Effect Of Yb Research Articles

Three- and two-photon upconversion luminescence switching in Tm3+/Yb3+-codoped sodium niobate nanophosphor

Intense infrared-to-visible upconversion (UC) emission in Tm 3+ /Yb 3+ -codoped sodium niobate (NaNbO 3 ) nanocrystals under resonant excitation at 976 nm is presented. The results showed that by increasing the pump power/intensity, a strong reduction is observed at the 800/480 nm emitted intensity ratio, characterizing what can be denominated as laser pump power-induced color tunability or luminescent switching. The physical origin is discussed with a focus on tailoring of luminescent switchers to operate at a large pump power range and, indeed, it is intrinsically associated with the competition of the two- and three-photon UC processes and with highly efficient UC emissions in the investigated material. The effect of Yb 3+ -ion concentration along with the theoretical aspects on luminescence switching has been investigated. The results obtained here could be useful in the field of sensors and networks for optical processing and optical communications.

Role of Yb and Si on the precipitation hardening and recrystallization of dilute Al–Zr alloys

The effect of Yb and Si on precipitation hardening and recrystallization of Al–Zr alloys have been investigated. The results show that Yb is more effective than Si to accelerate the precipitation kinetics and stimulate the precipitation of Al–Zr alloy. The peak hardness values for the Al–Yb–Si–0.08Zr are 510MPa and 515MPa after isochronal aging to 425°C and isothermal at 350°C for 200h, respectively, which are significantly larger than that of the Al–Yb–Zr and Al–Si–Zr alloys. The precipitates in alloys with addition of Zr are more thermally stable than that of the Al–Yb alloy. The recrystallization temperatures of Al–Zr, Al–Si–Zr, Al–Yb–Zr and Al–Yb–Si–Zr alloys are 250, 400, 425 and 450°C, respectively, increase with the increase of the corresponding peak aging hardness. The recrystallization temperature of Al–Yb alloy is 325°C, which is much lower than that of the Al–Yb–Zr alloy due to the coarsening of the Al3Yb at temperature larger than 300°C.

Effects of Yb:KYW thin-disk femtosecond laser ablation on enamel surface roughness

This study aimed to quantitatively evaluate the surface roughness of enamel following ablation with a Yb:KYW thin-disk femtosecond pulsed laser at different fluences (F), scanning speeds and scanning line spacings. Thirty human extracted teeth were sectioned into crowns and roots along the cementum–enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick. The samples were randomly divided into ten groups (n=3). Samples of groups 1–8 were irradiated with a femtosecond pulsed laser. These enamel samples were fixed on a stage at focus plane, and a laser beam irradiated onto the samples through a galvanometric scanning system, with which rectangular movement could be achieved. Samples of groups 9 and 10 were prepared with grinding instruments. Following ablation and preparation, the samples were examined for surface roughness with a three-dimensional laser profile measurement microscope. The results showed that scanning speed and scanning line spacing had little influence on the surface roughness of femtosecond pulsed laser-ablated enamel, except when F=4 J/cm2. When a lower fluence was used, the enamel surface roughness was higher, and vice versa. This study showed that various laser fluences, scanning speeds and scanning line spacings can affect and alter enamel surface roughness. Therefore, adequate parameters should be chosen to achieve the proper therapeutic benefits.

Visible green upconversion luminescence of Li+/Er3+/Yb3+co-doped CaWO4phosphor and effects of Yb3+concentration

