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1.
Ta100-x B x alloy films were prepared by r.f.-sputtering in the chemical composition range 45 x 77. Ta100-x B x (45 x 58) films consist of the amorphous phase, while the TaB2 crystal phase was observed in Ta100-x B x (66 x 77) films. A remarkable preferred orientation with the (001) plane of TaB2 parallel to the film surface was observed in Ta34B66. The d.c. electrical conductivity of Ta100-x B x (45 x 77) films decreases with increasing boron content in the range 6.7 × 103 to 1.3 × 103–1 cm–1. The micro-Vickers hardness of Ta100-x B x (45 x 77) films was in the range 2200 to 2600 kg mm–2.  相似文献   

2.
Bi4Ti3−xNbxO12 ferroelectric thin films were fabricated on p-Si substrates by magnetron sputtering. The effects of Nb doping on microstructure and properties of Bi4Ti3−xNbxO12 films were investigated. Bi4Ti3−xNbxO12 films had the same structure as Bi4Ti3O12 with smaller and more uniform grains. The dielectric and ferroelectric properties of Bi4Ti3−xNbxO12 films were improved by Nb doping. Bi4Ti3−xNbxO12 films have better dielectric and ferroelectric properties with P r = 16.5 μC/cm2, E C < 100 kV/cm, ε r > 290, low dielectric loss (<0.9%) and clockwise C–V curves with a memory window of 0.9 V when x = 0.03–0.045, while an excessive Nb doping would lead to bad dielectric and ferroelectric properties.  相似文献   

3.
Rb2 − 2x Al2 − x A x O4 (A = Nb, Ta) solid solutions have been synthesized, and their conductivity has been measured as a function of temperature and composition. The highest rubidium ion conductivity in the Rb2 − 2x Al2 − x A x O4 solid solutions is 3.16 × 10−3 S/cm at 300°C and ∼ 2 × 10−2 S/cm at 700°C. The high rubidium ion conductivity of the synthesized solid electrolytes is mainly due to the formation of rubidium vacancies when Nb5+ or Ta5+ substitutes for Al3+ and to the specific features of the crystal structure of RbAlO2.  相似文献   

4.
Novel inorganic–organic complex nanocomposites have been prepared by using exfoliated Fe x Ti1−2x Nb1+x O5 nanosheets and poly (N-octadecyl-2-ethynyl pyridinium bromide) (PNOEtPyBr) by the method of exfoliation–reflocculation. The X-ray diffraction data of the nanocomposites indicate the formation of Fe x Ti1−2x Nb1+x O5/PNOEtPyBr nanostructure with the length of basal spacing of 4.6 nm along the stacking direction of Fe x Ti1−2x Nb1+x O5nanosheet layers. The a. c. electrical conductivity of nanocomposites decreased with the value of x. This trend was correlated with the hydration behavior of the interlayer for HFe x Ti1−2x Nb1+x O5·nH2O (x = 0–0.5) which were starting compounds of nanosheets.  相似文献   

5.
Raman spectra of sodium borosilicate glasses with a wide range of Na2O/B2O3 ratios were systematically measured. Variations of the spectra with glass composition were studied to interpret the implied distribution of Na+ ions between silicate and borate units. When Na2O/B2O3 is less than 1, all Na+ ions are associated with borate units as indicated by the absence of the 1100 cm−1 band of Si-O non-bridging bond stretching. For the (1−x)Na2O · SiO2 ·xB2O3 glass withx≦0.4 the peak-height ratio of the 950 cm−1 band to the 1080 cm−1 band was used to analyse semiquantitatively the distribution of the Na+ ions between silicate and borate units. Sodium ions are divided between silicate and borate units approximately in proportion to the amount of SiO2 and B2O3 present in these glasses. Some of the high sodium content glasses were crystallized and their spectra were compared with the bulk glass spectra. The distribution of Na+ ions in the glass was quite different from their distribution after crystallization. Spectra of high silica glasses that had been heat-treated for phase separation indicated exclusion of borate units from the silica network and the formation of borate groups. For high boron content glasses, no change was observed on heat treatment. Raman bands due to borate groups seem to be little affected by their environments. Also affiliated with the Department of Geosciences.  相似文献   

