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1.
Mesoporous TiO2 powders were prepared in 1 min from an aqueous mixture of chelated complex titanium precursor and tri-block copolymer by using a process combining evaporation induced self-assembly (EISA) and spray pyrolysis. Photocatalytic activity was evaluated by measuring the rate of hydrogen evolution from methanol solution. The prepared powders were mainly anatase phase and had worm-like pores. Crystallite size was in the range from 7.8 to 18.6 nm in diameter. The mesoporous TiO2 powders calcined at 823 K had surface area of 144 m2 g−1 and high pore volume of 0.33 cm3 g−1. Pore size distribution was also narrow. In addition, it had high light absorption intensity below 350 nm. The rate of hydrogen evolution was by a factor of six higher than the rate measured with commercial nano-sized TiO2 powder (Degussa P-25). Unique structural and optical properties, which were mainly originated from our new combined process of EISA and spray pyrolysis, contributed to the enhanced rate of hydrogen evolution. 相似文献
2.
A combustion process was used to synthesize crystalline powders of La-substituted barium chromium hexaferrites Ba1 − xLaxFe11.5Cr0.5O19 (x = 0-0.25). The structures, morphologies and ferromagnetic properties of La3+ substituted nanocomposites were characterized by powder X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). XRD results showed that single-phase barium chromium ferrite powders was found at La content x ≤ 0.2. From the SEM, it was observed that the particles calcined at 1100 °C had a plate-like hexagonal shape. The results of magnetic mensuration revealed that both MS and HC of barium hexaferrite increased up to x = 0.1, and then decreased with the increasing of La content. 相似文献
3.
Polycrystalline α-AgGaO2 powders were prepared by the hydrothermal conversion of β-AgGaO2. The β-AgGaO2 was synthesized by the ion exchange reaction between NaGaO2 and molten AgNO3 under nitrogen atmosphere. The α-AgGaO2 thus synthesized was used as the target for pulsed laser ablation. The films grown on α-Al2O3 (0001) single crystal substrates are crystalline and are 50% transparent in the visible region. The temperature dependence of conductivity shows a semiconducting behaviour with room temperature conductivity 3 × 10− 4 Scm− 1. The positive sign of Seebeck coefficient (+ 70 μVK− 1) demonstrated the p-type conduction in the films. Transparent p-n heterojunctions on a glass substrate were fabricated. The structure of the device was glass/ITO/n-ZnO/p-AgGaO2. The ratio of forward to reverse current was more than 100 in the range of − 1.5 V to + 1.5 V. 相似文献
4.
The electrical, structural, and optical characteristics of Ag/ZnO-doped In2O3 (IZO) ohmic contacts to p-type GaN:Mg (2.5 × 1017 cm− 3) were investigated. The Ag and IZO (10 nm/50 nm) layers were prepared by thermal evaporation and linear facing target sputtering, respectively. Although the as-deposited and 400 °C annealed samples showed rectifying behavior, the 500 and 600 °C annealed samples showed linear I-V characteristics indicative of the formation of an ohmic contact. The annealing of the contact at 600 °C for 3 min in a vacuum (~ 10− 3 Torr) resulted in the lowest specific contact resistivity of 1.8 × 10− 4 Ω·cm2 and high transparency of 78% at a wavelength of 470 nm. Using Auger electron spectroscopy, depth profiling and synchrotron X-ray scattering analysis, we suggested a possible mechanism to explain the annealing dependence of the electrical properties of the Ag/IZO contacts. 相似文献
5.
Single-crystal PbxLa1 − xTiO3 (PLT) nanorods of various La concentrations have been synthesized by polymer-assisted hydrothermal method. The nanorods have diameters of 25-60 nm and average lengths of 3 μm. With tetragonal lattices structures, the PLT nanorods grow along the (001) direction. As La concentration increasing, the tetragonality c/a decreases and the Raman mode E(1TO) becomes softening. PLT nanorods with various lengths and diameters have been prepared by using different polymer additives. To fabricate well-crystallized nanorods, an annealing process after the hydrothermal treatment is proved to be necessary. 相似文献
6.
