A Study on the Standard Free Energy of Formation of LaNi_5 and CeNi_5

The temperature dependence of standard free energy of formation of LaNi_5,CeNi_5 has been de-termined by galvanic—cell technique using 0.95LaF_3·0.05CaF_2 polycrystalline solid electrolyte.The cellused can be expressed as:Mo|La,LaF_3|0.95LaF_3·0.05CaF2|LaNi_5,Ni,LaF_3|Mo(903～1173K)Mo|La|0.95LaF_3·0.05CaF_2|LaNi_5,Ni|Mo(903～1173K)Mo|Ce,CeF_3|0.95LaF_3·0.05CaF_2|CeNi_5,Ni,CeF_3|Mo(873～1023K)The experimental results are as follows:△G_(f,LaNi_5)~0=-152590+13.143T±150 J/mol(903～1173K)△G_(f,CeNi_5)~0=-157600+25.514T±150 J/mol(873～1023K)     

Catalytic graphitization of carbon/carbon composites by lanthanum oxide

Graphitized carbon/carbon composites were prepared by the process of catalytic graphitization with the rare-earth catalyst, lantha-num oxide (La2O3), in order to increase the degree of graphitization and reduce the electrical resistivity. The modified coal tar pitch and coal-based needle coke were used as carbon source, and a small amount of La2O3 was added to catalyze the graphitization of the disordered carbon materials. The effects of La2O3 catalyst on the graphitization degree and microstructure of the carbon/carbon composites were investi-gated by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results showed that La2O3 promoted the formation of more perfect and larger crystallites, and improved the electrical/mechanical properties of carbon/carbon composites. Carbon/carbon compos-ites with a lower electrical resistivity (7.0 ???m) could be prepared when adding 5 wt.% La2O3 powder with heating treatment at 2800 oC. The catalytic effect of La2O3 for the graphitization of carbon/carbon composites was analyzed.     

Modification of Ag-doped BaTiO₃ powders through La gaseous penetration route

The Ag-doped BaTiO3(BATO) polycrystalline powders were fabricated by Sol-Gel method. Further modification by rare earth La was done through gaseous penetration route. Changes in constitution,structure,and electrical conductivity before and after modification of Ag and La were characterized. The acceptor dopant Ag owned the ability to decrease the resistivity of the doping samples from 4.30×109 Ω·m to 6.14×105 Ω·m where the resistivity fell by 4 orders of magnitude when the Ag doping ratio was 0.10%. And more doping of Ag enhanced the resistivity dramatically even beyond 2.0×107 Ω·m. Yet,gaseous penetration of La successively reduced the resistivity of BATO to the lowest point of 2.45×105 Ω·m. XRD analysis indicated that the doping process of Ag did not change the perovskite structure and main phases of the powders. However,new compound BaLa2O4 generated from complex reactions during the penetration process,which manifested that La3+ penetrated into the crystal lattices in the form of substituting the Ti4+ site. And this substitution strengthened the Ti-O bond,which led to the inhibition of blue shift in FTIR spectrum caused by doping of Ag. The morphology of La penetrated BATO powders detected by SEM and EDAX suggested that La did penetrate into the powders and this penetration process progressed the partly sintering of the powders which is in favor of the conductivity.     

Photoluminescent properties of Ca2Gd8(SiO4)6O2: Dy3+ phosphor films prepared by sol-gel process

There are growing interests on phosphor thin films owing to their potential application in high-resolution devices such as cathode ray tubes and flat panel display devices. The solution-based sol-gel method is one of the most important techniques for the synthesis of vari-ous functional coating films. Compounds with the apatite structure are very suitable host lattices for various luminescent ions. Ca2RE8(SiO4)6O2 ( RE=Y, Gd, La ) is a kind of ternary rare-earth-metal silicate with oxyapatite structure, which has been used as host mate-rial for the luminescence of various rare earth and mercury-like ions. In this article, Ca2Gd8(SiO4)6O2:Dy3 phosphor films were dip-coated on quartz glass substrates through the sol-gel process. X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectra, as well as lifetimes were used to characterize the resulting films. AFM study revealed that the phosphor films consisted of homoge-neous particles. The Dy3 showed its characteristic emission in crystalline phosphor films, i.e., 4F9/2–6H15/2 and 4F9/2–6H13/2.     

