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1.
KTa0.65Nb0.35O3(KTN) thin films were prepared by sol-gel process on Pt(111)/Ti/MgO(100) substrates from KOAc, Ta(OC2H5)5 and Nb(OC2H5)5 in ethanol. The KTN thin films had a prefferred (100) orientation on Pt(111)/Ti/MgO(100) substrates and contained a small amount of pyrochlore structure phase. The 0.8-m-thick KTN film showed a room-temperature relative permittivity of 2160 and a room-temperature dielectric loss of 0.0098 at 1.0 kHz. The maximum relative permittivity of the KTN film was 4232 at 294 K and 1.0 kHz. The remanent polarization and coercive field of the KTN film were 2.8 C/cm2 and 5.0 kV/cm, respectively, at 263 K.  相似文献   

2.
In this study, we prepared Sr x Ba1 – x Nb2O6 (x = 0.3, 0.5 and 0.7) thin film on 0.75 wt% La doped SrTiO3 (100) and (110) single crystal substrates. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)5 as raw materials, and acetic acid and diethlene glycol monomethyl ether as solvents. The substrates were coated with the solution by spin coating method. As-coated thin films were heated from 973 to 1273 K in air. The grains of the thin film on La doped SrTiO3 (100) were pillar shaped and arranged in right angle to each other. On the other hand, the grains of these thin films on La doped SrTiO3 were pillar shape and arranged in one direction. The crystallographic relationship of the thin film between Sr x Ba1 – x Nb2O6 and substrate that the 130 and 310 direction of the thin film on the substrate were oriented with c-axis in parallel to the substrate surface. On the other hand, (hk0) phase diffractions of Sr x Ba1 – x Nb2O6 thin film on the substrate (110) were investigated in the XRD theta-2theta measurement. It is expected that the Sr x Ba1 – x Nb2O6 (x = 0.3, 0.5 and 0.7) were highly oriented or epitaxial growing on La doped SrTiO3 (110) single crystal substrate.  相似文献   

3.
Rare earth ions (Eu3+ and Dy3+)-doped Gd2(WO4)3 phosphor films were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting powders and films. The results of XRD indicate that the films begin to crystallize at 600°C and the crystallinity increases with the elevation of annealing temperatures. The film is uniform and crack-free, mainly consists of closely packed fine particles with an average grain size of 80 nm. Owing to an energy transfer from WO42− groups, the rare earth ions show their characteristic emissions in crystalline Gd2(WO4)3 phosphor films, i.e., (J=0, 1, 2, 3; J′=0, 1, 2, 3, 4, not in all cases) transitions for Eu3+ and (J=13/2, 15/2) transitions for Dy3+, with the hypersensitive transitions (Eu3+) and (Dy3+) being the most prominent groups, respectively. Both the lifetimes and PL intensity of the Eu3+ () and Dy3+ () increase with increasing the annealing temperature from 500°C to 800°C, and the optimum doping concentrations for Eu3+ and Dy3+ are determined to be 30 and 6 at% of Gd3+ in Gd2(WO4)3 film host lattices, respectively.  相似文献   

4.
TiO2 thin film photocatalysts coated onto soda lime glass were prepared by a dip coating process using a highly viscous solvent. The source of the TiO2 was tetraisopropyl orthotitanate, and -terpineol was used as the solvent. Two types of thin film preparation procedures based on dip coating (a sol-gel system and thermal decomposition system) were used to prepare the samples. TiO2 thin films were obtained after calcination at 450°C for 1 hour. The film thickness obtained with a single dipping was proportional to the viscosity of the dip coating solutions. The obtained thin films were transparent with a thickness of 1 m. The crystal form of the obtained photocatalyst films was anatase alone. The thin films were formed with aggregated nano-sized TiO2 single crystals (7–15 nm). The photocatalytic activity of the TiO2 thin films, as evaluated by the photooxidation of NO (1 ppm) in dry air, was as high as our previous TiO2 thin films prepared by the sol-gel method.  相似文献   

5.
C60-polysiloxane hybrids were prepared by the reaction of triethoxysilylated C60 (TES-C60) with methylpolysiloxane (MPS) or , -dihydroxypolydimethylsiloxane (STPDS). TES-C60 was synthesized by hydrosilylation using triethoxysilane and C60 in the presence of chloroplatinic acid. TES-C60 was mixed with MPS and heated to provide a bulk body of C60 containing polysiloxane hybrid in a Si/C60 molar ratio of 1000:500. The formation of this hybrid is based on the hydrolytic polycondensation of TES-C60 and MPS to fix C60 into the silica matrix by a chemical bond. TES-C60 and STPDS also provide an isolatable thin film of C60 containing polysiloxane hybrid by an ethanol-forming condensation reaction. Because no gelation was observed when only STPDS was aged, it is thought that TES-C60 serves as a cross-linking point in gel formation.  相似文献   

