Study on Lattice Parameter Variance and Eutectic Reaction during Crystal Growth of Nd,Cr∶GSGG by Czochralksi Method

During the crystal growth of Nd, Cr∶GSGG by Czochralski method, in some cases eutectic reaction occurred in the nether region of the crystal, and the boule was divided into two obvious different parts, which is upper Nd,Cr∶GSGG crystal and the nether coexisting Nd,Cr∶GSGG and GdScO3. By X-ray powder diffraction, the structure change of NdCr∶GSGG crystal of Φ 27 mm×120 mm with eutectic along its grown direction <111> was studied. By the least square method and extrapolation function f=sinθ-sinθ1-t(t is an adjustable parameter), the lattice parameters of Nd,Cr∶GSGG and additional GdScO3 phase were computed. The results indicate that the lattice parameters of Nd,Cr∶GSGG increase along its growth direction, which changes from a=(1.25650±0.00007) nm of the top to (1.25798±0.00010) nm of the bottom. In the process of Nd,Cr∶GSGG growth, Gd3 in Nd,Cr∶GSGG is partly replaced by Nd3 with larger ionic radii, and the volatilization of Ga component results in its composition variance, which cause the lattice parameters increase along growth direction. In the eutectic section, there are the Nd,Cr∶GSGG and the second phase orthorhombic GdScO3. The lattice parameters of GdScO3 are a=0.5443±0.0007, b=0.5699±0.0005 and c=(0.7865±0.0009) nm, and that of Nd,Cr∶GSGG is (1.25798±0.00010) nm. In the final growth stage, excessive volatilization of Ga composition during the crystal growth causes the growth melt deflect of the Nd,Cr∶GSGG solid solution range seriously, and results in the eutectic reaction, and the outgrowth of Nd,Cr∶GSGG and GdScO3. So it is necessary to decrease the effect of gallium volatilization during the growth in order to avoid eutectic growth and obtain a high-quality Nd,Cr∶GSGG.     

Improved corrosion resistance and thermal stability of sintered Nd-Fe-B magnets with holmium substitution

The effects of Ho substitution for Nd on the microstructure, corrosion resistance and thermal stability of the Nd-Fe-B magnets were investigated. The(Nd,Ho)-O phase was formed with increasing Ho substitution. The results of potentiodynamic polarization and highly accelerated stress test show improved corrosion resistance with increasing Ho substitution. The optimum mass loss 0.29 mg/cm~2 is achieved.Moreover, the average temperature coefficients for remanence and coercivity in the range of 25-150℃are both closer to zero, indicating improved thermal stability. The mechanisms for the improved corrosion resistance and thermal stability are discussed in relation to the microstructure featuring the(Nd,Ho)-O phase.     

Spin-Dependent Electroresistance Behaviour of Nd0.67Sr0.33MnO3-δ(0≤δ≤0.20)

Oxygen deficient Nd0.67Sr0.33MnO3-δ ceramic samples were prepared using conventional ceramic technology. A colossal electroresistance (CER) effect was found in Nd0.67Sr0.33MnO3-δ series. The electrical transport is magnetically coupled and spin-dependent over grain or phase boundaries. Electrical-field-induced changes of the spin array orientations inside of and between the magnetic domains by grain or phase boundaries have to be concluded for the strong electroresistive effect in Nd0.67Sr0.33MnO3-δ series.     

Application of Stereology on Neodymium-Doped Yttrium Aluminum Garnet （Nd： YAG） Transparent Ceramics

Nd ： YAG precursor powders were synthesized by homogeneous precipitation, and Nd ： YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance and field emission gun-environment scanning microscope. Using statistics and stereology theory, study was carried out on the quantitative relationships between light transmittance and stereological parameters in three-dimensional Euclidean space. It is found that the transmittance of Nd：YAG with 1 mm in thickness is about 45% and 58% in visible and near-infrared wavelength, respectively. The transmittance linearly increases with increasing equivalent sphere diameter and reaches the theoretical value of single crystal when the equivalent sphere diameter is 20μm. The transmittance decreases with the increasing of mean specific area per unit volume of grain and discrete grains, and the transmittance decreases with increasing mean free distance of grains in Nd：YAG ceramics.     

