Ferroelectric properties of sol-gel derived Nd-doped SrBi4Ti4O15 thin films

Neodymium-doped strontium bismuth titanate （SrBi4-xNdxTi4O15） ferroelectric thin films were fabricated using the sol-gel method on Pt/Ti/SiO2/Si substrates. The influence of Nd content on the microstructure and ferroelectric properties of SrBi4-xNdxTi4O15 thin films were systematically studied. The results indicated that the SrBi3.88Nd0.12Ti4O15 （SBNT0.12） thin films had better ferroelectric properties, with a remanent polarization of （2Pr） of 34.3 μC/cm^2 and a coercive field （2Ec） of 220 kV/cm. This could be attributed to the fact that SBNT0.12 ferroelectric thin films consisted of more and larger ball-like grains, approximately 150-200 nm, with structure distortion, which greatly contributed to the improvement of the ferroelectric properties of the films. Furthermore, the film exhibited a good fatigue resistant property. The value of 2Pr after 10^10 switching cycles did not change significantly. The SrBi3.88Nd0.12Ti4O15 films were promising candidates for the application of FeRAMs.     

Photoluminescent properties of Ca2Gd8（SiO4）6O2： Dy^3＋ 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 various 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 material for the luminescence of various rare earth and mercury-like ions. In this article, Ca2Gd8（SiO4）6O2：Dy^3＋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 homogeneous particles. The Dy^3＋ showed its characteristic emission in crystalline phosphor films, i.e., ^4F9/2-^6H15/2 and ^4F9/2-^6H13/2.     

Ultraviolet-shielding and conductive double functional films coated on glass substrates by sol-gel process

Ultraviolet-shielding and conductive double functional films were composed of CeO2-TiO2 film and SnO2:Sb film deposited on glass substrates using sol-gel process.Ce(NO3)3·6H2O and Ti(C4H9O4),SnCl4 and SbCl3 were used as precursors of the two different functional films respectively.The CeO2-TiO2 films were deposited on glass substrates by sol-gel dip coating method,and then the SnO2:Sb films with different thickness were deposited on the pre-coated CeO2-TiO2 thin film glass substrates,finally,the substrates coated with double functional films were annealed at different temperatures.The optical and electrical properties of the CeO2-TiO2 films and the double films were measured by UV-Vis spectrometer and four probe resistance measuring instrument.The crystal structures and surface morphology of the films were characterized using XRD and optical microscope,respectively.The obtained results show that the ultraviolet-shielding rate of the glass substrates with CeO2-TiO2 films is not less than 90%,and transmittance in visible lights can reach 65%.With the thickness of the SnO2:Sb film increasing,its conductivity became better,and the surface resistance is about 260 Ω/ when the SnO2:Sb films were deposited 11 cycles of the dip on the pre-coated CeO2-TiO2 glass.The ultraviolet-shielding rate of the glass substrates with double functional films is higher than 97%,and the peak transmittance in the visible lights is 72%.Additionally,with increasing the heat treatment time,the Na+ of the glass substrates diffuses into the films,resulting in the particle size of SnO2 crystal smaller.     

Preparation and Characterization of Sol-Gel Derived Au Nanoparticle Dispersed Y2O3：Eu Films

Gold nanoparticles dispersed Y2O3 films were prepared through a sol-gel method by using yttrium acetate and Au nanoparticles colloid as precursors. The films were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and UV-VIS absorption spectra. XRD patterns and TEM images of Y2O3 ＋ Au films give the same resuits on structure and particle size as that of pure Y2O3 films. The surface plasma resonance （SPR） of Au nanoparticles in Y2O3 ＋ Au film was observed around 550 nm in the absorption spectrum and its position shifts to red with increasing annealing temperature is caused by the increase of dielectric constant of Y2O3 matrix and the size of Au nanoparticles. The second and third order nonlinear optical effects of Y2O3 ＋ Au films were also observed. The photoluminescent properties of Y2O3 ： Eu ＋ Au films were investigated and results indicate that there exist an energy transfer from Eu^3 ＋ to Au nanoparticles and this energy transfer decreases the emission of Eu^3 ＋ in Y2O3 ： Eu ＋ Au film.     