6.
The crystallization behavior and magnetic properties of Fe62Co10Si15−x B18−y Nb(x + y)−5 amorphous alloys with x = 0–5 and y = 0–5 were examined. Primary crystallization temperature of Fe62Co10Si15−x B13Nb x and Fe62Co10Si10B18−y Nb y alloys increased with the addition of Nb. The primary and secondary crystallization temperatures were well separated when the Nb content is above 4 at%. The alloys with 15–18 at% B showed a distinct supercooled region. The Nb addition decreased the Curie temperature as well as room temperature saturation magnetization. The glassy-type Fe62Co10Si10B18 alloy exhibited good soft magnetic properties as well as a supercooled liquid region of 39 K. The finding of the glassy-type Fe-based alloy without Nb element exhibiting high Bs above 1.4 T is promising for future use as a soft magnetic glass material.  相似文献   

7.
The thermoelectric power and d.c electrical conductivity of x V2O5⋅40CaO⋅(60−x)P2O5 (10 ≤ x ≤ 30) glasses were measured. The Seebeck coefficient (Q) varied from +88 μ V K−1 to −93 μV K−1 as a function of V2O5 mol%. Glasses with 10 and 15 mol% V2O5 exhibited p-type conduction and glasses with 25 and 30 mol% V2O5 exhibited n-type conduction. The majority charge carrier reversal occurred at x = 20 mol% V2O5. The variation of Q was interpreted in terms of the variation in vanadium ion ratio (V5 +/V4 +). d.c electrical conduction in x V2O5⋅40CaO⋅(60−x)P2O5 (10 ≤ x ≤ 30) glasses was studied in the temperature range of 150 to 480 K. All the glass compositions exhibited a cross over from small polaron hopping (SPH) to variable range hopping (VRH) conduction mechanism. Mott parameter analysis of the low temperature data gave values for the density of states at Fermi level N (EF) between 1.7 × 1026 and 3.9 × 1026 m−3 eV−1 at 230 K and hopping distance for VRH (RVRH) between 3.8 × 10−9m to 3.4 × 10−9 m. The disorder energy was found to vary between 0.02 and 0.03 eV. N (EF) and RVRH exhibit an interesting composition dependence.  相似文献   

8.
Epitaxial (Ni, Zn)Fe2O4 films were prepared on (100) MgO single crystal substrate by lowpressure chemical vapour deposition using a thermal decomposition of acetylacetonatocomplexes, Ni(acac)2, Zn(acac)2 and Fe(acac)3. These complexes were evaporated at 157, 79 and 146° C, respectively, and transported with nitrogen carrier gas (flow rate 100 ml min−1) to the deposition furnace. Polycrystalline and epitaxial films were grown at 500 to 600 and 600 to 650° C, respectively, under a pressure of 12 torr. The epitaxial film of Ni1−xZnxFe2O4 (x⋍0.4) treated at 600° C for 60 min, showed the saturation magnetization of 67 e.m.u. g−1 and the coercive force of 20 to 30 Oe.  相似文献   

9.
We have studied the optical absorption and luminescence spectra of 45Na2O · xNb2O5 · (55 − x)P2O5 glasses containing 5, 10, 20, 25, 30, and 35 mol % Nb2O5. The results indicate that the absorption band around 26000 cm−1, responsible for the yellow color of the glasses, is due to the [Nb(5+)--O] center and disappears upon secondary heat treatment. Heat treatment of europium-doped glasses increases the concentration of Eu3+ centers in an asymmetric environment, which is accompanied by an increase in luminescence efficiency. The reason for this is that the Eu3+ ions are located outside the niobate subsystem of the glass matrix. The europium in the glasses studied acts as a protector ion.  相似文献   

10.
Glasses with composition (70 − x) B2O3·15Bi2O3·15LiF·xNb2O5 with x = 0–1.0 mol% were prepared by conventional glass-melting technique. The molar volume V m values decrease and the glass transition temperatures T g increase with increase of Nb2O5 content up to 0.2 mol%, which indicates that Nb5+ ions act as a glass former. Beyond 0.2 mol% Nb2O5 the V m increases and the T g decreases, which suggests that Nb5+ ions act as a glass modifier. The FTIR spectra suggest that Nb5+ ions are incorporated into the glass network as NbO6 octahedra, substituting BO4 groups. The temperature dependence of the dc conductivity follows the Greaves variable range hopping model below 454 K, and follows the small polaron hopping model at temperatures >454 K. σ dc, σ ac conductivity and dielectric constant (ε) decrease and activation energy for dc conduction ΔE dc which increases with increasing Nb2O5 content up to 0.2 mol%, whereas σ dc, σ ac and (ε) increase and ΔE dc decreases with increasing Nb2O5 content beyond 0.2 mol%. The impedance spectroscopy shows a single semicircle or arcs which indicate only the ionic conduction mechanism. The electric modulus formalism indicates that the conductivity relaxation is occurring at different frequencies exhibit temperature-independent dynamical process. The (FWHM) of the normalized modulus increases with increase in Nb2O5 content suggesting that the distribution of relaxation times is associated with the charge carriers Li+ or F ions in the glass network.  相似文献   

