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1.
Composition modulated Bi2(Te1−xSex)3 thin films were prepared on stainless steel substrates by cathodic electrodeposition. The composition was dependent on the deposition conditions. It was possible to obtain, in the same electrolyte, films with either an excess or a deficiency of bismuth in relation to stoichiometric Bi2(Te0.9Se0.1)3 by changing the deposition potential or the applied current density. The excess of bismuth was reached at the highest cathodic conditions. The variation of the crystallographic axis and the morphology with a granular structure were correlated with the presence of the Bi enrichment in the ternary. The crystallographic texture of bismuth telluride films was studied according to the electrodeposition conditions. The films presented a fibre texture, and a main orientation {11.0} was observed. Electrical and thermoelectric properties of a Bi1.98Te2.67Se0.39 film were measured and showed an n-type behaviour.  相似文献   

2.
Ferroelectric thin films of Nd and Mn co-doped bismuth titanate, Bi3.15Nd0.85Ti3−x Mn x O12 (BNTM) (x = 0–0.1), were fabricated on Pt/TiO2/SiO2/Si(100) substrates by a sol–gel technique. The BNTM films had a polycrystalline perovskite structure and uniform and dense surface morphologies. A lattice distortion was observed in the BNTM films due to Mn ion doping. The ferroelectric measurement of the films indicated that the values of coercive field (E c ) decreased gradually with the increase of the Mn content (x), however, the remanent polarization (P r ) increase firstly and then decrease with the increase of x. The sample with x = 0.05 had optimum electrical properties and a maximum 2P r value. The 2P r and 2E c values of the film at a maximum applied electric field of 400 kV/cm were 38.3 μC/cm2 and 180 kV/cm, respectively. Moreover, this BNTM capacitors did not show fatigue behaviors after 1.0 × 1010 switching cycles at a frequency of 1 MHz, suggesting a fatigue-free character. The main reason for the increase of the 2P r and the decrease of the 2E c might be attributed to the lattice distortion in BNTM films due to Mn ion doping.  相似文献   

3.
Ca3Co4O9 powder was prepared by a polyacrylamide gel route in this paper. The effect of the processing on microstructure and thermoelectric properties of Ca3Co4O9 ceramics via spark plasma sintering were investigated. Electrical measurement shows that the Seebeck coefficient and conductivity are 170 μV/K and 128 S/cm, respectively, at 700 °C, yielding a power factor value of 3.70 × 10−4 W m−1 K−2 at 700 °C, which is larger than that of Ca3Co4O9 ceramics via solid-state reaction processing. The polyacrylamide gel processing is a fast, cheap, reproducible and easily scaled up chemical route to improve the thermoelectric properties of Ca3Co4O9 ceramics by preparing the homogeneous and pure Ca3Co4O9 phase.  相似文献   

4.
We have measured the second acid dissociation constant, K 2a , at several ionic strengths for hydrogen telluride (H2Te) using the Charge Transfer to Solvent (CTTS) uv spectra of its anions HTe and Te2−. Since it is produced in our solutions, we have also determined the spectra of Te2 2− both in the uv and in the visible regions. At 25 C, K 2a = (1.28 ± 0.02) × 10−12 by extrapolation to zero ionic strength. Its value at an ionic strength equal to 0.5 mol.dm-3 was estimated to be (8.7 ± 0.2) × 10−12. The solution thermodynamics of these species are also discussed and comparisons are made to related acids.  相似文献   

5.
The synthesis of new compounds based on Bi2O3 is investigated because they can be used as new environmentally friendly inorganic pigments. Chemical compounds of the (Bi2O3)1–x(Er2O3)x type were synthetized. The host lattice of these pigments is Bi2O3 that is doped by Er3+ ions. The incorporation of doped ions provides interesting colours and contributes to an increase in the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments.  相似文献   

6.
Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi2−xSbxTe3) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi2−xSbxTe3 matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.  相似文献   

7.
We report a novel route to the fabrication of 3D nanostructured stoichiometric bismuth telluride (Bi2Te3) films by electrodeposition through inverse lipid cubic phases as evidenced by Small-angle X-ray Scattering (SAXS) and Helium Ion Microscopy (HIM). The nanostructured Bi2Te3 films were composed of interconnected nanowires with diameters of 60–150 Å.  相似文献   

