Investigations on structure and proton diffusion coefficient of rare earth ion (Y3+/Nd3+) and aluminum codoped α-Ni(OH)2

Rare earth ion (Nd3 /Y3 ) and Al3 codoped α-Ni(OH)2 powers were synthesized by chemical coprecipitation method. The structure was analyzed with X-ray diffraction (XRD) and thermal gravity (TG). Cyclic voltammetry (CV) tests were performed to evaluate the proton diffusion coefficients of the samples. The results indicated that codoping of Y-Al and Nd-Al resulted in more water molecules contained within the crystal lattice and accordingly increased the interlayer spacing. In particular, the Y-Al codoped α-Ni(OH)2 showed a turbostratic structure. The calculated diffusion coefficients of the Y-Al codoped α-Ni(OH)2 and Nd-Al codoped α-Ni(OH)2 were 3.5×10-10 cm2/s and 2.8×10-10 cm2/s, respectively.     

Spectral Properties and Upconversion Luminescence of Er^3＋, yb^3＋： BaWO4 Crystal

The optical quality of Er^3＋, yb^3＋： BaWO4 crystal was gown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er^3＋ ion were fitted to beΩ2 =0.3926 x 10^-20 cm^2, Ω4 =0.0721×10^-20 cm^2, Ω6 =0.0028 ×10.20 cm^2. Emission peaks centered at around 523,544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.     

Paramagnetic Anisotropy of CdGd2（WO4） 4-δ Single Crystal

CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.     

Spectral properties and energy transfer of Tm^3＋/Ho^3＋-codoped Ga2O3-Bi2O3-GeO2-PbO glasses

The 2.0 μm emission originating from Ho^3＋：^5I7→^5I8 were investigated upon excitation with 808 nm laser diode （LD） transition in Ho^3＋/Tm^3＋-codoped gallate-bismuth-germanium-lead glasses Energy transfer （ET） process between Tm^3＋： ^3F4 level and Ho^3＋： ^5I7 level was also discussed. It was noted that the measured peak wavelength and stimulated emission cross-section of Ho^3＋-doped bismuth-germanium-lead glasses were -2.02 μm and 5.1×10^-21 cm^2, respectively. Intense emission of Ho^3＋ in Tm^3＋/Ho^3＋-codoped GBPG glass were observed, which resulted from the ET between Tm^3＋： ^3F4 and Ho^3＋： ^5I7 level upon excitation with 808 nm LD.     

Luminescent Properties of Green Phosphor Ca8Mg（SiO4 ）4 Cl2：EU^2＋ , DY^3＋ for LED Applications

The new phosphor calcium magnesium chlorosilicate, codoped with Eu^2＋ and Dy^3＋, was synthesized with the help of the high temperature solid state reaction in reducing atmosphere. The excitation and emission spectra were very similar to that of Ca8Mg（SiO4）4Cl2 ：Eu^2＋, and the Dy^3＋ concentration influenced the emission intensity of this phosphor. The intensity of Eu^2＋ and Dy^3＋ codoped CMSC was stronger than that of Eu^2＋ singly doped CMSC. The emission spectrum of the Dy^3＋ ion overlapped the absorption band of the Eu^2＋ ion, indicating that an energy transfer from Dy^3＋ to Eu^2＋ took place in CMSC：Eu^2＋, Dy^3＋ phosphor. The mechanism of the energy transfer from Dy^3＋ tO Eu^2＋, in this phosphor, might be resonant energy transfer.     

Electrochemical Behavior of Dissolved Fe2O3 in Molten CaCl2-KF

The electrochemical behavior of dissolved Fe2O2 in 82.5CaCl2-17.5KF （mole percent, %） was studied using cy clic voltammetry, chronoamperometry, and galvanostatic electrolysis at 827 ℃, and the deposits were characterized by XRD and SEM. Pure iron was deposited on a rotating cylinder （210 r/min） with a cell voltage less than -- 1.0 V. Deposition rate was controlled by diffusion on a molybdenum electrode. The diffusion coefficient of iron species Fe（ Ⅲ ） in the melt at 827 ℃ was found to be 9.7×10^-5 cm^2/s.     