11.
Glasses of the xFe2O3·(100 − x)[B2O3·SrO] system, with 0 ≤ x ≤ 30 mol%, were studied by EPR and magnetic susceptibility measurements. EPR spectroscopy and magnetic susceptibility measurements show that the Fe3+ ions are localized in sites of distorted octahedral symmetry and in clustered formations containing both Fe3+ and Fe2+ ions. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample.  相似文献   

12.
Ba3Ti4−x (Fe1/2Nb1/2) x Nb4O21 (0 ≤ x ≤ 4) ceramics with the substitution of (Fe1/2Nb1/2) for Ti were investigated. The modified Ba3Ti4Nb4O21 dielectric ceramics prepared via the solid state reaction route exhibited single hexagonal structure. The dielectric constant and the quality factor of Ba3Ti4−x (Fe1/2Nb1/2) x Nb4O21 (0 ≤ x ≤ 4) ceramics decreased with an increase of x. Improved temperature coefficient of the resonant frequency of samples was obtained by the substitution of (Fe1/2Nb1/2) for Ti. Optimal microwave dielectric properties of ε = 50, Q × f = 5200 GHz, and τ f = 10 ppm/°C in Ba3Ti2(Fe1/2Nb1/2)2Nb4O21 were obtained, which indicated its potential for microwave application.  相似文献   

13.
The chemical vapor deposited (CVD) BP films on Si(100) (190 nm)/SiO x (370 nm)/Si(100) (625 μm) (SOI) and sapphire (R-plane) (600 μm) substrates were prepared by the thermal decomposition of the B2H6–PH3–H2 system in the temperature range of 800–1050 °C for the deposition time of 1.5 h. The BP films were epitaxially grown on the SOI substrate, but a two-step growth method, i.e., a buffer layer at lower temperature and sequent CVD process at 1000 °C for 1.5 h was effective for obtaining a smooth film on the sapphire substrate. The electrical conduction types and electrical properties of these films depended on the growth temperature, gases flow rates and substrates. The thermal conductivity of the film could be replaced by the substrate, so that the calculated thermoelectric figure-of-merit (Z) for the BP films on the SOI substrate was 10−4–10−3/K at 700–1000 K. Those on the sapphire substrate were 10−6–10−5/K for the direct growth and 10−5–10−4/K for the two-step growth at 700–900 K, indicating that the film on a sapphire by two-step growth would reduce the defect concentrations and promote the electrical conductivity.  相似文献   

14.
Three-layered Pd/Mg1−x Al x /Pd (x = 0, 0.13, 0.21, 0.39) thin films were prepared by means of pulsed laser deposition. In the present Al concentration range, X-ray diffraction analyses showed that the Mg1−x Al x layer was constituted of a single phase Mg(Al) solid solution. The Mg(Al) grains are preferentially orientated along the c-axis and their size decreased (from 18.5 to 10.5 nm) as the Al content increased. Scanning electron microscopy and atomic force microscopy observations indicated that all the films exhibited a globular surface structure. However, the surface roughness of the films decreased as the Al concentration increased. Rutherford backscattering spectroscopy revealed that the Mg–Al layer density (porosity) was strongly dependent on the Al content. Successive hydriding charge/discharge cycles were performed on the different Pd/Mg1−x Alx/Pd films in alkaline media. The highest discharge capacity was obtained with the Pd/Mg0.79Al0.21/Pd film, namely ~85 μAh cm−2 μm−1 or 320 mAh g−1, which corresponds to a H/M atomic ratio of ~0.48 in the Mg–Al layer.  相似文献   