The upconversion (UC) luminescence of <TEX>$Li^+/Er^{3+}/Yb^{3+}$</TEX> co-doped <TEX>$CaWO_4$</TEX> phosphors and effects of <TEX>$Yb^{3+}$</TEX> concentration are investigated in detail. Single crystallized <TEX>$CaWO_4$</TEX> : <TEX>$Li^+/Er^{3+}/Yb^{3+}$</TEX> phosphor can be obtained, co-doped up to 35.0/5.0/30.0 mol% (<TEX>$Li^+/Er^{3+}/Yb^{3+}$</TEX>) by solid-state reaction. Under 980 nm excitation, <TEX>$CaWO_4$</TEX> : <TEX>$Li^+/Er^{3+}/Yb^{3+}$</TEX> phosphor exhibited strong green UC emissions visible to the naked eye at 530 and 550 nm induced by the intra 4f transitions of <TEX>$Er^{3+}$</TEX> (<TEX>$^4H_{11/2}$</TEX>, <TEX>$^4S_{3/2}{\rightarrow}^4I_{15/2}$</TEX>). The optimum doping concentrations of <TEX>$Yb^{3+}$</TEX> that would result in the highest UC luminescence were determined, and a possible UC mechanism that depends on the pumping power is discussed in detail.

Blue upconversion luminescence in 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals

The effect of Yb 3 + concentration on the fluorescence of 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals is investigated. Under the excitation of 980 nm laser, the strong blue (477 nm) emission band is observed and attributed to 1G 4 → 3H 6 of Tm 3 + . The ratio of blue to red emission increases with the increasing of Yb 3 + and remains constant at 10 mol% Yb 3 + . The pump dependence and upconversion mechanisms show that the two-photon cooperative upconversion process is responsible for the enhancement of the blue upconversion emission. The Commission Internationale de l'eclairage chromaticity coordinates (x, y) illustrate that the 12 CaO·7 Al 2O 3:1 mol% Tm 3 + /10 mol% Yb 3 + can emit high-purity blue light.

Up conversion luminescence of Yb 3+–Er 3+ codoped CeO 2 nanocrystals with imaging applications

The effects of Yb 3+ doping on up conversion in Yb 3+–Er 3+ co-doped cerium oxide nanocrystals are reported. Green emission around 545 and 560 nm attributed to the 2H 11/2, 4S 3/2→ 4I 15/2 transitions and red emission around 660 and 680 nm due to 4F 9/2→ 4I 15/2 transitions under 975 nm excitation were studied at room temperature. Both green and red emission intensities increase as the Yb 3+ concentration increases from 0%. Emission strength starts to decrease after the Yb 3+ concentration exceeds a critical amount. The green emission strength peaks around 1% Yb 3+ concentration while the red emission strength peaks around 4%. An explanation of competition between different decay mechanisms is presented to account for the luminescence dependence on Yb 3+ concentration. Also, the application of up converting nanoparticles in biomedical imaging is demonstrated.

Effects of Yb and Zr microalloying additions on the microstructure and mechanical properties of dilute Al–Sc alloys

It is known that Zr and Yb partition to the Al3Sc precipitates created during aging when microalloyed separately in dilute binary Al–Sc alloys. Addition of Zr delays precipitate coarsening, thereby improving the coarsening resistance of the ternary Al-Sc-Zr alloys. Addition of Yb increases the resistance against dislocation climb, thereby improving the creep resistances of the ternary Al-Sc-Yb alloys. A combination of microhardness, creep, and atom probe tomography measurements provide evidence that these effects of Zr and Yb additions are cumulative in quaternary dilute Al–Sc–Yb–Zr alloys: Yb increases their creep resistance at 300°C compared with ternary Al–Sc–Zr alloys and Zr improves their coarsening resistance at 300°C compared with ternary Al–Sc–Yb alloys. Additionally, excellent coarsening resistance is observed at 350 and 375°C.

Threshold characteristics analysis of one-end-pumped Yb 3+-doped gain-guided and index-antiguided fiber laser

An exact analytical expression of the threshold pump power for the one-end-pumped Yb 3+-doped gain-guided and index-antiguided (GG–IAG) fiber laser has been obtained by solving the improved rate equations (REs) with the additional leakage losses. The effects of Yb 3+ concentration, fiber length, core radius and mirror reflectivity on the threshold pump power are discussed. After optimizing, the results show that the laser threshold of GG–IAG fiber laser can be greatly reduced while maintaining single mode oscillation. Compared to the numerical methods, the analytical expression has easy calculation and distinct results.