Humidity sensing properties of La^3＋ and K^＋ co-doped Ti0.9Sn0.1O2 thin films

The humidity sensing properties of La3+ and K+ co-doped Ti0.9Sn0.1O2 thin films were investigated. The humidity sensitive thin films were prepared by sol-gel method on alumina substrates. The sensing behaviors of thin films were inspected at different sintering temperatures by constructing a humidity-impedance measuring system. It was found that the addition of rare earth ion La3+ and alkali ion K+ was beneficial for improving the humidity sensitive properties of the samples and La0.003K0.5Ti0.9Sn0.1O2 sintered at 500 ℃ for 4 h showed the best humidity sensing properties. The impedance of this thin film decreased from 109 to 104 Ω with excellent linearity in the humidity range of 11%-95%. Narrow hysteresis loop, prominent stability and high sensitivity were obtained. The effects of dopant con-tent and doping mechanism on humidity sensitivity were also discussed in terms of segregation of rare earth ions at grain boundaries and granularity of crystalline and influence of K+ on the decrease in the intrinsic resistance of the materials, and increase in the number of wa-ter adsorption sites.     

Novel self-assembled films of La-based phosphonate 3-aminopropyltriethoxysilane

Silane coupling reagent (3-aminopropyltriethoxysilane (APTES)) was prepared on single-crystal silicon substrates to form two-dimensional self-assembled monolayer (SAM). The terminal-NH2 groups in the film were in situ phosphorylated to-PO(OH)2 group to endow the film with good chemisorption ability. Then La-based thin films were deposited on phosphorylated APTES-SAM in order to make good use of the chemisorption ability of-PO(OH)2 groups. The thickness of the film was determined with ellipsometer, while phase trans-formation and surface morphology, surface energy, phase composition were analyzed by means of atomic force microscope (AFM), contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that the terminal -NH2 groups could be completely transformed into desirable-PO(OH)2 groups after phosphorylation of APTES-SAM. Detailed XPS analysis of the La3+ peaks revealed that lanthanum element existed in the films in different states. As a result, conclusion could be made that lanthanum reacted with-PO(OH)2 groups on the surface of the substrate by chemical bond which would improve the bonding strength between the film and silicon substrate.Since the La-based thin films were well adhered to the silicon substrate, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).     

Phase control of magnetron sputtering deposited Gd2O3 thin films as high-κ gate dielectrics

Gd2O3 thin films as high-κ gate dielectrics were deposited directly on Si（001） substrates by magnetron sputtering at a pressure of 1.3 Pa and different temperatures. X-ray diffraction results revealed that all the films grown from 450 to 570 ℃ were crystalline, and the Gd2O3 thin films consisted of a mixture of cubic and monoclinic phases. The growth temperature was a critical parameter for the phase constituents and their relative amount. Low temperature was favorable for the formation of cubic phase while higher temperature gave rise to more monoclinic phase. All the Gd2O3 thin films grown from different temperatures exhibited acceptable electrical properties, such as low leakage current density （JL） of 10-5 A/cm^2 at zero bias with capacitance equivalent SiO2 thickness in the range of 6-13 nm. Through the comparison between films grown at 450 and 570 ℃, the existence of monoclinic phase caused an increase in JL by nearly one order of magnitude and a reduction of effective dielectric constant from 17 to 9.     

