UC luminescence quenching of Er 3+ in the present case 16,25 . In addition, it can also be found that the peak positions of them almost unchanged but the relative intensity and the changing trend of each green UC emission are different with an increase of temperature.…”

“…The possible CR processes are shown in Fig. 5 25 . As can be seen, CR1-CR4 processes are responsible for the depopulation of the green emitting levels 2 H 11/2 and 4 S 3/2 , but CR5 and CR6 processes take the responsibility for the depopulation of the red emission level 4 F 9/2 , which will cause the quenching of the corresponding green and red UC emissions, respectively.…”

“…As can be seen, the two green emission bands originated from 2 H 11/2 , 4 S 3/2  →  4 I 15/2 transitions can be observed, and the overall luminescence intensity decreases with an increase of temperature, indicating temperature dependent luminescence quenching occurs. Generally, non-radiative relaxation, energy transfer and crossover process are the main three reasons which may cause the temperature quenching of luminescence 16,25 . With an increase of sample temperature, the non-radiative relaxation rate of the emitting levels, the energy transfer probability originating from the emitting levels, and the crossover process between the emitting levels of the luminescent centers and the charge transfer band of them or the absorption band of the matrix in high energy region will be enhanced, which will result in the quenching of the luminescence intensity.…”

“…Previously, we have investigated the spectroscopic properties of Er 3+ mono-doped YNbO 4 phosphor and obtained the optimum Er 3+ concentration (5 mol%) 22 . According to our previous results 16,25 , two sets of YNbO 4 : Er 3+ /Yb 3+ phosphors were prepared by a traditional high-temperature solid-state reaction method. In one set, the concentration of Er 3+ was fixed to be 5 mol%, and the doping concentrations of Yb 3+ were designed to be 0, 2, 6, 10, 14, 16 and 20 mol%.…”

“…In addition to 980 nm excitation, the Er 3+ can also be excited by 1550 nm. 1550 nm laser has obtained considerable attention due to its eye-safe nature and wide applications in optical communication and solar cells; meanwhile, it is also an effective excitation source to investigate the UC luminescence properties of RE 3+ -doped materials 23–25 . It is reported that efficient UC emission from Er 3+ was obtained under monochromatic excitation around 1500 nm 24 .…”