[Y(dbm)_3(H_2O)]:Synthesis,thermal behavior and spin-coating precursor for Y_2O_3 layer formation

The synthesis,structure and thermal behavior of [Y(dbm)_3(H_2 O)](3)(dbm = 1,3-diphenyl-1,3-propandionate) and its use as a spin-coating precursor for Y_2 O_3 deposition is reported. Complex 3 was prepared by the reaction of [Y(NO_3)_3·6 H_2 O](1) with 3 equiv of Hdbm(2) in presence of NaOH. The molecular structure of 3 in the solid-state was determined by single X-ray crystal diffraction. Both C_1 symmetric crystallographically independent species of 3 possess a YO7 coordination setup with minor deviation from an ideal capped octahedron coordination geometry(∧ enantiomer). Complex 3 forms a1 D chain, due to intermolecular hydrogen bonds between the coordinated H_2 O molecule and the 0 atom of the dbm ligand, respectively. The thermal decomposition behavior of 3 was investigated by thermogravimetric studies in the temperature range of 40-800 ℃ and 40-1300 ℃ under an oxygen and argon atmosphere, respectively. Powder X-ray diffraction(PXRD) measurements of the residues confirmed the formation of Y_2 O_3. Complex 3 was applied as a spin-coating precursor for yttrium oxide film formation on either Si wafers with a continuous 100 nm thick SiO_2 film, or with a native oxide layer.The as-deposited Y_2 O_3 layers are smooth, conformal, dense and transparent and are of a thickness of 27 and 30 nm, respectively.     

Tetranuclear yttrium and gadolinium 2-acetylcyclopentanoate clusters: Synthesis and their use as spin-coating precursors for metal oxide film formation for field-effect transistor fabrication

Lanthanide clusters [Ln_4(μ_3-OH)_2(η~2-accp)_4((μ-O)-η~2-accp)_6](Ln = Y(4),Gd(5); accp = 2-acetylcyclopentanoate) are accessible by treatment of [M(NO_3)_3·6 H_2 O](M = Y(1),Gd(2)) with 3 equiv. of Haccp(3) in presence of NaOH. The molecular structures of 4 and 5 in the solid-state are discussed. The thermal behavior of 4 and 5 was studied by TG under Ar and O_2, showing multistep decomposition processes. Additionally, DSC studies were carried out under an atmosphere of O_2. PXRD measurements of the TG residues confirm the formation of Ln_2 O_3.Spin-coating experiments were carried out with 4 and 5 for Ln_2 O_3 film deposition on silicon substrates. The layers are smooth, close and are of thicknesses of 18.87±1.13 nm and 25.59 ± 4.55 nm for Ln = Y and Gd, which was evidenced by SEM and EDX studies. Field-effect transistors were successfully fabricated by deposition of carbon nanotubes on top of the Y_2 O_3 films and formation of palladium contacts by a lift-off procedure. An on/off ratio of more than 4 orders of magnitude is achieved without considerable leakage currents. These results demonstrate the potential use of spin-coated Y_2 O_3 as a gate dielectric in electronic devices.     

Synthesis and structure of a praseodymium (Ⅲ) complex with carboxylate ligand:A thermal and spectroscopic study

One Pr(Ⅲ) lanthanide ion complex was initially synthesized and characterized by TGA-DSC in air atmosphere, as well as characterized by CHN elemental analysis, defining the stoichiometric ratio as Pr(DMBz)_3. The gaseous products evolved during the thermal decomposition were also monitored in N_2 atmosphere employing TGA/FT-IR system. A crystal structure is obtained by state-of-the-art powder X-rays diffraction methods measured in conventional laboratory equipment and refined by the Rietveld method, which defined it as a monoclinic system of the space group P2_1/C with a polymeric crystal structure, [Pr(DMB_Z)_3]_n. FT-IR theoretical spectrum and time-dependent density functional theory(TD-DFT) were calculated from TGA-DSC and crystalline system data. The experimental and theoretical FT-IR spectra present a high correlation degree when the main stretching bands are compared, while the energy transfer(HOMO — LUMO) in their neighborhoods suggests the main contributions of the light-emitting states.     