Characterization of A-site excessive perovskite La0.7-xSmx＋0.02Ca0.3CrO3-δ

La0.7-xSmx+0.02Ca0.3CrO3-δ(0≤x≤0.4) powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction (XRD) patterns of samples after sintering at 1400℃ for 4 h were indexed as tetragonal structure. The relative densities were all above 96% although decreased slightly with the increasing content of samarium, indicating that the excessive A-site element was helpful to enhance their sinterability. Conductivities of the specimens in air increased with increasing content of samar-ium. The conductivity of La0.6Sm0.12Ca0.3CrO3-δ was 33.6 S/cm in air at 700 ℃ which was about 1.7 times as high as that of La0.7Ca0.3CrO3-δ (20.1 S/cm). Average thermal expansion coefficients (TECS) of the specimens increased from 11.06×10-6 to 12.72×10-6 K-1 when x in-creased from 0 to 0.4, and they were close to that of Y doped ZrO2 (YSZ). La0.7-xSmx+0.02Ca0.3CrO<3-δ>(0.1≤x≤0.3) were good choices for in-termediate temperature solid oxide fuel cells (IT-SOFCs) interconnect materials.     

Synthesis and Electrical Properties of La0.6M0.4FeO3-δ(M=Ca, Sr, Ba) as Cathodes for SOFCs

A series samples of La0.6M0.4FeO3-δ (M=Ca, Sr, Ba) perovskite-type oxides were prepared by glycine nitrate process (GNP). FTIR, TG-DSC, XRD and TEM techniques were used to characterize the chemical constitution, thermal stability and phase structure. The electrical conductivity of the samples was investigated by four-probe technique. With the increase of substituted-ionic radius, the temperature of phase formation increases, and the solid solubility decreases gradually, respectively. The La0.6Ca0.4FeO3-δ(LCF)powder is pure cubic perovskite-type crystalline after fired at 850 ℃ for 2 h. The XRD patterns of La0.6Sr0.4FeO3-δ(LSF) powder shows a small quantity of SrO peaks sintered at 1050 ℃ for 2 h. The electrical conductivity of LCF and LSF at 500～800 ℃ is over 100 S·cm-1, and the value of LCF is 1170 S·cm-1 at 800 ℃, which indicate that LCF and LSF may be used as a profitable cathode for IT-SOFCs. The characteristic of La0.6Ba0.4FeO3-δ(LBF) is poor, and the electrical conductivity at intermediate temperatures is 1/20 less than that of LSF.     

High Temperature Performances of Spherical Nickel Hydroxide with Additive Y2O3

The effect of Y2O3 as additive to the positive electrode on the high-temperature performances of the Ni-MH batteries was studied. The specific capacities of the positive electrode in Ni-MH battery at higher temperatures are much lower than usual. In order to improve high-temperature performances, charge/discharge curves of the Ni(OH)2 electrodes with different amounts of Y2O3 at different temperatures were studied. It is found that the specific capacities of the spherical Ni(OH)2 with Y2O3 as additive are much higher than those of the regular at higher temperatures. The specific capacity of Ni(OH)2 containing 1% Y2O3 at 0.2C C/D rate is 35% higher than that of the reguiar. The specific capacity of Ni(OH)2 containing 0.2% Y2O3 at 1C C/D rate is 15% higher than that of the regular. Mechanism of Y2O3 improving high temperature performances of Ni(OH)2 electrode was also discussed in detail.     

Synthesis of Yb:Lu_3Al_5O_(12) nano powders with the reverse strike co-precipitation method:influence of decomposition of NH_4HCO_3

Yb:Lu_3Al_5O_(12)(Yb:LuAG) nano powders were synthesized with the co-precipitation method from cation(Lu~(3+),Yb~(3+),Al~(3+)) solution of different concentrations using NH_4HCO_3 as the precipitant.The influence of cation concentration on the morphology and purity of the calcined powders was studied.Contrary to the conventional suggestion that recommends thin solution to obtain loosely agglomerated nano powders,results showed that thin cation(Lu+Yb+Al) concentration≤0.08 mol/L led to formation of Al_2O_3 and LuAP impurities in the obtained nano powders.By means of Tg/(DTA),X-ray diffraction(XRD),scanning electron microscopy(SEM),the cause was revealed to be re-dissolution of Lu at high pH value that resulted from the decomposition of NH_4HCO_3.(Lu+Yb+Al) concentration of ~0.24 mol/L was recommended to achieve pure Yb:LuAG nano powders.Transparent Yb:LuAG ceramics were fabricated with the prepared Yb:LuA G nano powders.The transmittance around 800 nm was 77.5%.     

