Humidity sensing properties of La~(3+)/Ce~(3+)-doped TiO_2-20 wt.% SnO_2 thin films derived from sol-gel method

The humidity sensing properties of La3+/Ce3+-doped TiO2-20 wt.%SnO2 thin films were studied.Sol-gel method was employed to prepare the films on alumina substrates.By constructing a humidity-impedance measuring system,the sensing behaviors were inspected for the films sintered at different temperatures.Experimental results showed that,0.5 wt.% of La2O3 or Ce2O3 doped films sintered at 500 °C for 2 h had the best humidity sensing properties,the impedance decreasing from 109 ? to below 104 ? in the humidity range of 15-95 RH%.Moreover,Ce3+-doping had better humidity sensing properties than La3+-doping.The doping mechanism was discussed in terms of phase composition,granularity of crystalline and segregation of rare earth ions at grain boundaries.     

Humidity sensing properties of Ce-doped nanoporous ZnO thin film prepared by sol-gel method

The humidity sensitive characteristics of the sensor fabricated from Ce-doped nanoporous ZnO by screen-printing on the alumina substrate with Ag-Pd interdigital electrodes were investigated at different sintering temperatures.The nanoporous thin films were prepared by sol-gel technique.It was found that the impedance of the sensor sintered at 600 oC changed more than four order of magnitude in the relative humidity(RH) range of 11%-95% at 25 oC.The response and recovery time of the sensor were about 13 and 17 s,respectively.The sensor showed high humidity sensitivity,rapid response and recovery,prominent stability,good repeatability and narrow hysteresis loop.These re-sults indicated that Ce-doped nanoporous ZnO thin films can be used in fabricating high-performance humidity sensors.     

Sol-gel preparation of La-doped bismuth ferrite thin film and its low-temperature ferromagnetic and ferroelectric properties

Bi0.85La0.15FeO3 thin film was prepared on ATO glass substrates by sol-gel technique. The effect of La doping on phase structure, film surface quality, ion valence, and ferroelectric/magnetic properties of Bi0.85La0.15FeO3 film were investigated. La dop-ing suppressed the formation of impurity phases and the transition of Fe3+ to Fe2+ ions at room temperature. Compared with the un-doped BiFeO3, La-doping also increased the average grain size and the film density, which resulted in the decrease of film leakage current density. The remanent polarization and saturation magnetization were enhanced significantly by La doping. The remanent polarization of Bi0.85La0.15FeO3 films gradually decreased while saturation magnetization increased with the decrease of measuring temperature within a range from 50 to 300 K.     

Multiferroic and in-plane magnetoelectric coupling properties of BiFeO_3 nano-films with substitution of rare earth ions La~(3+) and Nd~(3+)

Single-phase multiferroic BiFeO_3 and Bi_(0.9)(La/Nd)_(0.1)FeO_3(doped with rare earth ions La~(3+) and Nd~(3+)) films grown on(111)-Pt/Ti/SiO_2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric(ME) coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO_3 and Bi_(0.9)(La/Nd)_(0.1)FeO_3 exhabited a rhombohedral structure with(111) preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO_3 crystals, and it enhanced effectively the in-plane ME coupling(the ME coupling coefficient αE increased from 0.13 in the pure BiFeO_3 to 0.21 in Bi_(0.9)La_(0.1)FeO_3 and 0.34 V/(Oe·cm) in Bi_(0.9)Nd_(0.1)FeO_3). The mechanism of these phenomena was investigated systematically.     

Nano-tribological characteristics of lanthanum-based thin films on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Silane coupling reagent （3-mercaptopropyl trimethoxysilane （MPTS）） was prepared on silicon substrate to form two-dimensional Self-Assembled Monolayer （SAM） and the terminal -SH group in the film was in situ oxidized to -SO3H group to endow the film with good chemisorption ability. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM to form rare earth composite thin films （RE thin films）, making use of the chemisorption ability of the -SO3H group. Atomic Force Microscope （AFM）, X-ray Photoelectron Spectrometry （XPS）, and contact angle measurements were used to characterize the RE thin films. Adhesive force and friction force of the RE thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. The results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. To study the effect of capillary force, tests were performed in various relative humidities. The results showed that the adhesive force of silicon substrate increased with relative humidity and the adhesive force of RE thin films only increased slightly with relative humidity. Research showed that surfaces with higher hydrophobic property reveal lowered adhesive and friction forces.     

Effect of hydroxyl groups on hydrophilic and photocatalytic activities of rare earth doped titanium dioxide thin films

Rare earth(Y, La and Nd) doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction(XRD), atomic force microscopy(AFM), Fourier transform infrared(FTIR), optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains(40–60 nm), and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.     

