Influence of gallium content on Ga3+ position and photo- and thermally stimulated luminescence in Ce3+-doped multicomponent (Y,Lu)3GaxAl5-xO12 garnets

Abstract

Photoluminescence, thermally stimulated luminescence (TSL) and EPR characteristics of the Ce 3+ -doped single crystals of multicomponent Y1Lu2GaxAl5-xO12 and Lu3GaxAl5-xO12 garnets with different Ga contents (x = 0, 1, 2, 3, 4, 5) excited in the Ce 3+ -related absorption bands are investigated in the 9 -500 K temperature range. The distribution of Ga 3+ and Al 3+ ions in the crystal lattice is determined by the NMR method. The relative number of Ga 3+ ions in the tetrahedral crystal lattice sites, the maxima positions of the TSL glow curve peaks and the corresponding trap depths are found to decrease linearly with the increasing Ga content. At the same time, the reduction of the activation energy Ea of the TSL glow curve peaks creation under irradiation in the 4f -5d1 absorption band of Ce 3+ is strongly nonlinear. To explain this effect, the suggestion is made that Ea is the energy distance between the excited 5d1 level of Ce 3+ and a defect level located between the 5d1 level and the bottom of the conduction band and arising from the Ga 3+ ion perturbed by the nearest neighboring Ce 3+ ion. The electrons thermally released from the excited Ce 3+ ions are suggested to be trapped at the perturbed Ga 3+ ions resulting in the appearance of electron Ga 2+ centers. In spite of the fact that the paramagnetic Ga 2+ ions were not detected by EPR, the described above process was found for Fe 3+ impurity ions, namely the electron transfer from the 5d1 excited levels of Ce 3+ to Fe 3+ was directly detected by EPR.

Luminescence Spectroscopy and Origin of Luminescence Centers in Bi-Doped Materials

“…Therefore, it could also depend on the band gap energy E g of the host material and increase with increasing E g [154]. The best materials to investigate these dependences could be multicomponent garnets where both the CB edge energy and E g can be changed by variation of their composition (see, e.g., [194][195][196][197][198][199]). Let us consider some examples.…”

“…It was shown that the incorporation of the Ga 3+ ions results in a strong reduction of the band gap edge (by 1 eV from Y 3 Al 5 O 12 :Bi to Y 3 Ga 5 O 12 :Bi). In [195][196][197][198][199], it was shown that the increasing Ga content also results in a drastic decrease of the CB bottom energy in different Ce 3+ -doped multicomponent garnets. The presence of two-UV and VIS-emission bands in Y 3 Al 5 O 12 :Bi with the close lowest-energy excitation bands indicates that the triplet RES of Bi 3+ should be located close to the bottom of CB of Y 3 Al 5 O 12 [7].…”

Peculiarities Related to Er Doping of ZnO Nanorods Simultaneously Grown as Particles and Vertically Arranged Arrays

“…However, there was no EPR signals in the ZnO:Er(1%) NRA. Considering the EPR spectrometer sensitivity reaching about 10 12 spins (see Experimental Section) and the signal-to-noise ratio, practically, the concentration of spins, which could be reliably detected, is about tens of ppm . Therefore, one may expect the Er concentration to be lower than that in the NRF sample.…”

Pressure -induced changes in the persistent luminescence of Gd2.994Ce0.006Ga3Al2O12 and Gd2.964Ce0.006Dy0.03Ga3Al2O12 nanoceramics

“…However, since changes in the persistent luminescence were observed with the increase in sintering pressure, the electron transfer through the conduction band should also be taken into account, where the distance from the trap depends on the pressure applied in the preparation process. In this case, the electrons excited from the ground level to the 5d state due to the relatively small thermal activation energy 43 are transferred through the conduction band to the traps (3). The activation energies ( E a(lp) and E a(hp) ) calculated from the TL glow curves were in the range of 0.58 to 0.69 eV (below the CB), which show that these defects are able to capture and release the electrons at room temperature.…”