Effects of oxygen pressure on La_3Ga_5SiO_(14) thin films grown by pulsed laser deposition

La3Ga5SiO14 thin films were grown on Si(100) substrates by pulsed laser deposition at several oxygen pressures(5,10,and 20 Pa).The effects of oxygen pressure on the structural and morphological characteristics of the films were investigated using X-ray diffraction,atomic force microscopy,and scanning electron microscopy.X-ray diffraction results showed the intensity of lines from crystallites oriented along the(300) and(220) planes increased as the oxygen pressure was increased to 20 Pa.The deposited films ...     

Influence of Bath Composition on Magnetic Properties of Electrodeposited Co-Pt-W Thin Films

Effect of bath composition （[Co^2＋]/[-Pt^Ⅳ ] and [-WO4^2- ], [cit^-]） and pH on the magnetic properties of electrodeposited Co-Pt-W thin films has been investigated. Electrodeposited Co-Pt-W thin films exhibited strong perpendicular magnetic anisotropy when the ratio of [-Co^2＋ ] to [-Pt^Ⅳ ] was 10 ; cathode current efficiency and perpendicular magnetic anisotropy showed little variations when [WO4^2- ] was lower than 0. 1 mol/L, but perpendicular magnetic anisotropy had strengthened when [WO4^2-] was over 0. 1 mol/L, which could be explained by the fact that the hydrogen evolution could produce pores as magnetic domain pinnings; citrate as complexing reagent can promote the polarization of [Co^2＋] and [Pt^Ⅳ]. As a result, the equilibrium electrode potentials of cobalt and platinum moved to negative direction, which led to the co-deposition of Co, Pt, and W. It was also found out that the as-deposited Co- Pt-W hard magnetic thin films were very homogeneous, smooth, and had the maximum coercivity for the bath pH 8. 5 and the concentration of citrate 0. 26 mol/L.     

Scaling Behavior and Magnetic Properties for SmxCo5 Films

SmxCo5 (x=1.3, 0.7, 0.4) thin films were prepared by magnetron co-sputtering technique. The samples were annealed at 723 K under Ar atmosphere. The annealed time was chosen as 30 min. The hysteresis loops of the samples were measured under the ac applied magnetic field with the period Tp (2π/ω), H(t)=H0sin(ωt), by vibrating sample magnetometer (VSM). The experimental results indicate that, (1) the average hysteresis loop areas as functions of the values of H0 and ω display a power scaling law with the exponents, A=A0 H0αωβ; (2) the x composition of SmxCo5 film has evident effect on the scaling behavior and magnetic properties; (3) the anisotropy scaling exponents exist clearly in the anisotropy SmxCo5 thin films. Moreover, the scaling behavior of the anisotropy magnetic film was also simulated with Monte Carlo method. The simulated results are consistent with the experimental fact.     

Thermal Stability and Tribological Properties of Fluorinated Amorphous Carbon Thin Films Doped With Nitrogen

Nitrogen doped fluorinated amorphous carbon thin films（a-C:N:F）were prepared by radio frequency plasma enhanced chemical vapor deposition（rf-PECVD）under different deposited condition using CH4,CF₄,and N₂ as source gases.The thin films were annealed at different temperature.The influence of doped nitrogen on the chemical structure,tribological and thermal properties of thin films were investigated by Atomic force microscopy（AFM）,Fourier transform infrared absorption spectrometry（FTIR）,X-ray photoelectron spectrum spectra（XPS）,and thermogravimetry（TG）.The results indicated that the thin films presence a compact and smooth morphology surface after the nitrogen doped.After incorporation of nitrogen,the H atoms are replaced partially by the N atoms in the thin films.The degree of cross-linking of the carbon network in the thin films is enhanced.The chemical bonds of C=N,C≡N,and C-Nx（x=1,2,3）have formed in the films.The relative content of sp² graphite phase increases.The thermal stability temperature of the films deposited atγ=0.5（γ=N₂/[CF₄+CH₄+N₂]）is 420℃.The tribological properties improve greatly,and the friction coefficient of the a-C:N:F thin films ranges approximately from 0.20 to 0.36.     