Effects of Nd Doping on Magnetic-Optical Properties of GdFeCo Thin Films

The GdFeCo and NdGdFeCo thin films were prepared by sputtering, and their hysteresis loops, the temperature dependence of the saturation magnetization Ms and the magneto-optical Kerr spectrum in the visible light range were measured. By studying the effects of light rare earth element Nd doping on the magneto-optical Kerr rotation angle of GdFeCo thin films, it is found that proper Nd additives in GdFeCo films could enhance Kerr rotation at short wavelengths. So it could be better medium used as the readout layer of center aperture detection magnetically induced super resolution （CAD-MSR）.     

Investigation of Tribological Behavior of Lanthanum-Based Thin Films Deposited on Sulfonated Self-Assembled Monolayer

3-mercaptopropyl trimethoxysilane （MPTS） was prepared on glass substrate so as to form a two-dimensional self-assembled monolayer （SAM）, and the terminal - SH group in the film was in situ oxidized to - SO3H group to confer good chemisorption ability to the film. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM, making use of the chemisorption ability of -SOaH group. Atomic force microscopy （AFM） and X-ray photoelectron spectrometry （XPS） and contact angle measurements were used to characterize the thin films. The tribological properties of the as-prepared thin films sliding against a steel ball were evaluated on a friction and wear tester. Tribological experiment shows that the friction coefficient of glass substrate decreases from 0.8 to 0.08 after the rare earth （RE） self-assembled films （SAMs） are formed on its surface. And the RE self-assembled films have longer wear life （500 sliding passes）. It is demonstrated that RE self-assembled film exhibits good wear-resistant property. The marked decrease in friction and the longer wear life of RE films are attributed to the excellent adhesion of the film to the substrate and to the special characteristics of the RE elements. The frictional behaviors of RE thin-films-coated silicon surface were sensitive to the applied load and the sliding velocity of the steel ball.     

Effects of rare earth oxides on dielectric properties of Y2Ti2O7 series ceramics

A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on the microstructure and dielectric properties of Y2Ti2O7 ceramics were investigated. The experimental results showed that the rare earth ions were considered to dissolve in Y-sites of the pyrochlore structure, different rare earth oxides and concentration had different influences on Y2Ti2O7 cerami...     

Applications of X-ray fluorescence analysis of rare earths in China

A review was presented on the applications of X-ray fluorescence(XRF) analysis in Chinese rare earth industry during the last 20 years.The application consisted of the analysis of rare earth elements in ores and soil,concentrates,compounds,metals,alloys,functional materials,fast and online analysis in separation process,and so on.The analytical method was described on pressed powders,fused beads,liquid thin films and solid pieces.The detections of rare earth elements and compounds were concerned in iron and steel,nonferrous metals,petrochemical,geology,biology,electronic materials and other fields.     

Magnetocaloric effect and magnetic properties of La_（0.9）Ce_（0.1）（Fe_（0.99）Mn_（0.01））_（11.6）Si_（1.4）H_（1.6） compound

Magnetocaloric effect and magnetic properties of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 and its hydride La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 were investigated. The Curie temperature of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was increased by hydrogen absorption. XRD patterns showed that the structure of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 remained NaZn13-type. The Curie temperature (TC) of the sample was increased from 174 K to 331 K. The homogeneity of the hydrogen absorption for La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 was proven very well by the random measurement of DSC. The magnetic entropy △SM of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4H1.6 had peak at 326 K. The peak value of-△SM-was 12.3 and 7.8 J/(kg.K) under magnetic field change of 0-2 T and 0-1 T,respectively,which was comparable with Gd5Si2Ge2. The negative slope and inflection point of the Arrott curve indicated that the first-order magnetic transition of La0.9Ce0.1(Fe0.99Mn0.01)11.6Si1.4 was reserved after hydrogen absorption.     

Current-voltage characteristics with several threshold currents in insulating low-doped La1-xSrxMnO3 (x=0.10) thin films

The current-induced resistive switching behavior in the micron-scale pillars of low-doped La0.9Sr0.1MnO3 thin films using laser molecular-beam epitaxy was reported. It was demonstrated that the current-voltage curves at 120 K showed hysteresis with several threshold currents corresponding to the switching in resistance to metastable low resistance states, and finally, four closed loops were formed. A mode was proposed, which was based on the low-temperature canted antiferromagnetism ordering for a lightly doped insulating regime.     