Thermal and transport properties of La_(2–x)Nd_xMo_2O_9

Single-phase La_(2–x)Nd_xMo_2O_9(0≤x≤1.8) compounds were prepared using solid-state reaction technique. Their structural and thermal p roperties were characterized by room and high temperatures X-ray diffraction(XRD), thermo gravimetric analysis-differential scanningcalorimetry(TG-DSC), and high temperature Raman spectra. The transport properties were investigated using D.C. four-probe technique and Hebb-Wagner polarization method. The substitution limit of Nb~(3+) in La_(2–x)Nd_xMo_2O_9 was determined to be in the range of 1.8x1.9, and the cubic lattice parameter of La_(2–x)Nd_xMo_2O_9 decreased linearly with the increasing of x. When the Nb~(3+) substitution content x was larger than 0.6, the α/β phase transition could be depressed to such a great degree that the phase transition thermal enthalpy was not detected by DSC. The temperature dependence of electrical conductivities for La_(1.4)Nd_xMo_2O_9 below 873 K and that for LaNdMo_2O_9 below 923 K obeyed the Arrhenius law, while above 873 and 923 K Vogel-Tammann-Fulcher(VTF) model could describe the conduction behaviors satisfactorily. The transition of transport mechanism from Arrhenius to VTF was caused by the change of structure, which was supported by the high temperature XRD and Raman results. The ionic transport number of La_(1.4)Nd_xMo_2O_9 in air was larger than 0.99 at 1073 K, and with the increasing of temperature it was close to 0.98 at 1173 K. In view of the phase transition, thermal expansion and conductivity properties, La_(1.4)Nd_xMo_2O_9 should be a promising electrolyte material in La_(2–x)Nd_xMo_2O_9 series.     

Synthesis,photoluminescence properties and thermal investigation by TG-MS of RE(DAS)_3·xH_2O(RE=Eu~(3+),Tb~(3+))

Rare earth(Ⅲ) diphenyl-4-amine sulfonates(RE(DAS)_3·xH_2O,RE=Eu~(3+),Tb~(3+))phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates.FTIR,TG/DSC coupled to mass spectrometry(TG/DSC/MS),X-ray powder diffraction(XPD),scanning electron microscopy(SEM) and photo luminesce nce(PL) spectroscopy were utilized to structurally and morphologically characterize the samples.Thermal decomposition of Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O at 973 K under dynamic air atmosphere results in crystalline Eu_2O_2SO_4 and Tb_2O_2SO_4 materials,respectively.Accordingly,MS spectra reveal the liberation of thermal decomposition products of precursors,largely as CO_2,NO_2 and SO_2 gases.The diphenyl-4-amine sulfonate(DAS) ligand demonstrats a good stabilizing property for Eu~(3+) and Tb~(3+) ions.The Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O compounds display efficient red and green emissions,under UV excitation,arising from the ~5D_0→~7F_J(J=0-4) and ~5D_4→~7F_J(J=0-6) transitions of the Eu~(3+) and Tb~(3+) ions,respectively.     

Effects of Cerium Oxide on Ni／Al2O3 Catalysts for Decomposition of CH4 and C2H4

Characteristics of carbon deposition of CH4 and C2H4 decomposition over supported Ni and Ni-Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal-semiconductor interaction (MScI) in the Ni-Ce catalyst, and the effect of MScI on the carbon deposition of CH4 decomposition is opposite to that of C2H4. A novel model of carbon deposition of CH4 or C2H4 decomposition was proposed.     

Cerium and ruthenium co-doped La_(0.7)Sr_(0.3)FeO_(3-δ) as a high-efficiency electrode for symmetrical solid oxide fuel cell

Symmetrical solid oxide fuel cells(SSOFCs) could be alternative energy conversion devices due to their simple fabrication process and low cost.Herein,perovskite La_(0.6)Ce_(0.1)Sr_(0.3)Fe_(0.95)Ru_(0.05)O_(3-δ)(LCSFR) was synthesized and evaluated as a high-performance electrode for SSOFCs based on the electrolyte of La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM).LCSFR retains their stable perovskite crystal structure in both reducing and oxidizing atmospheres,though a minor amount of LaSrFeO_4 phase is present under reducing conditions.Morphology investigation shows that homogeneously dispersed Ru metallic nanoparticles are exsolved on the surface of LCSFR after being reduced.The polarization resistance(R_p) of LCSFR-CGO(Ce_(0.9)Gd_(0.1)O_(2-δ)) is about 0.11 Ω·cm~2 at 800℃ in air,while the value of R_p for LCSFR-CGO in wet H_2(3% H_2 O) increases up to 0.32 Ω·cm~2.The symmetrical LCSFR-CGOILSGMILCSFR-CGO cell demonstrates a performance with an open circuit potential(OCV) of 1.07 V and a maximum peak power density of 904 mW/cm~2 at 800℃ using wet H_2 as the fuel.This high performance indicates that LCSFR is a candidate electrode for SSOFCs.     

