Investigation on Structures and Properties of Yb3＋-Doped Laser Glasses

The Yb3^＋ -doped silicate, phosphate and borophosphate laser glasses were prepared by means of conventional melt quenching technology. The physical and spectral properties of the glasses were investigated. The results show that, due to the existence of OH^-, the fluorescence lifetime of phosphate glass is shorter than that of silicate glass, so silicate glass has better spectral properties than phosphate glass. Silicate glass has better mechanical and thermal properties than phosphate glass, but with the addition of B2O3, mechanical and thermal properties of phosphate glass are improved greatly without fluorescence quenching effect. This kind of borophosphate glass can be used in high average power solid state lasers.     

Preparation of La（OH）3 and La2O3 with Rod Morphology by Simple Hydration of La2O3

Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of the hexagonal phase of La（OH）3, indicating that the hydration process is very rapid. The as-prepared La（OH）3 is almost entirely with a needle- or rod-like shape with a width of 2 - 3 μm and a length of 5 - 8 μm. The mechanism of the formation of La（OH）3 with rod-like morphology was preliminarily presented. It is easier to expand the simple hydration process on a large scale than the hydrothermal process.     

Experimental Study and Thermodynamical Calculation on the Formation of Eutectic Phase of MnS-RE_2S_3 and(Mn,Ca)S-RE_2S_3 in Sulfur-Containing Free-Cutting Steel

The free-cutting phase in RE or Ca-RE treated sulfur-containing free-cutting steel is the eutectic phasesof MnS-RE_2S_3 and (Mn,Ca)S-RE_2S_3,respectively.The atomic ratio of RE/S needed to modify all theMnS into the eutectic phase is higher than 1.48 or 1.41-1.37 Ca/S,when RE or Ca-RE is used as the modifiz-er in the sulfur-containing free-cutting steel.Moreover,the thermodynamical calculation shows that theeutectic temperature is lower than the solidifying temperature,which is the key condition for the eutectic phase tokeep globual during solidifying.     

Function of Oxygen in Mo-La2O3 Cathode

Different atomic ratio La/O film cathodes were prepared by pulsed laser deposition under various vacuum conditions. The emission properties were measured and their surface composition was investigated with in situ AES analyses. The function of oxygen in thermoionic emission of Mo-La2O3 cathode was investigated. Excess oxygen is negative to electron emission because lanthanum is easy to become stable La2O3, but proper proportion oxygen can weaken the evaporation of lanthanum and conduce to cathodes＇ stable work. The formation of oxygen vacancies enhances semiconductor property of La-O compound and improves greatly the performance of cathodes.     

Study on Addition of Yttrium to Heat-Resistant Materials by Laser Surface Melting

Addition of rare earth(RE)such as Y in the surface layer of gray cast iron or Ni-based superalloy by lasersutface melting was carried out using a 2 k W CO_2 laser.For delivering the element Y to the metal surface dur-ing laser irradiation,several methods were employed.It is found that Y-containing surface modified layer can hecontrollably obtained on substrates,a gray cast iron can be laser surface-modified with Cr+Al-Y powder re-sulting in a thin layer of Fe-Cr-Al-Y alloy such as 30Fe40Cr27Al3Y.     

Laser induced broadband white emission of Y2Si2O7 nanocrystals

The generation of broadband white emission of the α-Y_2Si_2O_7 nanocrystals was observed upon excitation by focused beam ofCW lasers operating in near infrared,visible and blue regions.The influence of excitation energy on order of process is presented.The temperature of sample emitting laser induced white emission(LIWE) was determined by luminescence nanothermometry technique.It is found that the temperature is much lower than that predicted by blackbody model characterized with the same energy.It is shown that the LIWE is accompanied by efficient photocurrent.An origin of white emission is discussed in terms of multiphoton ionization process leading to the inter valence charge transfer emission.     

Effects of Support on Catalytic Behavior of Combustion Catalyst La0.8Sr0. 2CoO3／γ-Al2O3

Combustion catalyst La0.8Sr0.2CoO3 (LSC) is expected to possess relatively high activity for the oxidation of carbon monoxide and many hydrocarbons. If γ-Al2O3 is used as its support, cobalt ions can easily react with γ-Al2O3 at not very high temperature to form spinel CoAl2O4 or spinel-like, which decreases the activity of the combustion catalyst. In this paper, MgAl2O4 and CaAl2O4 were pre-eoated on γ-Al2O3 by impregnation respectively, which formed compound support for LSC. It is shown that, when MgAl2O4 layer is covered on the surface of MgAl2O4 by impregnation, the entering of cobalt ions into γ-Al2O3 lattice is restrained, then LSC formed on the surface of MgAl2O4, which leads to a good catalytic activity of xylene complete oxidation. But the layer of MgAl2O4 should be thick enough to reach 30% (mass fraction) MgO in the support due to large size particle of MgAl2O4 crystalline. If polyvinyl alcohol (PVA) is added into the impregnation solution adequately, MgAl2O4 particles formed on the surface of γ-Al2O3 are getting smaller, and less amount of MgAl2O4 is needed to cover up the surface of γ-Al2O3. If CaAl2O4 layer substituted for MgAl2O4, more closed cover is obtained in virtue of fine particles of CaAl2O4. The activity examination shows that smaller particles of MgAl2O4 or CaAl2O4 Call be more effective to hinder cobalt ions entering the lattice of γ-Al2O3, and better activities will be obtained.     