Su-E Hao Chun-Yan Wang Dong-Sheng Fu Ju-Sheng Zhang Yuan Wei Wei-Li Wang 《Thin solid films》2010,518(20):5645-3301
Ba(1 − x)SrxTiO3 powders with different Ba/Sr ratios (x = 0.10, 0.25, 0.40, 0.55, 0.70) and La-doped Ba0.9Sr0.1TiO3·yLa powders (y = 0.002, 0.004, 0.006, 0.008, 0.010) have been prepared by sol-gel technology using dehydrated barium-acetate, strontium-carbonate, lanthanum-nitrate, and titanium-isopropoxide as raw materials. The experimental results show that the dielectric properties of Ba(1 − x)SrxTiO3 powders depend on the Ba/Sr ratios. When the Sr fraction is 0.10, the dielectric constant is relatively higher and the dielectric loss is relatively lower, which are more than 2000 and less than 2.0 × 10− 2 at 1000 Hz, respectively, the most important is that this kind of powder has better frequency stability. La-doping can increase the dielectric constant distinctly, but the dielectric loss can also be increased. Their dielectric properties at 1.0 × 103 Hz are better than those at 1.0 × 105 Hz. At 1.0 × 103 Hz the dielectric constant is much higher, while the dielectric loss is much lower. The dielectric constant of different La-doping contents is nearly 3.5 × 104 and the dielectric loss is less than 0.20 when La fraction is 0.008. The La-doped BST sample also has better frequency stability, especially at high frequency. La-doped BST thin films are successfully deposited on mild steel substrates by using plasma spray system with suspension precursors of Ba0.90Sr0.10TiO3·0.8La powders. The XRD patterns of Ba0.90Sr0.10TiO3 and Ba0.90Sr0.10TiO3·0.8La powders are almost the same. No new peaks appear after La-doping, but the peaks move slightly to a larger degree, which indicates that the element La has entered the lattice of the Ba0.90Sr0.10TiO3 and has made the constant of the crystal cell reduce. The XRD pattern of the thin films is just like that of the Ba0.90Sr0.10TiO3·0.8La powders except a peak corresponding to Fe substrate. The SEM results show that the thin films have a uniform and smooth surface. The morphology of cross-section shows a columnar grain structure indicating smooth surface and uniform thickness of the film. The thickness of the film is about 15 um. The thin films obtained are expected to be prospective material for applications in tunable microwave devices. 相似文献
7.
K. Timmo M. Altosaar J. Raudoja E. Mellikov T. Varema M. Danilson M. Grossberg 《Thin solid films》2007,515(15):5887-5890
The effect of sodium doping to the electrical and photoluminescence properties of CuInSe2 monograin powders was studied. Sodium was added in controlled amounts from 5 × 1016 cm− 3 to 1 × 1020 cm− 3. The photoluminescence spectra of Na-doped stoichiometric CuInSe2 powders had two bands with peak positions at 0.97 and 0.99 eV. The photoluminescence bands showed the shift of peak positions depending on the Na doping level. Peak positions with maximum energy were observed if added sodium concentration was 1 × 1019 cm− 3. This material had the highest carrier concentration 2 × 1017 cm− 3. In the case of stoichiometric CuInSe2 (Cu:In:Se = 25.7:25.3:49.0), Na doping at concentrations of 3 × 1017 cm− 3 and higher avoided the precipitation of Cu-Se phase. Solar cells output parameters were dependent on the Na doping level. Sodium concentration 3 × 1018 cm− 3 resulted in the best open-circuit voltage. 相似文献
8.