Properties of La0.9Sr0.1MnO3 and tourmaline compound catalytic materials for methane combustion

A novel catalytic material Lao.9Sr0.1MnO3 and tourmaline compound catalytic material was synthesized in the base of traditional catalytic material La0.9Sr0.1MnO3 which exhibited excellent catalytic activity for methane combustion. Different contents of toumaaline were added to give a series ofLa0.9Sr0.1MnO3 and tourmaline catalytic material through a sol-gel method. Samples above were characterized and analyzed by means of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Brunauer-Emmett-Teller method （BET）, temperaalre programmed reduction （TPR）, catalytic activity test and contact angle test. The as-prepared sample with 2% （m/m） tourmaline showed good homogeneity surface morphology and displayed the optimal catalytic activity. The light-off temperature reduced by 10 ℃ and the T90 decreased by 15 ℃. In addition, the mechanism of the reinforcement of catalytic activity was explored.     

Preparation of La MnO_3/graphene thin films and their photocatalytic activity

A novel photocatalyst of La MnO3/graphene thin films with the perovskite-type was synthesized by sol-gel process assisted with spin-coating methods on glass substrates.The prepared samples were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Brumauer-Emmett-Teller(BET) surface area analyzer, X-ray photoelectron spectroscopy(XPS) and UV-vis diffuse reflectance spectroscopy.Results showed that after the introduction of graphene, the perovskite structure was unchanged and the size of La MnO3 particles was about 22 nm, which uniformed growth in graphene sheet.Determination of contact angle indicated that the contact angle of glass substrate decreased and the hydrophilicity improved after treating with H2SO4 and APTES.The UV-Vis photocatalytic activity of the photocatalysts was evaluated by the degradation of diamine green B.La MnO3/graphene thin films had better photocatalytic ability than La MnO3 and Ti O2 films.The obtained k was 0.5627 and 0.3441 h–1 corresponding to La MnO3/graphene films and Ti O2 films, respectively.     

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.     

Introduction manner of sulfate acid for improving the performance of SO_4~(2–)/CeO_2 on selective catalytic reduction of NO by NH_3

A series of sulfated CeO_2 catalysts were synthesized by impregnation and sol-gel methods and used for selective catalytic reduction(SCR) of NOx by NH_3. The results showed that the sulfated CeO_2 catalysts prepared by sol-gel method showed excellent catalytic activity at 150–450 °C, and more than 90% NOx conversion was obtained at 232–450 ℃ with a gas hourly space velocity of 60000 h~(–1). The catalysts were characterized by X-ray diffraction(XRD), N_2 adsorption, Raman, thermogravimetry(TG), H_2-temperature-programmed reduction(H_2-TPR) and Py-infrared spectroscopy(Py-IR). The excellent SCR performance was associated with the surface acidity and the micro-structure. The introduction of sulfate acid into CeO_2 could increase the amount of Br?nsted and Lewis acid sites over the catalysts, resulting in the improvement of the low temperature activity. The sulfated CeO_2 catalysts prepared by sol-gel method possessed lower crystallization degree, excellent redox property and larger specific surface areas, which were responsible for the superior SCR performance.     

Microstructure and properties of Sm-substituted BiFeO3 ceramics

Bi1-xSmxFeO3 （x=0.00-0.15） ceramics were synthesized by sol-gel technique with rapid liquid phase sintering process to study the effects of samarium （Sm） substitution on their microstructure and properties. X-ray diffraction （XRD） and Raman studies showed that the structure of BiFeO₃ was changed from rhombohedral to orthorhombic at the samarium substitution concentration about x=0.10. The SEM investigation suggested that the Sm substitution hindered the grain growth. Magnetic measurements showed that all the samples studied had a weak ferromagnetism, and the ferromagnetic property of BiFeO3 was improved by Sm substitution due to the suppressed or broken cycloid spin structure caused by the changes in the crystalline structure and size effect. The leakage current was found to be reduced with increasing Sm concentration. The dielectric and ferroelectric measurements showed that dielectric constant, dielectric loss and ferroelectric properties were strongly dependent on the Sm content, Sm substitution could significantly improve the dielectric constant, remnant polarization and decrease the dielectric loss due to the significant decrease of the electric leakage of the samples.     