Effect of AI2O3 on Structure and Wearability of Composite Coating

The composite coating was prepared by thermal spray welding after making composite powder, which is composed of Ni based self melted alloy and AI2O3 ceramic powder including nano, sub-micron and micron powders. The influences of contents and sizes of AI2O3 on the structure and wearability were investigated. The results show that the wear resistance of the coating would be increased greatly by adding AI2O3, but the spray weldability decreases with increasing AI2O3 content. So there is an optimal content of AI2O3 powder. The composite coating with AI2O3 nano or sub micron powder of 0.5% has the best abrasive resistance, while the optimal content of AI2O3a micron powder is 1%.     

Effects of La and Nd on the Fermentation of Alginic Acid Produced from the Strain 342 of Azotobacter Vinelandii

It is reported that fermentative liquids with various concentrations of La and Nd affect the fer-mentation of alginic acid from the strain 342 of Azotobacter vinelandii.The results are as follows:When theconcentration of La or Nd was up to 100 ppm,the cell growth is stimulated and the production of alginic acidis promoted.The La or Nd in concentration higher than 200 ppm or 150 ppm inhibits the fermentation,respectively.As the concentration range of La is 0～100 ppm or that of Nd is 0～150 ppm,the yield of fixednitrogen increases,and the ratio of c_M to c_G(c_M/c_G)decreases with the raise of the concentration of La orNd.When the concentration range of La is 100～400 ppm and that of Nd is 150～400 ppm,the conclusion iscontrary to the above mentioned result.     

Infrared Laser Pumped Green and Blue Laser Emissions from a Single Solid State Material Doped by Rare Earth ions

The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared laser pumped rare earth doped nonlinear laser crystals by means of self-frequency-conversion and from infrared laser pumped rare earth-doped bulk, fiber and microsphere materials by means of frequency upconversion are introduced in detail. Other kinds of devices and methods are also compared. The typical nonlinear laser crystals such as YA13(BO3)4, GdA13(BO3)4, YCa4O(BO3)3,GdCa4O(BO3)3, and the typical upconversion fluoride fibers are compared and analyzed. The major problems remaining to be solved and the developing trends in the area are also discussed.     

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.     

Green,orange, and red upconversion luminescence in Nd^3＋/Yb^3＋： Cs2NaGdCl6 powders under 785 nm laser excitation

Nd^3＋：Cs2NaGdCl6 and Nd^3＋, Yb^3＋：Cs2NaGdCl6 polycrystalline powder samples were prepared by Morss method E. Under 785 nm semiconductor laser pumping, the upconversion luminescence of Nd^3＋ ions in Cs2NaGdCl6 was investigated at room temperature, and three upconversion emissions near 538 nm （Green）, 603 nm （Orange）, and 675 nm （Red） were observed and assigned to ^4G7/2→^4I9/2, （^4G7/2→^4I11/2; ^4G5/2→^4I9/2）, and （^4G7/2→^4I13/2; ^4G5/2→^4I11/2 ）, respectively. The dependences of these upconverted emissions on laser power and Nd^3＋ ion concentration were investigated, to explore the upconversion mechanism. The effect of doping Yb^3＋ ions on the upconversion luminescence of Nd^3＋ in Cs2NaGdCl6 was also studied under 785 nm laser excitation. The energy transfer processes were discussed as the possible mechanism for the above upconversion emissions.     

Evidences for non-equivalent centers in mixed chain nickelates （NdxY1-x）2BaNiO5

Absorption spectra of the mixed chain nickelates (Nd_xY_1−x)₂BaNiO₅ were measured for different x. Experimentally two evidences for the presence of non-equivalent rare-earth centers (NEREC) were found. First, the linewidths show a very strong broadening for x when the calculated distribution over NEREC is wide. Second, a complicated lineshape of the lowest-frequency line in the region of the ⁴I_9/2→⁴I_11/2 electronic transition is in good agreement with statistics of NEREC. A simple modeling for the line broadening due to NEREC is suggested.     