Muxina Konarova 《Materials Research Bulletin》2008,43(12):3305-3317
LiFePO4 powders could be successfully prepared from a precursor solution, which was composed of Li(HCOO)·H2O, FeCl2·4H2O and H3PO4 stoichiometrically dissolved in distilled water, by ultrasonic spray pyrolysis at 500 °C followed by heat treatment at sintering temperatures ranging from 500 to 800 °C in N2 + 3% H2 gas atmosphere. Raman spectroscopy revealed that α-Fe2O3 thin layers were formed on the surface of as-prepared LiFePO4 powders during spray pyrolysis, and they disappeared after sintering above 600 °C. The LiFePO4 powders prepared at 500 °C and then sintered at 600 °C exhibited a first discharge capacity of 100 mAh g−1 at a 0.1 C charge-discharge rate. To improve the electrochemical properties of the LiFePO4 powders, LiFePO4/C composite powders with various amounts of citric acid added were prepared by the present method. The LiFePO4/C (1.87 wt.%) composite powders prepared at 500 °C and then sintered at 800 °C exhibited first-discharge capacities of 140 mAh g−1 at 0.1 C and 84 mAh g−1 at 5 C with excellent cycle performance. In this study, the optimum amount of carbon for the LiFePO4/C composite powders was 1.87 wt.%. From the cyclic voltammetry (CV) and AC impedance spectroscopy measurements, the effects of carbon addition on the electrochemical properties of LiFePO4 powders were also discussed. 相似文献
9.
LiFePO4/C composite with carbon core structure was successfully prepared by using araldite as carbon source. The microstructure and morphology of LiFePO4/C composite were confirmed by X-ray diffraction and transmission electron microscopic observation. The experimental results show that this structure is entirely different from carbon coating. The LiFePO4/C composite forms a common core structure in which carbon is used as line core and carbon core is covered by nano-LiFePO4 grains. Moreover, the LiFePO4/C composite exhibits higher tap density of 1.66 g cm− 3, shows higher capacity about 162 mAhg− 1 applied 30 mAg− 1 current, excellent cyclic ability and rate capability about 139 mAhg− 1 applied 700 mAg− 1 current at room temperature. 相似文献
10.
Manganese oxide/carbon composite materials were prepared by introducing the carbon powders into the potentiodynamical anodic co-deposited manganese oxide in 0.5 mol L− 1 MnSO4 and 0.5 mol L− 1 H2SO4 mixed solution at 40 °C. The surface morphology and structure of the composite material were examined by scanning electron microscope and X-ray diffraction. Cyclic voltammetry tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of manganese oxide and carbon. These composite materials with rough surface, which consisted of approximately amorphous manganese oxide, were confirmed to possess the ideal capacitive property. The highest specific capacitance of manganese oxide/carbon composite electrode was up to 410 F g− 1 in 1.0 mol L− 1 Na2SO4 electrolyte at the scan rate 10 mV s− 1. The synthesized composite materials exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors. 相似文献
11.
Matthieu Y. Versavel 《Thin solid films》2007,515(18):7171-7176
Smooth and compact thin films of amorphous and crystalline antimony sulfide (Sb2S3) were prepared by radio frequency sputtering of an Sb2S3 target. As-deposited films are amorphous. Polycrystalline antimony sulfide films composed of ∼ 500 nm grains are obtained by annealing the as-deposited films at 400 °C in sulfur vapors. Both amorphous and crystalline antimony sulfide have strong absorption coefficients of 1.8 × 105 cm− 1 at 450 nm and 7.5 × 104 cm− 1 at 550 nm, and have direct bandgaps with band energies of 2.24 eV and 1.73 eV, respectively. These results suggest the potential use of both amorphous and crystalline antimony sulfide films in various solid state devices. 相似文献
12.
Porous layers were prepared from DEGUSSA's ITO (In2O3:Sn) nanoparticle dispersion by doctor blading followed by annealing in air. We investigated the influence of various annealing parameters on electrical, optical and morphological thin film properties.Conductance rises with increasing annealing temperature and time by more than three orders of magnitude up to 44 Ω− 1cm− 1. Besides this we found an abrupt decrease in free charge carrier concentration above a critical annealing temperature of 250 °C, which leads to a step in conductance curve. In spite of particle growing during annealing no decrease in porosity was observed and in opposite to compact material, nanoparticle layers do not exhibit an appreciable shrinkage below recrystallisation temperature. These both indicate a densification hindering particle pinning effect, which is believed to be currently the main obstruction to achieve higher electrical conductivities. 相似文献
13.