Investigation of Modification Effect of B2O3 Component on Optical Spectroscopy of Er^3＋ Doped Tellurite Glasses

To investigate the modification effect of the B2O3 component on tellurite glass, a series of glasses with a composition of xB2O3-（80-x）TeO2-10ZnO-10Na20 （x = 0, 10, 20, 30, 40, 50, 60, 70, 80） and an additional amount of 0.5% Er2Os（in molar） were prepared. The refractive index, the absorption edge of the host, the J-O parameters of Er^3＋ , the fluorescent decay time, the bandwidth, and the quantum efficiency for the 4Ⅰ13/2→4Ⅰ15/2 transition were obtained theoretically and experimentally. These results indicated that the introduction of B2O3 modified the performance of the tellurite glass. For example, with increasing content of B2O3, the refractive index of the host decreases from 1.9 to 1.5, the absorption edge of the host shifted toward the blue regime, the intensity parameter Ω6 changed from 1.08 × 10^-20（for the pure tellurite glass） to 1.98 ×10^-20 cm^2（for the pure borate glass）, the bandwidth of the 4Ⅰ13/2→4Ⅰ15/2 transition increased, and the quantum efficiency of the 4Ⅰ13/2→4Ⅰ15/2 transition decreased.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Synergistic extraction of rare earth by mixtures of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester and di-（2-ethylhexyl） phosphoric acid from sulfuric acid medium

The extraction of Nd^3＋ and Sm^3＋, including the extraction and stripping capability as well as the separation effect of Nd^3＋ or Sm^3＋, from a sulfuric acid medium, by mixtures of di-（2-ethylhexyl） phosphoric acid （HDEHP, H2A2（0）） and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester （HEH/EHP, H2L2（0）） were studied. The distribution ratios and synergistic coefficients of Nd^3＋ and Sm^3＋ in different acidities were also determined. A synergistic extractive effect was found when HDEHP and HEH/EHP were used as mixed extractants for Sm^3＋ or Nd^3＋. The chemical compositions of the extracted complex were determined as Nd.（HA2）2-HL2 and Sm.（HA2）2-HL2. The extraction equilibrium constants, enthalpy change, and entropy change of the extraction reaction were also determined.     

Energy transfer and frequency upconversion in Er~（3＋）-Yb~（3＋） codoped oxy-fluoro-tungstosilicate glasses

Er3+-Yb3+ codoped oxy-fluoro-tungstosilicate glasses with infrared-to-visible frequency upconversion luminescence were prepared by melting quenching in air.The effects of Er3+ doping on the optical properties of the samples were measured by means of techniques such as optical absorption spectra and photoluminescence spectra.The results showed that intense green and red signals centered at 546 and 665 nm,corresponding to the 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ by a multiphoton stepwise phonon-assisted excited-state absorption process,respectively,were simultaneously observed by exciting the samples with a diode laser operating at 980 nm at room temperature.The upconversion process was found very sensitive to Er3+ content at a constant Yb2O3 content of 5 mol.%.With the increase of Er3+ content from 0.5% to 1.5%,the upconversion intensity increased gradually.Further increasing of Er3+ content to 3.0% resulted in a significant fluorescence quenching.Moreover,the possible upconversion mechanisms were discussed based on the energy-matching conditions and the quadratic dependence on excitation power.     

Investigation on pumping oxygen characteristics of （Bi2O3）0.73（Y2O3）0.27 solid electrolyte

（Bi2O3）0.73（Y2O3）0.27 fine powders prepared by wet chemical precipitation method were cold isostatically pressed to form solid electrolyte tubes, and sintered at 900 ℃ for 10 h in the air. Their pumping oxygen characteristics in non-dehydrated Ar gas were investigated, where a ZrO2 （Y2O3 stabilized） oxygen sensor was used to measure the oxygen partial pressure Po2. The results showed that the Po2 value reached magnitudes of 1×10^-2-1×10^-10 Pa at the applied pumping oxygen voltage of 0.5 V, 1×10^-37-1×10^-27 Pa at 1.0 V and 1×10^-53-1×10^47 Pa at 2.0 V within the temperature range from 550 to 650 ℃. Moreover, no cracks were found in the tested solid electrolyte tubes. Thus, the Bi2O3-Y2O3 system might be used in solid electrolyte oxygen pump for purifying gases.     