Synthesis and characterization of monodisperse Eu~(3+) doped gadolinium oxysulfide nanocrystals

Gd_2O_2S:Eu~(3+) nanoparticles were synthesized using two step process consisting of sulfuration of basic carbonates obtained by homogenous precipitation.Annealing of lanthanide nitrates at total concentration of 5×10~(-3) mol/L in a water solution containing relatively high,three molar concentration of urea ensured the optimal conditions for the reproducible preparation of uniform and small spherical particles.During sulfuration step elemental sulfur was mixed with precursor which eliminated necessity of using an auxiliary furnace and provided sulfur-reach reaction atmosphere.Such optimized protocol afforded synthesis of spherical and non-agglomerated nanoparticles with diameter smaller than 100 nm.The precursors morphology was maintained,but particles size was reduced by 15%-20%during sulfuration.The results indicated that higher emission intensity was observed for Gd_2O_2S:Eu~(3+)(8%)oxysulfide sample synthesized using crystalline Gd(CO_3)OH precursor,than for that obtained from amorphous Gd_2(OH)_2(CO_3)_2·H_2O precursor,although some further efforts to improve morphology of the former are still required.     

Energy transfer and 2 μm emission in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders

(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders doped with various concentrations of Tm~(3+) and Ho~(3+) were prepared by the citrate method. The standard cubic Y_2O_3 phase can be matched in the Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2 O_3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm~(3+) to Ho~(3+) and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to ~3 F_4→~3 H_6 transition of Tm~(3+) and ~5 I_7→~5 I_8 transition of Ho~(3+), respectively.Better spectral properties were achieved in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm~(3+) and 1 mol% Ho~(3+).     

Dehydration,hydrolysis and oxidation of cerium chloride heptahydrate in air atmosphere

The thermal decomposition of CeCl_3·7 H_2 O was studied from room temperature to 800 ℃. Analysis was performed by applying TG-DTA, XRD, FESEM, EDXS, and TG-MS technologies to investigate the thermal decomposition mechanism of CeCl_3·7 H_2 O in air atmosphere. Multiple forms of hydrated cerium chloride compound were observed in the dehydration products. The CeCl_3 hydrolysis product was separated by a continuous centrifugation method and the phase composition was identified as CeO_2,Ce(OH)_3,and CeCl_3·4 H_2 O by XRD analysis. The evolved gas composition was identified as CI_2 and HCI by TG-MS system. Based on the analysis of the experimental results, the mechanism of thermal decomposition of CeCl_3·7 H_2 O was proposed with completion of the dehydration reaction at 224 ℃,the hydrolysis reaction at 170-480 ℃,and the oxidation reaction of CeCl_3 above 480 ℃.     

Photoluminescence and thermal quenching properties of tunable green-emitting oxynitride (Ca_xSr_(1–x))_6Si_(25.6)Al_(6.4)N_(41.6)O_(4.4):Eu~(2+) phosphors

Green emitting Eu~(2+) doped(Ca_xSr_(1–x))_6Si_(25.6)Al_(6.4)N_(41.6)O_(4.4) phosphors with x value ranging from 0 to 0.1 were synthesized by the solid state reaction method under nitrogen atmosphere.The X-ray diffraction(XRD)patterns of the phosphors with different Ca~(2+) concentrations indicated that pure sialon phases were obtained.Crystal structure of these sialon phases was estimated to be a commensurate composite network stacking by two different types of layers.Intense and tunable green emissions with a slight red shift from 515 to 520 nm were observed with varying Ca/Sr ratios.The emission intensity decreased gradually because of the increase of the crystal splitting effect.Thermal quenching properties of the phosphors with different Ca~(2+) saturation were also discussed.The thermal stability became worse as more Ca~(2+) ions substituted for Sr~(2+) ions according to a larger Stokes shift.The solid solution phosphors could be a promising candidate for white LEDs for their interesting photoluminescence properties when the thermal stability would be improved.     