Influences of Nd~（3＋） doping on structure and electrochemical performance of layered Li_（1.05）V_3O_8

Nd3+-doped Li1.05V3O8 was synthesized by liquid-state reactions combined calcination.The influences of Nd3+ doping on physical and electrochemical performances of Li1.05V3O8 were investigated using X-ray diffraction (XRD),cyclic voltammograms,a.c.impedance and galvanostatic charge-discharge tests,etc.Results indicated that Nd3+-doped products had well developed crystal structure of layered LiV3O8 and uniform particle size distribution.Nd3+ doping with a proper amount improved the initial discharge capacity,discharge voltage and ion conductivity of the cathode material to some extent.Nd3+ did not participate in the electrochemical reactions and was beneficial to stability of the crystal structure during cycling.     

Effect of Cobalt on HDDR Anisotropic NdFeB

The effect of cobalt on the magnetic properties and anisotropy of HDDR anisotropic NdFeB was studied.It is found that Co is helpful for preparing anisotropic NdFeB with high coercivity. The research on the initial microstructure for NdFeB alloy indicates that Co tends to enter the crystal lattice of Nd-rich phase and some of Co atoms also enter the crystal lattice of Nd2Fe14B. The dissolution of Co changes the stability of Nd-rich phase and Nd2Fe14 B in H2 atmosphere and affects the kinetics of HDDR phase transformation. As a result, the NdFeB powder exhibits a high coercive force and a strong anisotropy.     

Electrochemical hydrogen storage performances of the nanocrystalline and amorphous（Mg24 Ni10 Cu2）100-x Ndx（x=0–20） alloys applied to Ni-MH battery

Melt spinning technology was used to prepare the Mg2 Ni-type（Mg24 Ni10 Cu2）100–x Ndx（x=0,5,10,15,20） alloys in order to obtain a nanocrystalline and amorphous structure.The effects of Nd content and spinning rate on the structures and electrochemical hydrogen storage performances of the alloys were investigated.The structure characterizations of X-ray diffraction（XRD）,transmission electron microscopy（TEM） and scanning electron microscopy（SEM） linked with energy dispersive spectroscopy（EDS） revealed that the as-spun Nd-free alloy displayed an entire nanocrystalline structure,whereas the as-spun Nd-added alloys held a nanocrystalline and amorphous structure and the degree of amorphization visibly increased with the rising of Nd content and spinning rate,suggesting that the addition of Nd facilitated the glass forming of the Mg2 Ni-type alloy.The electrochemical measurements indicated that the addition of Nd and melt spinning improved the electrochemical hydrogen storage performances of the alloys significantly.The discharge capacities of the as-cast and spun alloys exhibited maximum values when Nd content was x=10,which were 86.4,200.5,266.3,402.5 and 452.8 mAh/g corresponding to the spinning rate of 0（As-cast was defined as the spinning rate of 0 m/s）,10,20,30 and 40 m/s,respectively.The cycle stability（S20,the capacity maintain rate at 20thcycle） of the as-cast alloy always rose with the increasing of Nd content,and those of the as-spun alloys exhibited the maximum values for Nd content x=10,which were 77.9%,83.4% 89.2% and 89.7%,corresponding to the spinning rate of 10,20,30 and 40 m/s,respectively.     