Single electron transfer-living radical polymerization of methyl methacrylate catalyzed by ytterbium powder

Zerovalent ytterbium (Yb) powder is firstly used as a catalyst in single electron transfer-living radical polymerization of methyl methacrylate initiated by carbon tetrachloride in N, N-dimethylformamide (DMF) and dimethyl sulfoxide, respectively. Polymerization proceeds in a “living”/controlled way as evidenced by kinetic studies and chain extension results, producing well-defined polymers with controlled degree of polymerization and narrow molecular weight distribution. The apparent activation energy of polymerization in DMF is accounted to be 36.2 kJ/mol, and the energy of equilibrium state is calculated to be 13.9 kJ/mol. An increase in the concentration of Yb(0) yields a higher monomer conversion. It is observed that polymerization rate experiments a rapid increase in the presence of more polar solvent water, and increasing in the content of H2O results in an increase in the apparent rate constant of polymerization, and a decrease in the molecular weight distribution. The reaction rate and molecular weight increase along with the decrease of DMF content. The effect of Yb(0) powder content, different ligands and concentration of initiator on the polymerization is also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Upconversion luminescence in Tm 3+/Yb 3+co-doped lead tungstate tellurite glasses

This work reports the upconversion luminescence properties of Tm 3+/Yb 3+ ions in lead tungstate tellurite (LTT) glasses. Judd–Oflet intensity parameters have been obtained from the absorption band intensities of Tm 3+ singly-doped and Tm 3+/Yb 3+ co-doped LTT glasses. The spontaneous emission probabilities, radiative lifetimes and branching ratios for 1G 4 and 3H 4 emission levels of Tm 3+ have been determined. Upconversion luminescence has been observed by exciting the samples at 980 nm (Yb 3+: 2F 7/2→ 2F 5/2) at room temperature. Four upconversion emission bands corresponding to the 1G 4→ 3H 6 (477 nm), 1G 4→ 3F 4 (651 nm), 1G 4→ 3H 5 (702 nm) and 3H 4→ 3H 6 (810 nm) transitions have been identified. The relative variation in the intensities of upconversion bands, the different channels responsible for upconversion spectra and the effect of Yb 3+ ions concentration on the upconversion luminescence of Tm 3+ ions have also been discussed.

Thermal lensing study based on the heat transfer of diode-pumped Yb3+:Y2SiO5lasers

Based on the features of diode-pumped Yb 3+ :Y 2 SiO 5 (Yb:YSO) lasers, a thermal model was established. According to the latest reports and measurements on thermal parameters, and further considering the heat transfer on side surface, thermal lensing effect of Yb:YSO was studied for the first time to our knowledge. Under the pump power of 17 W, the maximum temperature (488.4 °C) and the maximum distortion (1.24 μ m) were obtained by solving Poisson equation using finite difference method. Moreover, thermal lens focal length was measured through a plane-plane cavity. All the results demonstrate that the theoretical result will be closer to the reality if we take the heat transfer on side surfaces into account.

Hydrothermal synthesis of BaYF 5:Yb 3+/Er 3+ upconversion luminescence submicrospheres by a surfactant-free aqueous solution route

BaYF 5:Yb 3+/Er 3+ upconversion (UC) luminescence submicrospheres have been synthesized by the hydrothermal synthesis method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), scanning probe microscope (SPM), transmission electron microscope (TEM), laser diffraction particle analyzer (LDPA) and UC emission spectra. The as-prepared highly crystalline BaYF 5:Yb 3+/Er 3+ submicrospheres are of uniform size depending on different reaction temperatures and reaction times. It is found that the usage of fluoride source NaBF 4 plays the crucial key in the formation of submicrosphere. Under the 980 nm excitation, the UC emission transitions for 4F 9/2→ 4I 15/2 (red), 2H 11/2, 4S 3/2→ 4I 15/2 (green) in the BaYF 5:Yb 3+/Er 3+ submicrospheres came from two-, two-, and two-photon UC processes, respectively. Further, the effects of Yb 3+ ion concentration, size and surface of as-prepared submicrospheres, and pumping power on the UC luminescence properties of BaYF 5:Yb 3+/Er 3+ have also been discussed.