Nitric oxide(NO) decomposition on catalysts,containing oxides of lanthanum and cerium,supported on γ-alumina

The present work was devoted to study the catalytic activity of lanthanum and cerium oxides separately,deposited on g-alumina in the reaction of decomposition of nitric oxide. The catalyst samples were prepared by the method of impregnation of g-Al_2 O_3 using solutions, containing nitrates of lanthanum and cerium. The prepared samples were calcined for 4 h at temperature 650℃ in an oven in air atmosphere. The catalysts were characterized by: chemical analysis by inductively coupled plasma atomic emission spectrometry(ICP-AES), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM) combined with energy-dispersive X-ray spectroscopy(EDS), electron paramagnetic resonance(EPR) and infrared(IR) spectroscopy, as well as measurement of the specific surface area. The results show that the catalysts based on lanthanum oxide and cerium oxide deposited on alumina display high catalytic activity over 60% conversion degree with respect to decomposition of nitric oxide in the absence of reducing agent. In the presence of reducer the activity reaches 90% conversion degree.     

Effects of La2O3/Li2O/TiO2- Coating on Electrochemical Performance of LiCoO2 Cathode

Conventional cathode material （LiCoO2） was modified by coating with a thin layer of La2O3/Li2O/TiO2 for improving its performance for lithium ion battery. The morphology and structure of the modified cathode material was characterized by SEM, XRD, and Auger electron spectroscopy. The performance of the cells with the modified cathode material was examined, including the cycling stability, the diffusion coefficient under different voltages, and the C-rate discharge. The results showed that the cell composed of the coated cathode material discharged at a large current density, and possesses a stable cycle performance in the range from 3.0 to 4.4 V. It was explained that the rate of Li ion diffusion increased in the cell while using La2O3/Li2O/TiO2-coated LiCoO2 as the cathode and the coating layer may act as a faster ion conductor （La2O3/Li2O/TiO2）.     

Synthesis and crystal structure of [Y(C_5Me_4SiMe_3){μ-O(CH_2)_3CH_3}{N(SiHMe_2)_2}]_2

A dimeric yttrium complex [Y(C5Me4SiMe3){μ-O(CH2)3CH3}{N(SiHMe2)2}]2 (1) was isolated as one of the byproducts from the reaction of Y{N(SiHMe2)3}3(THF)2 with C5Me4HSiMe3 in 1:1.1 molar ratio in toluene at 100 C for 2 d.Complex 1 was characterized by elemental analysis,NMR spectroscopy,FT-IR spectroscopy,and X-ray single crystal structure analysis.X-ray diffractions revealed that com-plex 1 was a symmetric dimer,and the center metal Y3+ was six-coordinated by one nitrogen atom from the amide group,two bridgi...     

On the existence of the compound “Ce_3NbO_(7+δ)” prepared under air atmosphere

The solid state synthesis of the phase "Ce_3 NbO_(7+δ)",from stoichiometric quantities of CeO_2 and Nb_2 O_5,was investigated under air atmosphere,as previously described by Zhang et al.(Journal of Rare Earths,2007,25,730-733),A combination of powder X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,and laboratory Ce L_3 X-ray absorption spectroscopy,demonstrates the product of the reaction to be a mixture of CeO_2 and CeNbO_4.These data,and reexamination of the published X-ray diffraction data of "Ce_3 NbO_(7+δ)",are consistent with this phase in fact being CeO_2.No evidence for the formation of a phase of composition "Ce_3 NbO_(7+δ)" is found,by solid state synthesis under air atmosphere.     

Synthesis,spectral characterization,thermal and biological studies of lanthanide(Ⅲ) complexes of oxyphenbutazone

Lanthanide(III) complexes of 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione(OPB) were prepared by homogeneous precipitation. The solid complexes were characterized by elemental analysis, magnetic susceptibility data, molar conductivity measurements and IR, UV-Vis, mass,1H NMR and13C NMR spectral methods. The thermal decomposition of the complexes under static air atmosphere was investigated by simultaneous TG/DTG at a heating rate of 10 °C/min. The final decomposition products were found to be metal oxides. The spectroscopic data suggested that OPB acted as a bidentate, mono-ionic ligand coordinating through two carbonyl oxygens of the pyrazolidinedione ring. The kinetic and thermodynamic parameters such as activation energy, pre-exponential factor and entropy of activation for each step of the decomposition reactions were evaluated using Coats-Redfern and MacCallum-Tanner equations. The negative entropy values of the complexes indicated that the activated complexes had a more ordered structure than the reactant and that the reactions were slower than normal. Investigations of antimicrobial activity of the compounds were carried out by the disk diffusion technique.     