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.     

Crystal structure,microstructure and magnetic properties of SmCo-based films treated by different annealing methods

Effect of conventional thermal annealing(CTA) and rapid recurrent thermal annealing(RRTA) processes on crystal structure,mi-crostructure,and magnetic properties of the SmCo-based films were investigated.The results indicated that the CTA-treated films exhibited poor permanent magnetic properties,and a low intrinsic coercivity of 72.8 kA/m was observed.Wide hysteresis loop was obtained for the RRTA-treated films,providing better permanent magnetic properties.The intrinsic coercivity reached 312.0 kA/m.According to the X-ray diffraction(XRD) and atomic force microscopy(AFM) results,the magnetic properties of the CTA-treated films and RRTA-treated films were found to be correlated with the crystal structure and microstructure,which were strongly determined by the annealing treatment.CTA treatment led to poor crystallization effects for the films,and a rough surface(RMS=3.47 nm and P-V=35.42 nm) and large grain size of 92.7 nm were observed correspondingly.However,the RRTA treatment exhibited great contributions on the crystallization of the films,which is accountable for the smooth surface(RMS=2.047 nm and P-V=16.43 nm) and fine grain size of 60.8 nm.     

Effects of precipitate aging time on the cerium-zirconium composite oxides

Cerium-zirconium composite oxides with high performance were synthesized by a co-precipitation method, using zirconium oxychloride and rare earth chloride as raw materials. The effects of precipitate aging time on the properties of cerium-zirconium composite oxides were investigated. The prepared cerium-zirconium composite oxides were characterized by X-ray diffraction（XRD）, BET specific surface area, pulsed oxygen chemical adsorption, H2 temperature-programmed-reduction（H2-TPR）, scanning electron microscopy（SEM）, etc. The results showed that the precipitate aging time caused great effects on the properties of cerium zirconium composite oxides. With the increase of aging time, the cerium zirconium composite oxides showed enhanced specific surface area, good thermal stability, and high oxygen storage capacity（OSC）. The best performance sample was obtained while the precipitate aging time up to 48 h, with the specific surface area of 140.7 m2/g, and OSC of 657.24 μmolO2/g for the fresh sample. Even after thermal aged under 1000 oC for 4 h, the aged specific surface area was 41.6 m2/g, moreover with a good OSC of 569.9 μmolO2/g.     

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.     

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.     

Preparation and performance research of Ce-TiO2/KL ball photocatalysts

The Ce-TiO2/KL （diatomite） ball photocatalyst was prepared and characterized based on the pretreated diatomite. The resuits showed that comparing with the crude diatomite, proper pretreatment could significantly improve its SiO2 purity and specific surface area. The surface of diatomite was clear with uniform pore structure and big pore size. With diatomite ball as carder, the supported Ce-TiO2/KL ball photocatalyst was prepared by sol-gel method. The photocatalytic performances of the supported Ce-TiO2/ KL ball and Ce-TiO2/KL powder photocatalysts under various preparation conditions were studied in view of photocatalytic degrada- tion rate of Rhodamine B （Rh B） solution. The degradation rate of the ball photocatalysts for Rh B reached 94.6% and could be reused for many times, which showed much better photocatalytic performance and stability than powder photocatalysts.     

Effects of sol-gel method and lanthanum addition on catalytic performances of nickel-based catalysts for methane reforming with carbon dioxide

The nickel-based catalysts were prepared by the sol-gel method and used for the CH4 reforming with CO2. The effects of the sol-gel method on the specific surface area, catalytic activity, desorption, and reduction performances of catalysts were investigated with BET, TPR, and TPD. Compared with the catalyst prepared by the impregnation method, the results indicated that the catalysts prepared by the sol-gel method had larger specific surface area, showing higher catalytic activities and exhibiting perfect desorption and reduction performances. In addition, the modification effects of adding La were studied, and it was found that the 0.75NLBT catalyst constituted of 5wt.%Ni-0.75wt.%La was optimal.     