Intense blue photoluminescence of the Tm 3+/Yb 3+ co-doped single-crystalline hexagonal phase NaYF 4 nanorods

In this paper, Tm 3+/Yb 3+ co-doped NaYF 4 single-crystalline nanorods were prepared via a rational hydrothermal method using oleic acid as a stabilizing agent. The microstructure analysis revealed that the as-prepared samples presented a pure hexagonal phase NaYF 4 structure with high quality rod-like morphology by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). Under 980 nm excitation, the intense blue and weaker red upconversion emissions of the NaYF 4: 1%Tm 3+/ x%Yb 3+ ( x = 2, 5, 10 and 15) samples centered at 450, 477, 649 and 690 nm were observed, which were attributed to the 1D 2 → 3F 4, 1G 4 → 3H 6, 1G 4 → 3F 4 and 3F 3 → 3H 6 transitions of Tm 3+, respectively. Moreover, the photograph of the 1%Tm 3+/10%Yb 3+ co-doped NaYF 4 nanorods exhibited a strong eye-visible blue emission. The upconversion luminescence mechanisms for the Tm 3+/Yb 3+ co-doped hexagonal phase NaYF 4 nanorods were analyzed. In addition, the effect of Yb 3+ ions concentrations on the photoluminescence properties of the Tm 3+/Yb 3+ co-doped hexagonal phase NaYF 4 nano-rods were investigated in detail.

Effect of Yb^3+ concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silica-based glasses

The effect of Yb(3+) concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silicate glasses is investigated. The optimal Bi(2)O(3) concentration range is about 2.0-2.5 mol% in 65SiO(2)-10Al(2)O(3)-25CaO matrix (SAC glasses). For Yb/Bi codoped SAC glasses, the maximum emission intensity excited by 980 nm LD is ~30 times and 1.5 times higher than that of single Bi-doped SAC glasses excited by 980 nm and 808 nm LD, respectively, the peak emission shows obvious red-shift from 1185 nm to 1235 nm band with the Yb(2)O(3) concentration change from 0 to 3.0 mol%. For the same Yb(2)O(3) concentration in SAC glasses, the measured fluorescence lifetime near 1020 nm of single Yb(3+)-doped glasses is longer than that of Yb/Bi codoping glasses, which implyes the efficient energy transfer from Yb(3+) to Bi(n+) in SAC glasses. The results indicate Yb(2)O(3) can be induced into the bismuth-doped silicate glasses to enhance the emission intensity and control the peak wavelength.

Effect of Yb, Gd, and Nd Substitution at the Sr Site on the Metal–Insulator Transition of the (Bi,Pb)‐2212 System

Resistivity measurements in the temperature range (64–300 K) were used to study the metal–insulator transition (MIT) driven by a change in the carrier concentration of the Bi1.7Pb0.4Sr2Ca1.1Cu2.1Oy [(Bi,Pb)‐2212] system. The carrier‐concentration is changed by substituting rare‐earth (RE) elements (Nd, Gd, and Yb) at the Sr site of (Bi,Pb)‐2212. Results show that at higher levels of RE substitution, MIT occurs in (Bi,Pb)‐2212, during which the resistivity becomes minimum at a particular temperature(Tmin) for a particular doping level. Below this temperature, resistivity increases with a decrease in the temperature and vice versa, showing an insulating and a metallic nature, respectively. This Tmin and the carrier concentration at which MIT occurs depend on the substituted RE.

The effect of Yb3+ concentrations on the properties of Yb,Er:YAl3(BO3)4 crystals

The effect of Yb 3+ concentrations on the properties of Yb 3+ and Er 3+ co-doped YAB crystals has been investigated in this paper. The dependence of the emission intensity on the Yb 3+ concentration has been depicted according to the energy transfer model. The decay curves of 2 F 5/2 level of Yb 3+ ion and 4 I 13/2 level of Er 3+ ion in the different Yb 3+ concentration crystals have been measured. The results show that the lifetime of 2 F 5/2 level of Yb 3+ ion is heavily affected by Yb 3+ concentration, contrary to that of 4 I 13/2 level of Er 3+ in the crystals.