6.
Na Zheng  Zhuobin Yuan 《Talanta》2009,79(3):780-786
Magnetic nanoparticles (Fe3O4) were synthesized by a chemical coprecipitation method. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to confirm the crystallite structure and the particle's radius. The Fe3O4 nanoparticles and chitosan (CS) were mixed to form a matrix in which haemoglobin (Hb) can be immobilized for the fabrication of H2O2 biosensor. The Fe3O4-CS-Hb film exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks due to the redox of Hb-heme Fe (III)/Fe (II) in a pH 7.0 phosphate buffer. The formal potential of Hb-heme Fe(III)/Fe(II) couple varied linearly with the increase of pH in the range of 4.0-10.0 with a slope of 46.5 mV pH−1, indicating that electron transfer was accompanied with single proton transportation in the electrochemical reaction. The surface coverage of Hb immobilized on Fe3O4-CS film glassy carbon electrode was about 1.13 × 10−10 mol cm−2. The heterogeneous electron transfer rate constant (ks) was 1.04 s−1, indicating great facilitation of the electron transfer between Hb and magnetic nanoparticles-chitosan modified electrode. The modified electrode showed excellent electrocatalytic activity toward oxygen and hydrogen peroxide reduction. The apparent Michaelis-Menten constant for H2O2 was estimated to be 38.1 μmol L−1.  相似文献   

7.
Porous SiO2 films were successfully deposited on silicon substrates by a modified base-catalyzed Sol-Gel process (MBCP) containing polyvinyl alcohol (PVA). The process conditions, such as the gelation time, the synthesis temperature, the stabilizing agent of the precursor solution and the spin coating speed, the heat-treatment, the annealing temperature of the film on the microstructure and porosity of porous SiO2 films were systematically investigated by SEM, XRD and ellipsometry techniques. This study provides a novel preparation technique for the porous SiO2 film. Using this process, the resultant film can reach a thickness of 3.6 m for one layer, a porosity of 25–50%, a low thermal conductivity of 0.11 W/m·K. This film will be used as a low dielectric layer, an thermal-insulating layer and a low refractive index layer.  相似文献   

8.
Highly (110)-oriented Ba0.65Sr0.35TiO3 films were deposited on Pt/LaNiO3/SiO2/Si substrates by a sol–gel method. It was found that the (110)-preferred Pt film was very effective for growing (110)-oriented ferroelectric films with perovskite structure. The as-grown Ba0.65Sr0.35TiO3 films showed good dielectric properties with dielectric constant and loss tangent tan δ = 0.026. Excellent dielectric tunability was also achieved in the (110)-oriented films. With applying an electric field of 230 kV/cm at 100 kHz, the dielectric tunability and the figure of merit can reach up to 63.4% and 16, respectively. These results indicate that the highly (110)-oriented Ba0.65Sr0.35TiO3 film is a promising candidate for the applications in microwave tunable devices.  相似文献   

9.
Calcium modified lead titanate sol was synthesized using a soft solution processing, the so-called polymeric precursor method. In soft chemistry method, soluble precursors such as lead acetate trihydrate, calcium carbonate and titanium isopropoxide, as starting materials, were mixed in aqueous solution. Pb0.7Ca0.3TiO3 thin films were deposited on platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure, dielectric and optical properties of the thin films were investigated. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 299 and 0.065, respectively, for a thin film with 230 nm thickness annealed at 600°C for 2 h. The remanent polarization (2Pr) and coercive field (E c) were 32 C/cm2 and 100 kV/cm, respectively. Transmission spectra were recorded and from them, refractive index, extinction coefficient, and band gap energy were calculated. Thin films exhibited good optical transmissivity, and had optical direct transitions. The present study confirms the validity of the DiDomenico model for the interband transition, with a single electronic oscillator at 6.858 eV. The optical dispersion behavior of PCT thin film was found to fit well the Sellmeir dispersion equation. The band gap energy of the thin film, annealed at 600°C, was 3.56 eV. The results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of PCT thin films.  相似文献   

10.
A novel nano-TiO2 polymer modified glassy carbon (GC) electrode was developed for the determination of an organophosphorous pesticide, fenitrothion (-NO2), in citrate buffer solution. The electrochemical behavior of fenitrothion was characterized by using cyclic voltammetry. An irreversible form, -NO2, was transformed into a reversible redox couple (-NHOH/-NO), and it can be used to determine trace fenitrothion by square wave voltammetry. The experimental parameters, such as film thickness, pH value, accumulation potential and time were optimized. Interestingly, a cyclic voltammetric scan was observed to be more effective than a constant potential for the accumulation of fenitrothion. A linear response over a fenitrothion concentration of 2.5×10–8 to 1.0×10–5M was exhibited, with a detection limit of 1.0×10–8M (S/N=3). The high sensitivity and selectivity of this film electrode was demonstrated by its practical application to the determination of trace amounts of fenitrothion in lake water and apple samples.  相似文献   

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