Papers by Keyword: Ytterbium

Abstract: Ho³⁺/Yb³⁺ co-doped ZnO-TiO₂ composite system were synthesized by powder-solution mixing method and their upconversion (UC) luminescence characteristics were investigated under the 980 nm laser excitation. The effect of various ZnO/TiO₂ mixing ratios, and Ho³⁺ and Yb³⁺ concentrations were also studied. The XRD patterns showed that the product fired at 1300 °C consisted of Zn₂TiO₄, TiO₂, RE₂Ti₂O₇, and RE₂TiO₅ (RE = Ho³⁺ and/or Yb³⁺) phases. The green emission centered at 538 nm wavelength was detected as the strongest emission intensity which it was in accordance with the ⁵F_4, ⁵S₂ → ⁵I₈ transition of Ho³⁺ ion. The emission intensity of the product changed by varying ZnO/TiO₂ mixing ratios, and Ho³⁺ and Yb³⁺ concentrations. Brightest UC emission was observed in the sample of 1ZnO:1TiO₂ (in mole) doped with 0.03 mol% Ho³⁺, 9 mol% Yb³⁺ fired at 1300 °C for 1 h. Besides, the dependence of the UC emission intensity on the excitation power indicated that the two-photon process was responsible for this UC system.

Abstract: In the present work the influence of co-doping with ytterbium ions (for 0, 0.5, 1.5, 2.5 wt.% of Yb³⁺) on physical properties of 8/65/35 PLZT was studied. The ceramic powders were synthesized by the modified sol-gel method, and underwent consolidation by the pressure-less sintering techniques, in Ts=1200°C/6h. Our investigations give a detailed account of the relationships between concentrations of trivalent ytterbium ions in PLZT matrix, on their structure, microstructure, as well as luminescence properties. Near-infrared luminescence spectra at about 1020 nm were registered, which correspond to ²F_5/2 - ²F_7/2 transition of Yb³⁺. Based on decay measurements, the luminescence lifetimes for the ²F_5/2 excited state of Yb³⁺ were determined. Luminescence decay analysis indicates that the ²F_5/2 lifetime increase with increasing activator concentration (Yb³⁺) in PLZT ceramic matrix.

Abstract: The method for Lu determination in Yb preparations enriched in 176Yb by atomic and emission spectrometry with inductively coupled plasma (AES-ICP) is reported. The relative determination error from 0.0001 to 0.1% of Lu mass is less than 40%.

Abstract: To promote the alcohol catalytic oxidation of Pd/C catalysts, it was implemented that the lanthanide Yb was introduced to the catalyst via the precipitation thermal decomposition and chemical reduction methods. The structure analysis and surface morphology of Pd-Yb/C catalysts were investigated by XRD and SEM. The ethanol electrocatalytic oxidation activity of in alkaline media was studied by cyclic voltammetry. The results show that the performance of ethanol catalytic oxidation on Pd-Yb/C electrode is better than that on the Pd/C electrode. The introduction of Yb can promote Pd/C catalytic oxidation alcohol and its poisoning tolerance ability.

Abstract: In the present work, Cerium Fluoride (CeF₃) was selected as the host material because of its High density, fast response and high radiation resistance, efficient absorption and energy transfer by host (to activator). Rare earths have been used to show the process of Quantum Cutting (QC) via energy transfer process between Tb³⁺ and Yb³⁺ incorporated in CeF₃. For the synthesis of CeF₃ nanoparticles codoped with Tb³⁺ and Yb³⁺ ion, co-precipitation route was employed. Different doping concentrations were prepared to study the changes that take place in the luminescence spectra of the composition. Thus, concentration dependent study of the fluorescence of CeF₃: Tb³⁺, Yb³⁺ was carried out. These materials have great applications in solar cell devices as quantum efficiencies up to 200 % can be achieved.