Preparation of Neodymium-Doped Yttrium Aluminum Garnet Transparent Ceramics by Homogeneous Precipitation Method

Neodymium-doped yttriumaluminumgarnet(Nd∶YAG)transparent polycrystalline ceramics,laser ce-ramic matrix materials,are gradually becomingsubsti-tutes for single crystals because they are provided withpredominantly chemical stability,highly doped ionconcentration,excellent optical performance and hightemperature stability[1,2].Presently,the conventionallyused methods to produce Nd∶YAG powders are solid-state processes[3],chemical precipitation methods[4,5]andlowtemperature combustiontechniqu…     

Effect of Rare Earths on Mechanical Properties and Microstructures of Si3N4-based Ceramics

Si3N4-hased ceramics exhibit excellentproperties such as high strength, high corro..sion resistance, high fire resisting property andhigh thermal shock resistance. However, up tonow, the application of St3N4-based ceramicsis still limited by their poor ductility, lowtoughness and stability. Adding fiber or whisher into ceramic matrix is a useful tougheningmethod, but fiber and whisker are costly and itis difficult to homogenize them in ceramic matrix. Furthermore, ceramic powders can not fill…     

Research on poly（styrene-acrylic acid）-supported neodymium complex in catalytic copolymerization of styrene and 4-vinylpyridine

The catalytic activity of poly（styrene-acrylic acid） （PSAA） supported neodymium chloride （NdCl3） complex for the copolymerization of styrene and 4-Vinylpyridine was studied. The influence of various factors, such as Al/Nd molar ratio, reaction time, macromolecular carder （PSAA）, and ratio of styrene to 4-vinypyridine （g/g）, on the copolymerization yield of styrene and 4-Vinylpyridine was investigated. The results showed that the copolymerization of polar monomers with olefins occurred efficiently and the catalytic activity of polymer-supported catalyst was higher than that of the similar small molecular catalysts. The activity of PSAA.Nd complex increased with in- creasing Al/Nd molar ratios and decreased with increasing polymerization time. The highest activity of PSAA＇Nd was observed at 120 min, and the highest yield was found at the ratio of styrene to 4-vinylpyridine of 4：2. DSC analysis presented that the resulted polymer had only one glass transition temperature, and showed very good thermal stability.     

Influence of oxygen non-stoichiometry on physical properties of NdSr2Mn2O7±δ

Nd Sr2Mn2O7+δ compounds were synthesized by ceramic method under three different cooling conditions. The Nd Sr2Mn2O7+δ samples were characterized by powder X-ray diffraction(XRD). Oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy(XPS) methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. Magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies(OV) and strong competition between the superexchange and double exchange interactions.     

Crystal Growth and Laser Characteristics of Nd~(3+)∶KGd(WO_4)_2

The solid-state diode-pumped laser was widelyusedin many fields.With the development of crystalgrowth,many good working materials were discov-ered,such as:Nd3+∶YAG,YVO4[1],YLF[2,3],andNd3+∶KY(WO4)2(Nd∶KYW),Yb3+∶KY(WO4)2(Yb∶KYW),Nd3+∶KGd(WO4)2(Nd∶KGW)in recent10years.Compared with Nd∶YAG,Nd∶KGWhas manyoutstanding properties:the emission cross section isbig at the output wavelength of1064and1351nm,concentrate quenching of high Nd3+(at a maxi mumof10%)(atomfraction)is v…     

Chemical stability and electrical property of Ba_(1.03)Ce_(0.6)Zr_(0.2)Yb_(0.2)O_(3-α) ceramic

Ba1.03Ce0.6Zr0.2Yb0.2O3-α ceramic was prepared by solid state reaction. Phase composition, surface and cross-section morphologies of the material were characterized by using X-ray diffractometer (XRD) and scanning electron microscopy (SEM), respectively. Its chemical stability against carbon dioxide and water steam at high temperature was tested. Ionic conduction of the material was investigated by ac im-pedance spectroscopy and gas concentration cell methods under different gas atmospheres in the temperature range of 500-900 ℃. Using the ceramic as solid electrolyte and porous platinum as electrodes, the hydrogen-air fuel cell was constructed, and the cell performance at the tem-perature from 500 to 900 oC was examined. The results indicated that Ba1.03Ce0.6Zr0.2Yb0.2O3-α was a single-phase perovskite-type ortho-rhombic system, with high density and good chemical stability under carbon dioxide and water steam atmospheres at high temperature. In wet hydrogen, the material was a pure protonic conductor with the protonic transport number of 1 from 500 to 700 ℃, a mixed conductor of pro-ton and electron with the protonic transport numbers of 0.945-0.916 from 800 to 900 ℃. In wet air, the material was a mixed conductor of proton, oxide ion and electronic hole. The protonic transport numbers were 0.013-0.003, and the oxide ionic transport numbers were 0.346-0.265. Under hydrogen-air fuel cell conditions, the material was a mixed conductor of proton, oxide ion and electron, the ionic trans-port numbers were 0.945-0.848. The fuel cell could work stably, and at 900 ℃, the maximum power output density was 36.5 mW/cm2.     

