Papers by Keyword: Rare Earth Ion

Abstract: Four types of titanium dioxide (TiO₂) materials doped with a single kind of rare earth ions Ln³⁺ (Eu³⁺, Tb³⁺, or Sm³⁺) and three rare earth ions (Eu³⁺, Tb³⁺, and Sm³⁺) were synthesized by the sol-gel method. The compositions, structures, and photophysical properties of these compounds were tested. The structure of the rare earth ion-doped TiO₂ samples was characterized by X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Optical absorption and fluorescence information was obtained using UV-Vis spectroscopy and fluorescence spectroscopy. The surface morphology of rare earth ion-doped TiO₂ materials was observed using scanning electron microscopy (SEM). To further explore the photoluminescent properties of rare earth-doped TiO₂ materials for practical applications, small-scale LED light-emitting devices were fabricated.

Abstract: Lithium-rich layered oxide cathode materials have the advantages of a high voltage and a high specific capacity. Their commercial applications have however been impeded by some disadvantages such as low initial coulombic efficiency and low cycle life. To overcome these issues, rare earth ion-doped lithium-rich layered oxide cathode materials are investigated in this work. The irreversible release of O^2- in Li₂MnO₃ is suppressed by rare earth ions doping, which enhanced the initial coulombic efficiency of the materials. Meanwhile, the rare-earth ion radius used for doping is larger than the Mn⁴⁺ radius, which enlarges the (003)-crystalline plane spacing, resulting in a significant enhancement of the rate performance of the material.

Abstract: Two different BaTiO₃ (160nm) nanopowders coated with Y and with Dy were fabricated by an aqueous chemical coating method, and their dielectric properties and microstructures were investigated with X-ray diffraction, Impedance analyzer, SEM and TEM. Y and Dy were coated on the BaTiO₃ powder using nitrates. Coated BaTiO₃ powders were pressed in a disk shape and sintered at 1150~1200°C for 2 hours in reduced atmosphere of 10%H₂ - 90%N₂. Coating layer of the BaTiO₃ particle was thin with a thickness of 3 ~ 5nm. Coated BaTiO₃ sintered sample exhibited a larger lattice parameter (a, c) and smaller tetragonality (c/a) than pure BaTiO₃ one. Y coated BaTiO₃ sample sintered at 1200°C showed good dielectric properties with a high dielectric constant of around 2000 and a stable temperature coefficient of capacitance (TCC).

Abstract: The 91×91 complete energy matrix of 4f2 configuration ion Pr3+ in octahedral cubic crystal field has been constructed based upon the combination of Racah’s group-theoretical consideration with Slater’s wavefunctions. The energy levels of the neat hexachloride elpasolite crystals Cs2NaPrCl6 containing rare earth Pr3+ ion have been calculated. The results imply that the diagonalization to the complete energy matrix can be received as an effective method of performing a theoretical calculation to the rare earth compounds.

Abstract: A series of the Yb³⁺ -doped phosphate laser glass have been prepared under high temperature and different doping content and the fluorescence and absorption spectrum is observed, respectively. The influences of the Yb³⁺ -doped content on the spectral properties of the glass are analyzed and the optimal mole fraction is 4 %. The emission cross-section and fluorescent lifetime is calculated with McCumber theory. Furthermore, the integrated absorption cross-section, the full width at half maximum of the emission spectra and the laser performance parameters such as least particle count, saturation pump intensity and lowest pump intensity of Yb³⁺ -doped laser glass is calculated.

Abstract: The RE/Mn co-doped Co-Zn ferrites were prepared by the ceramic method. Infrared absorption and emission properties were obtained by investigating those ferrites. The IR spectra in the range from 400 to 1200 cm-1 were observed. Mainly, three bands were investigated. The high-frequency bands and low-frequency bands were assigned to the tetrahedral and octahedral complexes, respectively. The intensity of all the bands is found to increase while a decrease in broadness, which is explained on the cation distribution in the tetrahedral and octahedral sites were modified by RE/Mn addition. The Mn substitutes the Fe3+ and enters into the octahedral sites; while the partial RE3+ ions are apt to diffuse to the grain boundaries and others enter into the spinel lattice .This can be explained on the basis of ionic radii and ratios of the substituted cation. The results indicate that IR emissivity seems to be increasing with RE/Mn ratio within 8-14 μm wavebands. The maximum infrared emissivity is 0.968 when La/Mn ratio of 0.20 within 8-14 μm wavebands.

Abstract: A new electron trapping materials (ETM) SrS: Eu2+, Dy3+, which was prepared by the method of high temperature solid-state reaction. The results indicate that both ultraviolet light and visible light can be used as exciting source to store energy. After exposed under ultraviolet, the sample was stimulated by 980nm laser. As a result, an obvious luminescence at 615 nm was detected. The up-conversion emission spectrum was found to be a continuous broadband spectrum resulted from the multi-transitions of Eu2+ 4f6→4f7 (8S7/2). The emission peak intensity of SrS: Eu2+, Dy3+ was stronger than SrS: Eu2+.

Abstract: Nanoparticles of the wide band gap oxides doped with rare earth (RE) ions are prospective materials for application in optoelectronics as phosphors in a new generation of light sources. In this paper the mechanisms of the excitation of efficient 4f-4f intra-shell transitions in RE doped nanoparticles are discussed. These mechanisms either enhance the rate of host to impurity energy transfer or stimulate the intra-shell transitions of RE ions.

Abstract: Atomistic mechanisms that restrain diffusion of oxygen vacancies in BaTiO3 doped with rare earth ions as donors were analyzed using molecular dynamics simulation. It was confirmed that formation of cation vacancies and reduction of lattice volume are sources of resistance for the diffusion. The cation vacancies trap the oxygen vacancies at the nearby O2- sites by an attractive force associated with Coulombic interaction. In contrast, the rare earth ions repel the oxygen vacancies, which migrate via O2- sites, and accelerate the diffusion. This is one of the factors that determine the restraint behavior of the diffusion, which depends on the type of rare earth ion in BaTiO3-based materials.

Abstract: We report a model for the explanation of the single molecule magnet behavior of the [CuIILTbIII(hfac)2]2 cluster. The model takes into account the crystal field acting on the TbIII –ion and the exchange interaction between the TbIII and CuII ions. The energies of the low-lying levels are shown to increase with the decrease of the mean value of the z-projection of the total angular momentum of the cluster, thus forming a barrier for magnetization reversal that is in accordance with the experimental evidence.