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Lutetium oxide nanocrystals codoped with Tm3+ and Yb3+ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3+, Yb3+ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3+ is above 0.2%. The optimal Tm3+ and Yb3+ doped molar fractions are 0.2% and 2%, respectively. The strong blue (490 nm) and the weak red (653 nm) emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+, respectively. Power-dependent study reveals that the 1G4 levels of Tm3+ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH− groups and the enlarged nanocrystal size.

In this paper, the Czochralski growth, absorption spectra, and photoluminescence spectra of Nd:GdVO 4 crystals are studied. From its absorption spectra, Nd:GdVO 4 is found to exhibit an anisotropic optical absorption effect, and its effective Judd–Ofelt parameters are calculated: Ω 2 =10.281×10 −20 cm 2 , Ω 4 =5.426×10 −20 cm 2 and Ω 6 =9.943×10 −20 cm 2 . By these parameters, the absorption oscillator strengths, emission oscillator strengths, transition probabilities, fluorescence branch ratios, energy lifetimes, and integrated emission cross-sections are also derived. The photoluminescence spectra of Nd:GdVO 4 crystal consist of a wide emission band of host and the characteristic emission bands of Nd 3+ . Based on the excitation spectrum, both the two evident peaks locating at 345 and 371 nm are ascribed to the characteristic excitation of Nd 3+ , and an energy transfer from the host to its doping Nd 3+ ions is indicated.

The cubic-ZrO2 (100) ‖ NiO (111) interface provides an opportunity for comparison between atomic-scale measurements, atomistic simulations, and theoretical electronic structures. High-resolution electron microscopy indicates that the oxides share a common oxygen layer and that the small lattice strain is largely taken up by NiO near the interface. Using simple Coulomb plus Buckingham-type interatomic potentials, we are able to provide a more focused picture, revealing two types of boundary. The lowest energy interface is highly planar, almost ideal in structure; there is a second interface, of higher energy, that shows a rumpled structure with strain taken up by deformation of nickel chains. Depth profiling of atomic site energies permits calculation of interface versus bulk and surface energies, and it shows that the interface effects penetrate only two to three atomic layers. Embedded cluster density functional studies of bulk and interface-region sites permit the characterization of perturbations of electronic density around the boundaries.

Samples of Y2O3:1%Er were prepared by coprecipitation method and the pH value of precipitant ammonium bicarbonate was adjusted by ammonia. Results of Fourier transform infrared spectra (FTIR) and elemental analysis showed that the chemical construction of precursors at pH range of 8.0-9.5 had little change. By X-ray fluorescence spectrometer (XRF) and scanning electron microscope (SEM) analysis, it was found that the pH value of precipitant had a significant impact on the content of erbium in precursor and it can influence particle size as well as its distribution of the products, both of which had important effects on the luminescent properties of the products.

The precursor powders of LuAG : Ce3+ transparent ceramics were synthesized by solvo-thermal method. The crystal structure and morphology of powders were analyzed by means of Fourier transform infra-red spectroscopy, X-ray diffraction and scanning electron microscopy. The precursor powders were sintered into transparent ceramics in vacuum and then in nitrogen without any additive. The surface morphology of the transparent unpolished ceramics was characterized using scanning electron microscopy. Some factors that affect the transparency of ceramics were discussed. The UV-Vis fluorescence excitation and emission spectra of LuAG : Ce3+ transparent ceramics were measured. The vacuum ultraviolet spectra of transparent ceramics were investigated using the synchrotron radiation as the excitation source. The excitation mechanism of Ce3+ was discussed at different excitation wavelength.

Energy levels, densities of states, electronic densities, electrostatic interaction integral parameters F k and spin-orbit coupling parameters ζ 4f for ZnS: Tm 3+ are calculated self-consistently, using both one-electron local density discrete variational non-relativistic Hartree-Fock-Slater (HFS) and relativistic Dirac-Slater (DS) cluster models. In these calculations, both spin-restricted and spin-polarized models are considered. The finite clusters calculated include TmS 4 and TmS 4 Zn 12 clusters for cubic ZnS, which are embedded in the crystal environment. The spin-orbit coupling parameter ζ 4f derived from DS cluster calculations is equal to 2689 cm -1 , rather near the result of the relativistic Hartree-Fock free ion model. The parameters F k and ζ 4f are further calculated from the 4f radial wave function obtained by solving the HFS and the DS atomic equations. It is shown that by decreasing the effective exchange-correlation potential, these parameters can be reduced to approximately match empirical values. A comparison of the excited energy level scheme of ZnS:Tm derived from the calculated parameters and the experimental spectra is presented.

Energy levels, density of states (DOS), and electronic densities for ZnS: Tm 3+ were calculated self-consistently, using both nonrelativistic Hartree-Fock-Slater (HFS) and relativistic Dirac-Slater (DS) one-electron local- density spin restricted or polarized cluster models. The L-S coupling parameter ζ(4f) and electrostatic integrals F(k) were calculated. Luminescence transitions obtained using the intermediate coupling method are compared with experiment.