Characterization of Y2O2S： Eu^3＋, Mg^2＋, Ti^4＋ Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y₂O₂S: Eu³⁺, Mg²⁺, Ti⁴⁺ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu₂O₃ content in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y₂O₂S: Eu³⁺ crystal structure, Eu³⁺ ions only replaced Y³⁺ ions' places in which it posited center position of c axis. With the increase of Eu₂O₃ content, the position of the strongest emission peak changed from 540 nm (⁵D₁→⁷F₂ transition) to 626 nm (⁵D₀→⁷F₂ transition), and the maximum intensity was obtained when x = 0.09 in Y₂O₂S: Eu_x³⁺ (0.01 ≤ x ≤ 0.10). This is due to the environment of trivalent europium in the crystal structure of Y₂O₂S. Doping with Mg²⁺ or Ti⁴⁺ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg²⁺ and Ti⁴⁺ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd · m⁻²). Thus the LLP mechanism was analyzed.     

Infrared to ultraviolet upconversion luminescence in Nd doped nano-glass-ceramic

Nd^3＋ doped transparent oxyfiuoride glass ceramic containing β-YF3 nanocrystals was prepared and the upconversion luminescence behaviors of Nd^3＋ in the precursor glass and glass ceramic were investigated. Under 796 nm laser excitation, ultraviolet upconversion emissions of Nd^3＋ ions at 354 nm （^4D3/2→^4I11/2） and 382 nm （^4D3/2→^4I11/2） were observed at room temperature. Power dependence analysis demonstrated that three-photon upconversion processes populated the ^4D3/2 excited state. In comparison with those of the precursor glass, the ultraviolet emissions were enhanced by a factor of 500 in the glass ceramic, which was attributed to the change in the ligand field of Nd^3＋ ions and the decrease in phonon energy because of the partition of Nd^3＋ ions into the β-YF3 nanocrystals after crystallization.     

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.     

Effect of Metal Oxide Doping into Ce0.5Zr0.5O2 on Catalytic Activity of MnOx/γ-Al2O3/Ce0.45Zro.45M0.1Ox （M = Y, La, Mn） Honeycomb Catalysts

This article showed that the catalytic activity of MnOx/γ-Al2O3/Ce0.5Zr0.5O2 monolithic catalyst toward the catalytic combustion of ethanol in a fixed bed reactor could be greatly improved by doping three metal oxides into Ce0.5Zr0.5O2. The catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45M0.1 Ox （M = Y, La, Mn） is better than that of MnOx/γ-Al2O3/Ce0.5 Zr0.5O2. The order of activity of the catalysts is as follows： MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1Ox 〉 MnOc/γ-Al2O3/Ce0.45 Zr0.45La0.1Ox 〉 MnOx/γT-Al2O3/Ce0.45Zr0.45Mn0.1Ox 〉 MnOx/y-Al2O3/Ce0.5Zr0.5O2. The influence of the loading amount of manganese oxide in enhancing the catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1 Ox was investigated. The results showed that when MnO2 loading amount was 10% （mass fraction）, the MnOx/Al2O3/Ce0.45Zr0.45Y0.1Ox catalyst recorded the highest activity.     

Luminescent properties of amorphous phosphor 1.4YeO3·2.5Al2O3·0.1Tb2O3 prepared by sol-gel method

Amorphous phosphor 1.4YeO3·2.5Al2O3·0.1Tb2O3 （the same composition as Y2.8Tb0.2Al5O12） was prepared via a sol-gel method at relatively low temperature （i.e., below 650℃）, which is much lower than that for the preparation of polycrystalline Y3Al5O12：Tb^3＋ （above 1400℃）. The amorphous phosphor prepared in the optimized conditions showed a bright green-yellowish luminescence, the intensity of which was comparable with that of polycrystalline sample and the emissions of which were assigned to 5D4 → 7Fj transitions of Tb^3＋. Besides the emissions of Tb^3＋, the amorphous samples prepared at temperatures below 500 ℃ presented a weak blue emission band around 420 nm.     

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.     

Synthesis and Spectral Properties of Nd^3＋： Gd3Ga5O12 Nanopowder for Transparent Laser Ceramics

Nd^3＋： Gd3Ga5O12（Nd ： GGG） nanopowder for transparent laser ceramics was synthesized using sol-gel method. XRD, SEM, and fluorescence spectrum were used to study the properties of Nd^3＋ ：Gd3Ga5O12 nanopowder. XRD patterns of samples show that it has a cubic structure. Meanwhile, pure Nd：GGG crystals were obtained at 1000 ℃ for 12 h. SEM photographs show that dispersed, uniform, ball-like Nd：GGG nanopowder is obtained. Both XRD and SEM results show that the crystallization degree and the grain size increase with the increase in calcining temperature. Analysis of fluorescence spectrum shows that fluorescence emission occurs at 1062.7 nm, which is the result of Nd^3＋ （^4F3/2→^4I11/2） transition. Homogenous Nd ： GGG nanopewder with a small grain size synthesized using the sol-gel method is favorable for sintering the transparent ceramic, which proves that the nanopewder obtained is suitable as a precursor for preparing GGG transparent ceramics.