To Explore High Magnetoelectrochemical Chirality

Cu films were electrodeposited under a magnetic field of 5 T on the Pt disc electrodes with diameters of 3 mm~25μm.Such magnetoelectrodeposited(MED)Cu films were employed as an electrode,and cyclic voltammograms were measured for the electrochemical reactions of an amino acid of alanine.Chiral behavior was observed as oxidation current difference between the enantiomers.Clear magnetoelectrochemical chirality was observed on the micro-disk electrode and on the kinetic-controlled electrode process of alanine.The chiral response was durable for more than 10cycles of the consecutive voltammetric measurements of the enantiomers.     

A strategy for improving sinterability and electrical properties of gadolinium-doped ceria electrolyte using calcium oxide additive

In this study,Gd and Ca co-doped ceria electrolytes with the compositions of Ce_(0.8)Gd_(0.2-x)Ca_xO_(2-δ)(x=0-0.08) were prepared by a novel gel-casting method.The effects of the addition of Ca on the phase compositions,sintering behavio r,and electrical prope rties of samples were investigated.According to the scanning electron microscope results and relative density measurement results,it is found that the addition of particular quantity of CaO can promote the sintering densification with a uniform grain growth.When the sintering temperature is 1400℃,the sample with 6 mol% addition of Ca has the highest relative density,which reaches 98.5% of the theoretical density.The electrical properties testing results confirm that the electrical conductivity of the samples can be improved significantly by doping appropriate CaO content.The maximum conductivity of 0.082 S/cm can be obtained at 800℃ in the Ce_(0.8)Gd_(0.12)-Ca_(0.06)O_(1.87) sample.It suggests that CaO can be used as an effective sintering aid and a codopant on the optimization of electrical properties for ceria-based electrolytes.     

Fabrication of highly luminescent TiO2:Eu3+ thin film with low annealing temperature requirement by co-doping with Sn4+ ions

Rare earth(RE)-doped TiO₂ thin films possess important applications in modern optoelectronic devices.However,the high annealing temperature requirement remains a critical restriction in device fabrications.In this work,TiO₂ thin films doped with trivalent europium(Eu³⁺) ions were fabricated by a convenient sol-gel approach and subsequent annealing treatment.Interestingly,it is found that the optimal post-annealing temperature of TiO₂:Eu³⁺thi...     

Competition between Band Filling and Steric Effect in Ordered Double Perovskites Sr2- x Lax MnMoO6

The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.     

Structural and mechanical properties of La_(1/3)NbO_3 and La_(1/3)TaO_3 thin films prepared by chemical solution deposition

In this work, properties of perovskite lanthanum niobate La_(1/3)NbO_3(LN) and tantalate La_(1/3)TaO_3(LT)transparent thin films(~200 nm thickness) prepared by chemical solution deposition on Pt/SiO_2/Si substrates were described. The precursors and films were analyzed using FTIR and XPS spectra, XRD and SEM imaging. The both films after annealing at 1100 ℃ contained perovskite phase with a small fraction of pyrochlore LaNb_5 O_(14)(in LN). The heterogeneous micro structure of LN film was composed from spherical or needle-like particles and homogeneous LT film that resulted in significant changes of their mechanical properties. The elastic modulus and hardness of these films were characterized for the first time by conventional and continuous stiffness(CSM) nanoindentation. The LT film modulus(E) and hardness(H) were higher(~105.7 and 5.3 GPa) than LN(~91.5 and 3.8 GPa). The effect of microstructure on mechanical properties is significant. In addition, the average Derjaguin-Muller-Toporov(DMT)-based elastic modulus of LN film surface were estimated ~50 GPa using AFM PeakForce QNM elastic mapping. The findings presented here can contribute to the fabrication of LN and LT films for the application to electrolytic thin film devices.