Photocatalytically active indium tin oxide thin film electrodes were prepared by electron beam evaporation technique onto a glass substrate having thickness 120 nm. Degradation of reactive dye yellow direct 42 has been performed using photoeletrocatalysis. A biased potential is applied across indium tin oxide photoelectrode illuminated by UV light. The best experimental conditions were found to be dye concentration 1.0 × 10− 5 mol L− 1, pH 5.25 and 0.5 mol L− 1 NaCl as supporting electrolyte when the photoelectrode was biased at + 0.5 V versus saturated calomel electrode. The effects of other electrolytes, dye concentration, pH solution, electrode annealing temperature and applied potentials have been also investigated and are discussed. Several common inorganic salts Na2SO4, Na2CO3, NaNO3 and NaCl were chosen to act as supporting electrolytes, which was added into the dye solution. It is shown that the charge-transfer resistance of photoanode can be calculated by the analysis of its electrochemical impedance spectroscopy, and the photoelectrocatalytic degradation rate of yellow direct 42 was inversely proportional to the value of charge-transfer resistance of photoelectrodes at different pH. The value of charge-transfer resistance is smaller, the higher its photoelectro-activity is. 相似文献
14.
Copper indium disulphide CuInS2 (CIS) and diselenide CuInSe2 (CISe) and their alloys with gallium CuIn1 − xGaxSe2 (CIGSe) thin films have been prepared using both high- and non-vacuum processes. The well known two-stage process consisting in a sequential sputtering of Cu and In thin layers and a subsequent sulfurisation has led to the formation of good quality CuInS2 ternary compound. The films exhibit the well known chalcopyrite structure with a preferential orientation in the (112) plane suitable for the production of the efficient solar cells. The absorption coefficient of the films is higher than 104 cm− 1 and the band gap value is about 1.43 eV. A non-vacuum technique was also used. It consists on a one step electrodeposition of Cu, In and Se and in a second time Cu, In, Se and Ga. From the morphological and structural point of view, the films obtained are similar to those prepared by the first technique. The band gap value increases up from 1 eV for the CIS films to 1.26 eV for the CuIn1 − xGaxSe2 with 0 < x < 0.23. The resistivity at room temperature of the films was adjusted to 10 Ωcm after annealing. The films exhibit an absorption coefficient more than 105 cm− 1. The most important conclusion of this study is the interesting potential of electrodeposition as a promising option in low-cost CISe and CIGSe thin film based solar cells processing. 相似文献
15.
We have investigated the electrical, optical, structural, and annealing properties of indium zinc tin oxide (IZTO) films prepared by an unbalanced radio frequency (RF) magnetron sputtering at room temperature, in a pure Ar ambient environment. It was found that the electrical and optical properties of unbalanced RF sputter grown IZTO films at room temperature were influenced by RF power and working pressure. At optimized growth condition, we could obtain the IZTO film with the low resistivity of 3.77 × 10− 4 Ω cm, high transparency of ~ 87% and figure of merit value of 21.2 × 10− 3Ω− 1, without the post annealing process, even though it was completely an amorphous structure due to low substrate temperature. In addition, the field emission scanning electron microscope analysis results showed that all IZTO films are amorphous structures with very smooth surfaces regardless of the RF power and working pressure. However, the rapid thermal annealing process above the temperature of 400 °C lead to an abrupt increase in resistivity and sheet resistance due to the transition of film structure from amorphous to crystalline, which was confirmed by X-ray diffraction examination. 相似文献
16.