Synthesis of colloidal LaF3： 0.04Yb^3＋, 0.01Er^3＋ nanocrystals with green upconversion luminescence

A synthesis of LaF3：0.04Yb^3＋,0.01Er^3＋ nanocrystals with oleic acid as a capping ligand was presemed. The X-Ray Diffraction （XRD） pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy （TEM） demonstrated that the average size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb^3＋-Er^3＋ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrystals were potentially applicable in biolabeling and bioimaging.     

Growth and characterization of new laser crystal Nda3＋：ca2.85Gd0.1（VO4）2

The crystal growth, crystal defect, thermal properties and luminescence properties of Nd3+:Ca2.85Gd0.1(VO4)2 were investigated. Nd3+:Ca2.85Gd0.1(VO4)2 crystal grown by Czochraski method was green colored, and was not transparent, which was possibly due to residual impurities in V2O5, or due to the lack of oxygen in the growth process. And the Nd3+:Ca2.85Gd0.1(VO4)2 crystal had the existence of 180° do-mains. However, the annealing method could effectively decrease the crystal defect and greatly improve the quality of crystal. The average thermal expansion coefficients calculated were α⊥c=9.5767×10-6 K-1, α∥c=10.7647×10-6 K-1, respectively. The specific heat of Ca2.85Gd0.1(VO4)2 was 0.401 J/(g·K) at 330 K. The polarized absorption spectra and the polarized fluorescence spectra of Ca2.85Gd0.1(VO4)2 were measured at 330 K. Based on the Judd-Ofelt theory, the intensity parameter Ωλ (λ=2, 4, and 6), the radiation transition probabilities τrad, the stimulated-emission cross section σp in Nd3+:Ca2.85Gd0.1(VO4)2 crystal were calculated.     

Luminescence properties of YAl3（BO3）4 phosphors doped with Eu^3＋ ions

YAl3 （BO3）4： Eu^3＋ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction （XRD） and scanning electron microscope （SEM）. Doping YAl3（BO3）4： Eu^3＋ phosphors with concentration of Eu^3＋ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3（BO3）4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength region. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu^3＋ ions in YAl3（BO3）4： Eu^3＋ phosphors was 8 mol%.     

Study on the preparation and electrochemical performance of rare earth doped nano-Ni（OH）2

Multiphase nano-Ni(OH)2 doped with Y or La was prepared by supersonic co-precipitation method. The crystal morphology, structure and particle size were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and particle size distribution (PSD). The electrochemical performance of samples was investigated by electrochemical workstation and battery tested system. The results indicated that micro-morphology and grain size were changed with the changing of supersonic power, pH values and doping elements. The morphology of Y doped sample was from the flake-like to the needle-like with the increase of supersonic power; Particles were from quasi-spherical particles into needle-like with the increase of pH values; As the supersonic power increased, the proportion of α-Ni(OH)2 increased initially and then decreased. pH value was very important to the formation of crystalline phase. Lower pH value was beneficial to the formation of α-Ni(OH)2. However, the pH values had a slight effect on the reaction reversibility. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacity of electrodes increased initially and then decreased with the increase of supersonic power. When the supersonic power was 60 W and the pH value was 9, the sample had the largest dis-charge capacity (358 mAh/g) at 0.5 C rate, which was 122.7 and 76 mAh/g higher than the spherical nickel electrode and La doped sample electrode, respectively.     

