Pumping-route-dependent concentration quenching and temperature effect of green up- and down-conversion luminescence in Er3+/Yb3+ co-doped Gd2(WO4)3 phosphors

Effects of Er 3+ concentration on down-/up-conversion luminescence and temperature sensing properties in NaGdTiO 4 : Er 3+ /Yb 3+ phosphors

“…The reason why the red emission at 980 nm excitation is much stronger is because the red emission level 4 F 9/2 can be easier populated under 980 nm excitation than that excited by 380 nm. In the case of 380 nm excitation, the 4 F 9/2 level is mainly populated via multiphonon relaxation from 4 S 3/2 level or radiative transition from upper levels and all of their rates are small, however, in the case of 980 nm excitation, 4 F 9/2 level can be populated by excitation state absorption and/or energy transfer from Yb 3+ and their rates can be much large [17]. Therefore, different features of luminescence were obtained in down-and up-conversion luminescence processes for the different excitation pathways and population routes.…”

Luminescence studies of Sm3+ single-doped and Sm3+, Dy3+ co-doped NaGdTiO4 phosphors

“…As is well known, the distances (R) between RE 3 þ ions become smaller with the increase of RE 3 þ concentration. And because the cross relaxation rates are inversely proportional to R Q , where Q represents the interaction mechanism between RE 3 þ ions, Q equals to 6, 8 or 10 for electric dipole-dipole (D-D), electric dipolequadrupole (D-Q), or electric quadrupole-quadrupole (Q-Q) interactions, respectively, the rates would be intensified greatly with the increase of RE 3 þ concentration, and then result in the decrease of the luminescence intensity at a certain RE 3 þ concentration [20].…”

Comparative study on upconversion luminescence and temperature sensing of α- and β-NaYF4:Yb3+/Er3+ nano-/micro-crystals derived from a microwave-assisted hydrothermal route

“…The populations of 2 H 11/2 and 4 S 3/2 fulfill the Boltzmann distribution law. The relationship between the FIR (R) of these two green emissions and temperature can be expressed as below [25] where I H and I S are the integrated intensities of the emissions for 2 H 11/2 -4 I 15/2 and 4 S 3/2 -4 I 15/2 transitions of Er 3 þ , respectively. C is a constant which is independent from the sample temperature but dependent on the spontaneous emission rate, degeneracy and photon energy.…”