Hydrothermal Synthesis and Characterization of Pyrochlore Titanate R2Ti2O7(R=Gd3+, Tb3+, Dy3+)

Pyrochlore titanate oxides, R2Ti2O7(R=Gd3+, Tb3+, Dy3+), were synthesized under mild hydrothermal conditions. The crystal growth of pyrochlore titanate oxides and taking place of chemical reaction in the hydrothermal processing were sensitive to the alkalinity, temperature, reaction time, the nature of the rare earth ion and the composition of initial reaction mixture. The as-prepared samples were characterized by powder X-ray diffraction, scanning electron microscopy, Raman spectrum and variable temperature dc magnetic susceptibility(Superconductivity quantum interference device, SQUIDS). The magnetic studies gave 7.29×10-23 A·m2/Gd3+ and -8.28 K, 8.75×10-23 A·m2/Tb3+ and -19.7 K, and 8.85×10-23 A·m2/Dy3+ and 0.84 K effective moments and Weiss constants for Gd2Ti2O7,Tb2Ti2O7 and Dy2Ti2O7, respectively.     

Luminescent and thermometric properties of dual emitting Eu~(2+)/Sm~(3+) co-doped Sr_4La(PO_4)_3O phosphor based on energy transfer

Eu²⁺/Sm³⁺co-doped dual-emitting Sr₄La(PO₄)₃O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu²⁺/Sm³⁺co-doped Sr₄La(PO₄)₃O phosphors were researched and analyzed in detail.The blue emission of Eu²⁺and the red emission of Sm³⁺can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr₄La(PO₄)₃O:Eu²⁺/Sm^(³⁺)phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr₄La(PO₄)₃O:Eu²⁺/Sm³⁺phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu²⁺and Sm³⁺ions.     

Electrochemical Preparation of La—Fe Alloy Films in Dimethylsulfoxide（DMSO）

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Growth,structure and spectral characteristics of KEr_(0.1)Yb_(0.9)(WO_4)_2 laser crystal

The 10 at.% Er3+-doped KYb(WO4)2(KEr0.1Yb0.9(WO4)2) laser crystal with dimensions up to 25 mm×15 mm×10 mm was grown by the Kyropoulos method.The crystal structure was identified as β-KEr0.1Yb0.9(WO4)2 by XRD analysis.Through TG-DTA curves,the melting point and transition point of the crystal were determined to be 1058 and 1031 °C,respectively.Infrared spectrum and Raman spectrum were measured,and the vibration frequencies of infrared and Raman active modes for the crystal were assigned.The absorption cross section is 3.1×10-20 cm2 at chief peak of 981 nm with the absorption line width of 26 nm.Based on the Judd-Ofelt theory,the intensity parameters ?λ(λ=2,4,6) calculated were:?2=16.34×10-20 cm2,?4=4.18×10-20 cm2,and ?6=1.26×10-20 cm2.There was a strong emission peak near 1533 nm and the emission line width at the main peak at 1533 nm run up to 55 nm with the emission cross section of 3.47×10-20 cm2 .These optical parameters indicated the potential of this crystal used as an excellent laser material for 1540 nm nearby human-eye safe.     

Thermoelectric properties of Sr0.9La0.1TiO3 and Sr2.7La0.3Ti2O7 with 15%Ag addition

15%Ag-added cubic perovskites Sr0.9La0.1TiO3 and Ruddlesden-Popper （RP） phases Sr2.7La0.3Ti2O7 were fabricated via hydrothermal synthesis, cold pressing and high-temperature sintering. The structure and thermoelectric properties were also investi-gated for all samples. The results indicated that Ag precipitated as a second phase. Ag addition made electrical conductivity and ab-solute Seebeck coefficient enhanced, as a result, the ZT values were enhanced both for two series. Compared with cubic perovskite, RP phase was subjected to smaller impact by Ag addition. The reasons for enhancing ZT value and the different impact for two series by Ag addition were also discussed.     

Effects of SrO/Li2O/La2O3/Ta2O5/TiO2-coating on electrochemical performance of LiCoO2

Commercial cathode material (LiCoO2) was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning elec-tron microscopy (SEM) and X-ray diffraction (XRD). The performance including cycling stability, diffusion coefficient under different volt-age, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor (Sr0.5La0.05Li0.35Ti0.5Ta0.5O3) and as a protecting shell to prevent LiCoO2 particles from be-ing attacked by the acidic electrolyte.     

One-step synthesis and structural quantitative analysis of La_(2/3)Sr_(1/3)MnO_3/La_(1.4)Sr_(1.6)Mn_2O_7 composites

La2/3Sr1/3MnO3/La1.4Sr1.6Mn2O7 composites with arbitrary weight percentage were prepared using a one-step solid-state reaction method. The experimental results demonstrated that addition of K2CO3 during preparation favored the formation of the composites even though the K+ ions were volatilized under the high temperatures of sintering. Full quantitative analysis with the Rietveld method showed that the content of La1.4Sr1.6Mn2O7 phase decreased and the fraction of the La2/3Sr1/3MnO3 phase increased as the a...