Investigation on energy transfer from Er^3＋ to Nd^3＋ in tellurite glass

A study of energy transfer of Er^3＋/Nd^3＋ codoped tellurite glasses was presented. By Nd^3＋ co-doping, both the Er^3＋ green emission corresponding to the Er^3＋： （^4S3/2, ^2H11/2）→^4I15/2 transitions and the red emission corresponding to the Er^3＋： ^4F9/2→^4I15/2 transitions were quenched. The energy transfer mechanism between Er^3＋ and Nd^3＋ was discussed based on their energy level characteristics. The interaction parameters, CO-A, for the energy transfer processes from Er^3＋ to Nd^3＋ in tellurites glass were calculated. Finally, the resonant transfer Er^3＋： ^4I9/2→Nd^3＋： （^4F5/2, ^2H9/2） was proposed to be the most probable microscopic process to occur in contrast with the other processes.     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Electroanalytical tools to investigate the divalent state of Eu（III） and Nd（III） ions in non-aqueous medium

The divalent state of Ln(Ⅲ) ions has attracted much interest because of their ability to serve isomorphously in many biological sys-tem of divalent Ca(II) ion. Therefore, present paper deals with the study of divalent state of Eu(Ⅲ) and Nd(Ⅲ) ions in non-aqueous medium. In present study, cyclic voltammetry and chronopotentiometry were utilized to establish the divalent state of Eu(Ⅲ) and Nd(Ⅲ) ions. The cy-clic voltammetric technique showed two-step reduction process at cathode for both Ln(Ⅲ) ions under specified experimental conditions and chronopotentiometric method also showed two different transition times (). Looking to the shape of cyclic voltammogram we calculated het-erogeneous forward rate constant (K0fh, cm/s) and diffusion coefficient (D, cm2/s) for both ions, which suggested that sweep rate had great ef-fect on the shape of cyclic voltammogram of Eu(Ⅲ) and Nd(Ⅲ) ions. The result of chronopotentiometry also suggested that stable divalent states of Eu(Ⅲ) and Nd(III) ions existed with chronopotentiogram with two distinct transition times. The diffusion coefficients (D, cm2/s) were calculated from Sand equation. The diffusion coefficients of both techniques were compared and the results suggested that the system at electrode surface was changing from being reversible to irreversible.     

Sol-gel processed Ce^3＋, Tb^3＋ codoped white emitting phosphors in Sr2Al2SiO7

Sr2Al2SiO7：Ce^3＋, Tb^3＋ white emitting phosphors were fabricated using the sol-gel method. X-Ray Powder Diffraction （XRD） analysis confirmed the formation of Sr2Al2SiO7：Ce^3＋, Tb^3＋. Scanning Electron Microscopy （SEM） observation indicated that the microstructure of the phosphor consisted of regular fine grains with an average size of about 0.5-1 μm. Luminescence properties were analyzed by measuring the photoluminescence spectra. The Ce^3＋, Tb^3＋-codoped Sr2Al2SiO7 phosphors showed four main emission peaks： one at 414 nm for Ce^3＋ and three at 482, 543, and 588 nm for Tb^3＋. The emission spectra of the samples with different doping concentrations showed that the Tb^3＋ emission was dominant because of the persistent energy transfer from Ce^3＋. The decay characteristic was better than that prepared by the solid-state process in the comparable condition. The codoped phosphor displayed long persistent white phosphorescence.     

Luminescent properties and energy transfer of color-tunable Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors

Phosphors with controlled emission spectra are of great interest due to their application for white light emitting diodes.Herein, a new class of Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors were synthesized by a facile sol-gel combustion method. The phase structure,morphology, and luminescence properties of the phosphors were characterized by using powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and photoluminescence excitation and emission spectra,respectively. The results on luminescence properties indicated that co-doped Ce3＋ ions served as UV-light sensitizers with excitation energy partially transferred to Tb3＋ ions, leading to green emission from Tb3＋. Particularly, the corresponding emitting colors of the phosphors could be well-tuned from deep blue（0.16, 0.05） to green region（0.25, 0.45） by adjusting the molar ratio of Ce3＋/Tb3＋.