15.
Mg x Zn1−x O:Al (0 ≤ x ≤ 0.6) UV transparent conducting films were deposited on quartz glass by radio frequency magnetron sputtering. Effect of Mg content on structure, optical and electrical properties of Mg x Zn1−x O:Al films was investigated. There is a single phase of basic wurtzite structure of ZnO in Mg x Zn1−x O:Al films at x ≤ 0.4, and of a basic structure of cubic structure of MgO at x ≥ 0.6. The band gap can be varied from 3.27 to 5.90 eV by controlling Mg contents. The resistivity of Mg x Zn1−x O:Al films increase with increasing Mg content x due to the decrease of Al-doping efficiency. The electrical conduction of Mg x Zn1−x O:Al films can be markedly improved by increasing the Al-doping level appropriately and annealing in argon atmosphere at over 500 °C. The maximum band gap of Mg x Zn1−x O:Al films with wurtzite structure was found to be 5.35 eV when Mg content x is 0.4, and the minimum resistivity of 5.4 × 10−4 Ω cm was obtained when the Al/(Zn + Mg + Al) is 0.03 and the annealing temperature is over 500 °C. The average transmittance of Mg x Zn1−x O:Al films was higher than 86% in the wavelength region from 300 (x ≥ 0.4) to 800 nm.  相似文献   

16.
Microstructural and superconducting properties of YBa2Cu3O7−x thin films grownin situ on bare sapphire by pulsed laser deposition using YBa2Cu3O7−x targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant improvement over the undoped YBa2Cu3O7−x films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×106 A/cm2 at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved transport properties.  相似文献   

17.
Spinel LiMn2 − xCoxO4 (0.00 ≦ x ≦ 0.20) powders with small and uniform particle size were successfully synthesized by microwave-induced combustion using lithium nitrate, manganese nitrate, cobalt nitrate, and urea as the starting materials. The LiMn2 − xCoxO4 powders synthesized by microwave-induced combustion were investigated by X-ray diffractometer (XRD), thermogravimeter analyzer (TG), and scanning electron microscopy (SEM). The LiMn2 − xCoxO4 samples were used as cathode materials in lithium-ion batteries, whose discharge capacity and electrochemical characteristics such as the cycling performance were also investigated. The results revealed that the LiMn2 − xCoxO4 cell synthesized by microwave-induced combustion provided a high initial capacity and excellent reversibility compared to the material prepared by solid-state reaction method.  相似文献   

18.
Liquid phase epitaxy (LPE) was used to grow (1−x)Pb(Zn1/3Nb2/3)O3xPbTiO3 (PZNT) films on different substrates. The morphology and epitaxial relationship of PZNT films with these substrates were investigated by optical microscopy and XRD. It was found that PZNT grains on planes of (001) MgO, (001) LaAlO3 (LAO) and two specific planes of SrTiO3 (STO), i.e. (110) or (111), distribute randomly and show no evident epitaxial relationship with these substrates. However PZNT films on (001) STO substrates exhibit very encouraging in-plane epitaxial relation: [100](001)PZNT // [100](001)STO, which was observed directly by OM, SEM and further confirmed by X-ray diffraction.  相似文献   

19.
Superfine powders (~100 nm) with compositions of (1 − x)(Bi0.5Na0.5)0.94Ba0.06TiO3 + xNb5+ (BNTBT6 + xNb) with x from 0 to 0.02 were synthesized by an improved citrate sol–gel method using Nb2O5 as Nb5+ source. The sintering behavior, microstructure, and various electrical properties of BNTBT6 + xNb ceramics were investigated. The results indicated that the addition of a small amount of Nb5+ has no remarkable effect on the crystal structure and grain morphology, but the electrical properties of the ceramics are obviously influenced. The BNTBT6 + 0.005Nb compositions exhibit enhanced densification behavior and improved electrical properties of a piezoelectric constant d 33 ~ 205 pC/N and a planar electromechanical coupling factor k p ~ 33%.  相似文献   

20.
The data of M?ssbauer emission spectroscopy on 67Cu(67Zn) and 67Ga(67Zn) isotopes show that holes appearing as a result of the Sr2+ substitution for La3+ in the La2 − x Sr x CuO4 crystal lattice are localized predominantly at oxygen atoms occurring in the same atomic plane as the copper atoms. In contrast, electrons appearing as a result of the Ce4+ substitution for Nd3+ in the Nd2 − x Ce x CuO4 crystal lattice are localized in the copper sublattice. These results are consistent with the model assuming that a mechanism responsible for the high-temperature superconductivity in La2 − x Sr x CuO4 and Nd2 − x Ce x CuO4 crystal lattices is based on the interaction of electrons with two-site two-electron centers possessing negative correlation energies (negative-U centers).  相似文献   

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