Abstract: To increase efficiency of continuous 1.5 μm laser radiation crystal laser media should be used instead of the glass ones. Generation efficiency in major laser crystals with ytterbium and erbium is at a disadvantage in relation to phosphate glasses. A cause of this phenomenon is a reverse energy transfer. Could be found crystals comparable in efficiency with Yb-Er phosphate glasses At present a number of investigations on the use of ions relaxators Се 3+ in crystals Ca2Al2Si07 with ytterbium and erbium have been carried out to solve the problem of the reverse energy transfer in crystals [1,2]. It has been determined [1-3] that high content of cerium is needed to depress the reverse energy transfer. But cerium and ytterbium are in different ends of a lanthanide series, so silicate crystals with more isomorphic capacity such as Yb,Er,Ce:CaGdSiO (CGCS) have been proposed [3]. A sufficient solubility of Се 3+ ions in these crystals gives fast excitation relaxation on a laser level and guards against the reverse energy transfer from Er3+ to donor ions. Furthermore, a number of crystal media on the base of borate crystals with a developed phonon spectrum have been proposed [4,5]. They lack the reverse energy transfer, fast multiphonon nonradiative relaxation shunts the 4I11/2 – 4I13/2 Er3+ transfer. New crystals on the base of anhydrous borates – calcium-yttrium oxyorthoborates - Ca4YO(BO3)3 (YCOB) with ytterbium appeared recently [6], which showed high efficiency of generation, as well as calcium-barium fluor-orthoborates YbEr:Ca BaFBO3 (CBFB), in which ytterbium ions formed centers of luminescence with excellent characteristics [6]. Unfortunately, erbium ions in YCOB are characterized by high three level parameter [6], therefore the efficiency of generation Er,Yb:YCOB is not high. It has been determined recently that erbium ions in crystals CBFB have outstanding spectroscopic parameters, besides, between ytterbium and erbium ions fast energy transfer of electronic excitation takes place [7]. Since the efficiency of a sensitized laser medium depends on joint characteristics of the Yb and Er centres and the efficiency of their interactions, then available data allow considering crystals CBFB as a considerably promising matrix for an effective 1.5 μm laser. In order to obtain the most promising laser crystals and to answer the question cited above, it should be made their comparative analysis on basic spectroscopic and generative parameters. One of the important parameters related directly to the efficiency of the laser medium is an energy density of the generation threshold. Given spectroscopic parameters of active centers in crystals, the generation threshold of the one-activated laser medium (in an idealized model without passive losses) with a tree-level or quasi-four-level scheme of generation is specified by properties of active centers and can be easily determined by a simple formula [8]. The results obtained by this method are often used for determination of limiting parameters of the three-level laser media, the ytterbium media, for instance, and their comparative analysis [8]. There are known calculations of sensitized media generation parameters, among them the ytterbium-erbium glasses with a tube pumping [9], which although can be used for a diode pumping, nonetheless they are too unwieldy for simple estimation and comparative analysis. Hence there is a demand for simple analytical expressions such as [8] to calculate the lower limit of generation of the sensitized two-activated laser media with a diode pumping. The work reports the growing of single crystals CBFB and YCOB doped with erbium and ytterbium with erbium, and single crystals Yb,Er,Ce:CGS as well. We have made a comparative analysis of an ytterbium-erbium media for 1.5 μm lasers with a diode pumping on the base of simple expressions for limiting generation thresholds of the idealized sensitized media with a three-level scheme of generation, obtained in the approximation of balance equations without considering nonlinear and cumulative processes.

Abstract: Ytterbium doped laser glasses is generally preferred in the updating of various laser material because it have excellent mechanical and stability of thermal and optical properties. In this paper, experiments are performed through changed the concentrations of laser glasses medium and Ytterbium ions based on current research. The different of the concentrations and thickness of Yb3+ doped phosphate glasses have been investigated in order to gain best spectroscopic properties and stability of thermal and optical properties.

Abstract: The precipitation hardening response of as-cast Mg-8Yb-0.5Zr magnesium alloy was investigated in the present work. The microstructure evolution of the alloy illustrated that Mg2Yb intermetallic phase was dissolved by solution heat treatment at 520°C for 12 hours. An apparent precipitation hardening response in Mg-8Yb-0.5Zr was discovered after artificial aging at 150°C, with maximum hardness increment of about 80 percent at the peak condition. It was found that the precipitates of the alloy were in the shape of two conjoined cosh and globe about 50 nm, and precipitated preferentially on grain boundaries and dislocations.

Abstract: A wood-based Ni-P coating electromagnetic shielding material was prepared in an ytterbium oxide-added electroless plating bath. The kinetic model was established and confirmed to be in accord with the experiment and can be used to predict the deposition rate within a certain range. The experimental results showed that the Ni-P coating prepared with the addition of Yb₂O₃ were smoother, denser and brighter than that prepared without addition of Yb₂O₃. The deposition rate and electromagnetic shielding effectiveness of the former were 2.662mol×10^-4/(cm²h) and 56.48 dB which is about 13% and 9% higher than those of the latter under the same bath compositions and operation conditions.

Abstract: Polycrystalline ytterbium-doped barium cerate with composition BaCe0.95Yb0.05O3- has been fabricated by solid state reaction. The compound has an orthorhombic perovskite structure and a fine and homogeneous grain size distribution, with a mean value of 0.4 m. The creep behavior was studied by means of constant crosshead-speed compression tests in air at temperatures of up to 1300 °C. At the lower strain rates and higher temperatures, the material deformed by grain boundary sliding; the corresponding true stress-true strain curves displayed an initial strength drop followed by an extended steady state stage. A continuous transition towards a brittle regime was observed with increasing initial strain rate and/or decreasing temperature.