Zinc oxide films on a single crystal Mo(100) substrate were fabricated by annealing the pre-deposited metal Zn films in 10− 5-10− 4 Pa O2 ambience at 300-525 K, and were characterized by in situ Auger electron spectroscopy, electron energy loss spectroscopy, low energy electron diffraction and high-resolution electron energy loss spectroscopy. The results show that the atomic ratio of oxygen to zinc in zinc oxide film is significantly dependent on sample annealing temperature and O2 pressure. A stoichiometric zinc oxide film has been obtained under ∼10− 4 Pa O2 at about 400 K. A redshift of Fuchs-Kliewer phonon energy correlated with surface oxygen deficiency is observed. 相似文献
17.
Zinc nitride thin films were deposited by magnetron sputtering using ZnN target in plasma containing either N2 or Ar gases. The rf-power was 100 W and the pressure was 5 mTorr. The properties of the films were examined with thermal treatments up to 550 °C in N2 and O2 environments. Films deposited in Ar plasma were opaque and conductive (ρ ∼ 10− 1 to 10− 2 Ω cm, ND ∼ 1018 to 1020 cm− 3) due to excess of Zn in the structure. After annealing at 400 °C, the films became more stoichiometric, Zn3N2, and transparent, but further annealing up to 550 °C deteriorated the electrical properties. Films deposited in N2 plasma were transparent but very resistive even after annealing. Both types of films were converted into p-type ZnO upon oxidation at 400 °C. All thermally treated zinc nitride films exhibited a shoulder in transmittance at around 345 nm which was more profound for the Ar-deposited films and particularly for the oxidized films. Zinc nitride has been found to be a wide band gap material which makes it a potential candidate for transparent optoelectronic devices. 相似文献
18.
Y3 − xCexAl5O12 (YAG:Ce3+) phosphor powders were successfully prepared by hydrothermal-homogenous precipitation (HHP) method, under mild conditions with inexpensive aluminum and yttrium nitrates as the starting materials and urea as homogenous precipitant. The pure YAG crystalline phase could be formed after hydrothermal treatment at 100 °C for 4 h and 240 °C for 20 h and postannealing process at 1200 °C for 2 h. All of the as-prepared YAG:Ce3+ powders did not have the CeO2 phase. The photoluminescence spectrum of crystalline YAG:Ce3+ phosphors showed the emission intensity of phosphor increased with increasing the annealed temperature and reached its maximum as the molar fraction of cerium ion was 0.10, and also showed the maximum emission wavelength nearly unchanged with the calcination temperature and cerium doping concentration. 相似文献
19.
The cathode material, LiNi0.9Co0.1O2 was prepared using a rheological phase reaction method with LiOH·H2O, home-made Ni(OH)2, and Co2O3 as starting materials. At first, the mixture of reactants and a proper amount of water reacted to form a rheological precursor. Then the dried precursor was heated at 730 °C in one step to yield the product. The effects of calcination time (between 0.5 and 10 h) on the structural, morphological and electrochemical properties were investigated. All obtained powders show a single phase with α-NaFeO2 structure (R-3m space group). The sample prepared in 2.5 h delivers the largest initial discharge capacity of 218 mA h g− 1 (3.0-4.35 V, 25 mA g− 1) and still remains 192 mA h g− 1 after 15 cycles. The method is simple, economical and effective and is promising for practical application. 相似文献
20.
Indium tin oxide (ITO) films were deposited on glass substrates by rf magnetron sputtering using a ceramic target (In2O3-SnO2, 90-10 wt%) without extra heating. The post annealing was done in air and in vacuum, respectively. The effects of annealing on the structure, surface morphology, optical and electrical properties of the ITO films were studied. The results show that the increase of the annealing temperature improves the crystallinity of the films, increases the surface roughness, and improves the optical and electrical properties. The transmittance of the films in visible region is increased over 90% after the annealing process in air or in vacuum. The resistivity of the films deposited is about 8.125×10−4 Ω cm and falls down to 2.34×10−4 Ω cm as the annealing temperature is increased to 500°C in vacuum. Compared with the results of the ITO films annealed in air, the properties of the films annealed in vacuum is better. 相似文献