Effect of doping elements on catalytic performance of CeO2-ZrO2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction （XRD） and Brunauer-Emmett-Teller （BET） techniques. The oxygen storage capacity （OSC） of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.     

Effect of yttrium on thermal stability and crystallization behavior of Nd60Fe20Al10Ni10 amorphous alloys

The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.     

Synthesis and anticancer properties of tungstosilicic polyoxometalate containing 5-fluorouracil and neodymium

A novel tungstosilicic polyoxometalate containing 5-fluorouracil and Nd,K26(C4H4FN2O2)8Nd(SiW11O39)4·SH2O(FNSW)was synthesized and its structure was characterized by using elemental analysis,FT-IR spectra,X-ray powder diffraction,UV-vis spectra and TG.The results indicated that the compound FNSW had Keggin structure of heteropolyanion and ring structure of 5-fluorouracil,and it had a good thermal stability.With 5-fluorouracil for the positive control group,the cytotoxicity tests in human renal embryonic cell HEK293 and the antitumor activity tests in hepatocellular carcinoma cell HepG-2 were carried out by the methyl thiazolyl tetrazolium method.The toxicity of the compound FNSW was lower than that of 5-fluorouracil,and compared with 5-fluorouracil the compound FNSW could inhibit HepG-2cell in vitro with significant difference.The rare earth clement Nd increased the biological activity of polyoxometalate significantly.     

Synthesis of Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Nano-Sized Powders by Low Temperature Combustion

The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.     

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.     

Effect of Yb_2O_3 Additive on Transformation Behavior of Anatase for TiO_2/(O′+β′)-Sialon Multi phase Ceramics

Structural and functional properties integration isbecoming one of the development tendencyinresearchfield of advanced ceramics during recent years,whichcan be performed by the incorporation of functionalphase into structural ceramic matrix and makes thematerials show excellent structural and functionalproperties si multaneously.Sialon is considered one of the most promisingstructural ceramics.Within this ceramic family,β′-Sialon shows distinguished comprehensive mechanicalproperties and O′…     

Microstructure and electrochemical properties of melt-spun Nd_(0.8)Mg_(0.2)(Ni_(0.8)Co_(0.2))_(3.8) hydrogen storage alloy

The effects of rapid solidification on the microstructure and electrochemical properties of Nd0.8Mg0.2(Ni0.8Co0.2)3.8 alloy were systematically investigated.The microstructure of alloys was characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD) and transmission electron microscopy(TEM).It was found that the melt-spun Nd0.8Mg0.2(Ni0.8Co0.2)3.8 ribbons became thinner and the average grain size of the ribbons became smaller with increasing wheel speed.A fraction of amorphous phase was observed for the ribbons melt-spun at high wheel speed(≥20 m/s).Microstructural characterization revealed that two phases:(Nd,Mg)2(Ni,Co)7 main phase(Ce2Ni7 type structure) and NdNi5 second phase(CaCu5 type structure),existed in the samples in cast state and melt-spun.The cycle stability of the melt-spun alloys was significantly enhanced as compared with cast alloy,and the sample prepared at wheel speed of 20 m/s exhibited good comprehensive electrochemical properties.