Effects of sol-gel method and lanthanum addition on catalytic performances of nickel-based catalysts for methane reforming with carbon dioxide

The nickel-based catalysts were prepared by the sol-gel method and used for the CH4 reforming with CO2. The effects of the sol-gel method on the specific surface area, catalytic activity, desorption, and reduction performances of catalysts were investigated with BET, TPR, and TPD. Compared with the catalyst prepared by the impregnation method, the results indicated that the catalysts prepared by the sol-gel method had larger specific surface area, showing higher catalytic activities and exhibiting perfect desorption and reduction per-formances. In addition, the modification effects of adding La were studied, and it was found that the 0.75NLBT catalyst constituted of 5wt.%Ni-0.75wt.%La was optimal.     

Redox behaviors and structural characteristics of Mn0.1Ce0.9Ox and Mn0.1Ce0.6Zr0.3Ox

Mn0.1Ce0.9Ox and Mn0.1Ce0.6Zr0.30x samples synthesized by sol-gel method were tested for redox properties through the dynamic oxygen storage measurement and characterized using X-ray diffraction, BET, electron paramagnetic resonance, and X-ray photoelectron spectroscopy. The results showed that redox performances of ceria-based materials could be enhanced by synergetic effects between Mn-O and Ce-O. Fresh and aged samples were characterized with the fluorite-type cubic structure similar to CeO2, and furthermore, the thermal stability of Mn0.1Ce0.9Ox materials was improved by the introduction of some Zr atoms. From XPS, it could be concluded that Mn^2＋/Mn^3＋ redox couples existed on the surface of Mn0.1Ce0.9Ox and Mn0.1Ce0.6Zr0.3Ox samples. Electron paramagnetic resonance researches revealed that there were three types of Mn^2＋ species： isolated Mn^2＋ substituting for Ce^4＋ ions in the lattice with a cubic symmetry, ones in defect with a noncubic symmetry, and at the surface of samples.     

Microstructure and Properties of Lao.7 Sr0.3 MnO3 Films Deposited on LaAlO3 （100）, （110）, and （111） Substrates

A comparative study of the crystalline structure, magnetic properties, and transport properties of LSMO films grown on （100）-, （110）-, and （111） LaAlO3（LAO） substrates was carried out. Using atomic force microscopy, round, rectangle, and dot surface morphologies were observed in （ 100）-, （ 110）-, and （ 111 ）-oriented LSMO films, respectively. Electrical and magnetic characterizations were performed on LSMO films of different orientation to provide evidence for the effect of strain on the magnetotransport properties. The （ 111 ）-oriented LSMO film has higher saturation magnetization and lower resistance compared with the （100）- and （110）-oriented LSMO films, which results from the smaller elastic deformation due to the larger elastic modulus along the 〈 111 〉 crystallographic direction.     

Preparation of high performance YGdBCO films by low fluorine TFA-MOD process

YBCO films doped with different contents of gadolinium(Gd) were prepared by the low-fluorine(low-F)trifluoroacetate metal-organic deposition(MOD) method.The effects of flow rate and holding time of the firing(crystallization) stage on the superconducting properties of Y_xGd_(1-x)Ba_2 Cu_3 O_(7-δ)(YGdBCO) films were investigated.The phase formation and texture were characterized by the X-ray diffraction(XRD),which indicate that severe degradation of the microstructure will be induced with the inappropriate flow rate.The surface morphology and element distribution were investigated by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results show that increasing the holding time of the firing stage is effective for the further decomposition of residual impurity phase on the surface.The mechanisms of the phase and surface evolution are also discussed.Finally,a high critical current density(J_c) value of 5.4 MA/cm~2 was achieved in the Y_(0.9)Gd_(0.1)BCO film fabricated by the cooperative control of the flow rate and holding time of the firing stage,which are contributed to the formation of excellent texture,homogeneous microstructure and dense surface of the YGdBCO films.