Fe- and Co-doped lanthanum oxides catalysts for ammonia decomposition:Structure and catalytic performances

In this paper, a series of Fe- and Co-doped lanthanum(hydr)oxides catalysts were prepared by a simple coprecipitationhydrothermal method. The as-prepared catalysts were characterized with various techniques including powder X-ray diffraction(XRD), N_2 adsorption/desorption, inductively coupled plasma(ICP) and transmission electron microscopy(TEM). The Fe-based catalysts exhibited consecutive phase changes of amorphous Fe Ox→FeLaO_3→Fe_2N under different stages(as-prepared→calcination→ammonia decomposition reaction); as for Co-based catalysts, the phase transformation followed a sequence of Co(OH)_2→Co_3O_4→metallic Co. It was revealed that Fe_2N and metallic Co were most probably the active crystalline phase respectively for Feand Co-based catalysts in the decomposition of ammonia.     

Magnetic Properties and Surface Activity Sites of Pt-Dy/γ-Al_2O_3 Catalysts

The magnetism and surface behaviour of Pt-Dy/γ-Al_2O_3 catalysts were studied respectively bymeans of a Faraday magnetic balance and the method of carbon disulfide.The ferromagnetic impurity in thesupport,γ-Al_2O_3,at low temperature was corrected for the first time.The magnetic susceptibilities of the cat-alysts follow the sequence in different stage of preparation:χ_(uncalcined)<χ_(calcined)<χ_(reduced).The magnetic susceptibilities of the catalysts decrease as they adsorb hydrogen,cyclohexane or benzene.There is a correlation between the aromatization yield of cyclohexane or heptane on these catalysts and themagnetic susceptibility of the catalysts.Since addition of Dy increases the number of adsorption sites and therelevant proportions of weak adsorption sites,the abilities of sulfur-resistance and cyclohexanedehydrogenation are improved.In Pt-Dy/γ-A:_2O_3 catalysts,Dy improves the aromatization activity andstability of the catalyst and plays the role of the electron promoter.     

Effects of the precursor size on the morphologies and properties of γ-Ce_2S_3 as a pigment

Ceria spheres with different sizes and sulfurized products with corresponding morphology were prepared by hydrothermal and gas-solid reaction method at 600–800 °C under CS2 atmosphere for a short time, respectively. Dimensional effect in preparation of γ-Ce2S3 was firstly investigated by means of techniques such as scanning electron microscopy(SEM), X-ray diffraction(XRD), thermal gravimetric analysis(TGA) and spectrophotometer. The results showed that when ceria nanoparticles with small size were used as precursors, the γ-Ce2S3 could be prepared at the lower temperature and the badly sintered products were obtained; when ceria nanoparticles with large size were employed as precursors, pure γ-Ce2S3 was difficultly obtained even if the temperature was up to 800 °C and the products tended to keep their original size. The heat-resistance property of the γ-Ce2S3 with large size was better than the smaller one, and the pure γ-Ce2S3 prepared from precursor with small size had a good pigmentary performance.     

Synthesis of Cu/Ni-La_(0.7)Sr_(0.3)Cr_(0.5)Mn_(0.5)O_(3-δ) and its catalytic performance on dry methane reforming

In this study,Cu/Ni-La_(0.7)Sr_(0.3)Cr_(0.5)Mn_(0.5)O_(3-δ)(LSCM) catalysts were synthesized via the citric acid-nitrate process(CNP) and chemical co-precipitation. The catalytic performance of Cu/Ni-LSCM catalysts on dry methane reforming was evaluated in a fixed-bed reactor at 550/650 ℃ and atmosphere pressure. Cu/Ni loading was investigated as an influencing factor, which led to 5 cases of samples according to the different Cu/Ni mass ratios. The catalysts were characterized by X-ray diffraction(XRD), field emissionscanning electron microscope(FE-SEM), Brunauer-Emmett-Teller(BET) measurement, X-ray photoelectron spectroscopy(XPS), hydrogen-based temperature-programmed reduction(H_2-TPR) and thermos gravimetric analyzer(TGA). The results show that the methane conversion increases, the resistance against metal sintering increases and the carbon deposition drops after the copper is introduced. This optimum performance can be obtained under Case 3(Cu:Ni:LSCM = 1:3:6 in mass ratio).