8.
In this work we report the performance of permeation barriers based on organic/inorganic multilayer stacks. We have used PMMA-SiO2 (poly methyl methacrylate-silica) hybrid films synthesized through a sol–gel route as organic–inorganic components, whereas Al2O3 thin films were used as the inorganic component. The hybrid layers were deposited by dip coating and the Al2O3 by atomic layer deposition (ALD), films were prepared on polyethylene naphthalene (PEN) substrates. The permeability of the films and stacks is evaluated using helium as the diffusion gas in a custom made ultra-high vacuum system. The results show that permeability for PEN is reduced from 5 × 10−3 g/m2-day to about 9 × 10−5 g/m2-day for the best multiple barrier evaluated. Increased barrier properties are due to the increasing in the path and hence the lag-time of the permeating gas. In particular, we report the surface roughness of the different layers and its impact on the barrier performance. The hybrid layers reduced notably the roughness of the bare PEN substrate improving the quality of the Al2O3 layer in the barrier. The optical transmittance of the barriers in the visible region is higher than 80% in all the studied cases.  相似文献   

9.
Preliminary examinations regarding formation of bismuth titanates in a part of Bi2O3—TiO2 system rich with TiO2 have been carried out. Bismuth titanates have been synthesized from mixtures of Bi2O3 and TiO2 (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi4Ti3O12, Bi2Ti2O7 and Bi2Ti4O11. Existence of controversial bismuth titanate of formula Bi2Ti3O9 in the Bi2O3—TiO2 system has not been confirmed.  相似文献   

10.
The heat capacity and the heat content of bismuth niobate BiNb5O14 were measured by the relaxation time method, DSC and drop method, respectively. The temperature dependence of heat capacity in the form C pm=455.84+0.06016T–7.7342·106/T 2 (J K–1 mol–1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S m=397.17 J K–1 mol–1 was derived from the low temperature heat capacity measurement.  相似文献   

11.
The EMF method with a solid Cu+-conducting electrolyte of Cu4RbCl3I2 was sued to study the Cu-Tl-Te system in the temperature range of 300–420 K. A diagram of solid-phase equilibriums of this system is constructed, partial molar functions of copper in alloys, standard thermodynamic functions of formation and standard entropies of CuTlTe2, CuTl4Te3, Cu2TlTe2, Cu3TlTe2, Cu9TlTe5 triple compounds and Cu x Tl5 − x Te3 solid solutions (0 < x < 1) are calculated. The obtained results confirmed the assumption as to the possibility of using this modification for the EMF technique for thermodynamic studies of copper-containing triple systems, even if they contain a less noble component than copper.  相似文献   

12.
Lanthanum-modified bismuth titanate (Bi3.25La0.75Ti3O12, BLTO) powders were prepared by the complex polymerization method. The structure and morphology of BLTO powders were investigated by X-ray diffraction and scanning electron microscopy. The complexation of citric acid with the metallic cations was detected by Fourier transformed infrared (FT-IR). The thermal analyses of obtained gels were investigated by differential thermal gravimetric (DTG). The pure and normally stoichiometric phase of BLTO powders could be obtained at relatively low temperature of 550–700 °C even if the bismuth content is not excess in the starting precursors, while the secondary phase could be detected at lower and higher calcination temperatures. The shape of the BLTO grains is similarly to platelet in Bi-layer structure and stoichiometry BLTO was detected by the analysis of energy dispersive spectrometry.  相似文献   

13.
TiO2–SiO2 composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO2–SiO2 composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO2–SiO2) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO2–SiO2 composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO2–SiO2 composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO2–SiO2 core surface via surface functionalized reaction. The particle size of TiO2–SiO2 composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO2–SiO2 composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO2–SiO2 composite nanoparticles are well dispersed in the PU matrix.  相似文献   

14.
Electrical conductivity in the monoclinic Li2TiO3, cubic Li1.33Ti1.67O4, and in their mixture has been studied by impedance spectroscopy in the temperature range 20–730 °C. Li2TiO3 shows low lithium ion conductivity, σ300≈10–6 S/cm at 300 °C, whereas Li1.33Ti1.67O4 has 3×10–8 at 20 °C and 3×10–4 S/cm at 300 °C. Structural properties are used to discuss the observed conductivity features. The conductivity dependences on temperature in the coordinates of 1000/T versus logeT) are not linear, as the conductivity mechanism changes. Extrinsic and intrinsic conductivity regions are observed. The change in the conductivity mechanism in Li2TiO3 at around 500–600 °C is observed and considered as an effect of the first-order phase transition, not reported before. Formation of solid solutions of Li2– x Ti1+ x O3 above 900 °C significantly increases the conductivity. Irradiation by high-energy (5 MeV) electrons causes defects and the conductivity in Li2TiO3 increases exponentially. A dose of 144 MGy yields an increase in conductivity of about 100 times at room temperature. Electronic Publication  相似文献   