Concentration effect of Yb 3+ on the thermal and optical properties of Er 3+/Yb 3+-codoped ZnF 2–Al 2O 3–P 2O 5 glasses

The effects of Yb 3+ and Er 3+ dopants on the optical and thermal properties and chemical durability of 40ZnF 2–10Al 2O 3–50P 2O 5 glasses (nominal molar composition) have been investigated. The glass transition temperature ( T g), dilatometric softening temperature ( T s), crystallization temperature ( T c), refractive index, density, and durability in water increase with increasing Er 3+ and Yb 3+ contents, whereas the thermal expansion coefficient decreases. Red (645 nm) and near infrared (1.535 μm) emissions are simultaneously observed at room temperature with excitation at 980 nm. The red up-conversion and 1.5 μm emission spectra are associated with the 4F 9/2 → 4I 15/2 and 4F 13/2 → 4I 15/2 transitions of Er 3+, respectively, and the up-conversion excitation processes have been analyzed. The Yb 3+ ions enhance the up-conversion and emission processes. The results suggest that the Er 3+/Yb 3+-codoped ZnF 2–Al 2O 3–P 2O 5 glasses may be a potential material for developing optical amplifiers and up-conversion optical devices.

Effect of Yb 3+ concentration on the structures and upconversion luminescence properties of Y 2O 3:Er 3+ ultrafine phosphors

Y 2O 3:Er 3+ ultrafine phosphors with a varying Yb 3+ ion concentration were prepared by a urea homogeneous precipitation method. The results of XRD show that all the samples are of a pure cubic structure and the average crystallite sizes can be calculated as 45, 34, and 28 nm for Y 2O 3:Er 3+ ultrafine phosphors with Yb 3+ ion concentrations of 0, 10%, and 20%, respectively. The lattice constant and cell volume of the ultrafine phosphors decrease with enhancing Yb 3+ ion concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green and red upconversion emission were observed, and attributed to the 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions of Er 3+, respectively. The intensity of red emission increases with increasing Yb 3+ ion concentration. The effect of Yb 3+ ion concentration on the structures and upconversion luminescence mechanism were discussed.

Effect of the ytterbium concentration on the upconversion luminescence of Yb 3+/Er 3+ co-doped PbO–GeO 2–Ga 2O 3 glasses

The effect of Yb 3+ concentration on the frequency upconversion (UPC) of Er 3+ in PbO–GeO 2–Ga 2O 3 glasses is reported for the first time. Samples were prepared with 0.5 wt% of Er 2O 3 and different concentrations of Yb 2O 3 (1.0–5.0 wt%). The green (523 and 545 nm) and red (657 nm) emissions are observed under 980 nm diode laser excitation. The dependence of the frequency UPC emission intensity upon the excitation power was examined and the UPC mechanisms are discussed. An interesting characteristic of these glasses is the increase of the ratio of red to green emission, through an increase of the Yb 3+ concentration due to an efficient energy transfer from Yb 3+ to Er 3+.

Effects of Yb 3+ on the corrosion resistance and deposition rate of electroless Ni–P deposits

Ni–P alloy coatings were deposited with the addition of Yb 3+ in the electroless plating solution. The effects of Yb 3+ concentration on the corrosion resistance and deposition rate of electroless Ni–P coatings were investigated. The results showed that the addition of Yb 3+ could significantly improve the corrosion resistance of the coatings. When increasing Yb 3+ up to 0.20 g L −1, the corrosion potential E corr of the electroless Ni–P coating in 3.5% NaCl solution increased from −0.381 to −0.08 V, and the corrosion current density I corr decreased from 7.36 to 0.62 μA cm −2. At 0.20 g L −1 Yb 3+, the coating could be as long as 960 h free of corrosion in the neutral salt spray. In addition, the deposition rate can also be accelerated by Yb 3+ addition. The mechanisms of Yb 3+ influencing on the corrosion resistance and deposition rate of electroless Ni–P coatings were discussed.