Luminescence properties and electronic structure of Ce3+\mathrm{Ce^{3+}}-doped gadolinium aluminum garnet

Yttrium-gadolinium aluminum garnets (YGdAG) doped with Ce3+ ions have been prepared by co-precipitation method. The luminescent properties of Ce3+ ions in Gd3(1−x)Ce3xAl5O12 (х = 0.01) have been studied upon excitation in the 2–20 eV region. The substitution of Gd3+ for Y3+ in the garnet structure results in broadening the emission band and shifting its maximum towards the longer wavelengths. It was found that in addition to the 4f → 5d excitation bands of Ce3+ ions, the excitation spectra for the Ce3+ emission contain bands at 6.67, 7.75, and 9.76 eV. These bands are attributed to the Ce3+-bound exciton formation and O 2p → Al 3s, 3p transitions, respectively. Although gadolinium states dominate near the bottom of the conduction band of Gd3Al5O12, contributions from Altetr and Aloct atoms to the conduction-band density of states are evaluated as quite essential

Luminescence Properties of Solid Solutions of Borates Doped with Rare-Earth Ions

The structural and luminescence properties of Lu x Y1 − x BO3 solid solutions doped with Ce3+ or Eu+3 have been investigated. It has been found that the solid solutions crystallize in the vaterite phase with a lutetium concentration x < 0.5. For a higher lutetium concentration x, the solid solutions contain an additional calcite phase with a content less than 5 wt %. The luminescence spectra are characterized by intensive impurity emission under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that, as the lutetium concentration x in the Lu x Y1 − x BO3: Ce3+ solid solutions increases, the emission intensity smoothly decreases, which is associated with a gradual shift of the Ce3+ 5d(1) level toward the bottom of the conduction band, as well as with a decrease in the band gap. It has been established that, in the Lu x Y1 − x BO3: Eu3+ solid solutions with intermediate concentrations x, the efficiency of energy transfer to luminescence centers increases. This effect is explained by the limited spatial separation of electrons and holes in the solid solutions. It has been demonstrated that the calcite phase adversely affects the luminescence properties of the solid solutions

Luminescence of Borates with Yttrium and Lutetium Cations

This paper reports on the results of an investigation into the luminescence properties of yttrium and lutetium borates, as well as the Y0.35Lu0.65BO3 solid solution, under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that there exists an intrinsic luminescence band in the ultraviolet spectral range 260–270 nm due to the luminescence of self-trapped excitons. It has been found that the kinetic characteristics of this band depend on the density of the exciting synchrotron radiation. A number of luminescence bands have been observed in the long-wavelength range due to the presence of defects in the crystal structure of borates. It has also been shown that the energy transfer to impurity centers has a recombination nature and can also occur through impact ionization of defects. It has been revealed that, for the solid solution, the excitation efficiency of the luminescence of defects increases under interband excitation, which can be associated with the limited separation of the components of an electron-hole pair as a result of short-range order disturbance in the structure of the solid solution

Luminescence properties of solid solutions LuxY1−xPO4:Eu3+\mathrm{Lu_xY_{1-x}PO_4:Eu^{3+}}

Solid solutions Lu$_x$Y$_{1-x}$PO$_4$ doped with Eu$^{3+}$ were synthesized by the sol-gel method. Luminescence spectra under UV and X-ray excitation and luminescence excitation spectra in the UV-VUV energy range are presented. Observed variations of the structure of 4f-4f Eu3+ lines with the composition of the solid solution are explained by the fluctuations in the distribution of substitutional cations. The role of electronic structure modification in the fundamental absorption region with changing Y/Lu ratio is discussed and is suggested as the origin of different efficiency of energy transfer to Eu$^{3+}$ in this region. Temperature dependence of the luminescence yield is related to the competition between emission centers and traps