15.
Electrochromic titanium oxide (TiO2) films were deposited on ITO/glass substrates by chemical solution deposition (CSD). The stock solutions were spin-coated onto substrates and then heated at various temperatures (200–500 °C) in various oxygen concentrations (0–80%) for 10 min. The effects of the processing parameters on the electrochromic properties of TiO2 films were investigated. X-ray diffraction measurements demonstrated that the amorphous TiO2 films were crystallized to form anatase films above 400 °C. The electrochromic properties and transmittance of TiO2 films were measured in 1 M LiClO4–propylene carbonate (PC) non-aqueous electrolyte. An amorphous 350 nm-thick TiO2 film that was heated at 300°C in 60% ambient oxygen exhibited the maximum transmittance variation (ΔT%), 14.2%, between the bleached state and the colored state, with a ΔOD of 0.087, Q of 10.9 mC/cm2, η of 7.98 cm2/C and x in Li x ClO4 of 0.076 at a wavelength (λ) of 550 nm.  相似文献   

16.
The metal-ferroelectric-semiconductor (MFS) heterostructure has been fabricated using Bi3.25La0.75Ti3O12 (BLT) as a ferroelectric layer by sol-gel processing. The effect of annealing temperature on phase formation and electrical characteristics of Ag/BLT/p-Si heterostructure were investigated. The BLT thin films annealed at from 500°C to 650°C are polycrystalline, with no pyrochlore or other second phases. The C-V curves of Ag/BLT/p-Si heterostructure annealed at 600°C show a clockwise C-V ferroelectric hysteresis loops and obtain good electrical properties with low current density of below 2×10−8 A/cm2 within ±4 V, a memory window of over 0.7 V for a thickness of 400 nm BLT films. The memory window enlarges and the current density reduces with the increase of annealing temperature, but a annealing temperature over 600°C is disadvantageous for good electrical properties.  相似文献   

17.
The reaction of Bi2O3 + Fe2O3 mixtures with chlorine and SO2 at 250–700°C is studied. At 300–500°C, the degree of bismuth chloride sublimation from the oxide mixture increases in the presence of SO2. Chemical sublimation of FeCl3 occurs after BiCl3 is virtually completely recovered from the solid phase.  相似文献   

18.
Ni0.5Zn0.5Fe2O4 nanofibers with addition of 0–5 wt% Bi2O3 were synthesized by calcination of the electrospun polyvinylpyrrolidone/inorganic composite nanofibers at the temperature below the melting point of Bi2O3. The effects of Bi2O3 addition on the phase structure, morphology and magnetic properties of the nanofibers were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, selected area electron diffraction and vibrating sample magnetometer. It is found that the nanofiber diameter, crystallite size and magnetic parameters can be effectively tuned by simply adjusting the amount of Bi2O3 addition. The average diameter of Ni0.5Zn0.5Fe2O4 nanofibers doped with different contents of Bi2O3 ranges from 40 to 63 nm and gradually decreases with increasing Bi2O3 content. The addition of Bi2O3 does not induce the phase change and all the samples are a single-phase spinel structure. The amorphous Bi2O3 tends to concentrate on the nanoparticle surface and/or grain boundary and can retard the particles motion as well as the grain growth, resulting in a considerable reduction in grain size compared to the pristine sample. The specific saturation magnetization and coercivity of the nanofibers gradually decrease with the increase of Bi2O3 amount. Such behaviors are explained on the basis of chemical composition, surface effect, domain structure and crystal anisotropy.  相似文献   

19.
Mechanism by which nanocrystalline Bi4Ti3O12 is formed in thermal treatment of coprecipitated hydroxides was studied. It was shown that the onset of the active formation is correlated with the melting point of the surface phase based on bismuth oxide. The technological synthesis parameters of Bi4Ti3O12, at which crystallite sizes in the range 35–60 nm are provided, were determined.  相似文献   

20.
A method for the synthesis of the silver(I) complex with the closo-decaborate anion and triphenylphosphine [Ag2(Ph3P)2B10H10] n was developed and the structure of this complex was studied. The polymeric chain of the complex is formed with participation of Ag(I) atoms, which coordinate the B10H102− anions through the apical (B(1)–B(2), B(9)–B(10)) and equatorial (B(3)–B(6), B(5)–B(8)) edges, the metalligand bonding occurring through three-center two-electron bonds (MHB). The P atoms of two triphenylphosphine molecules are also incorporated in the inner coordination sphere of the metal: the CN of the silver atom is 4 + 1.  相似文献   

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