共查询到20条相似文献,搜索用时 15 毫秒
1.
Alev Ayd?ner Bakiye ?ak?r Mehmet Ba?o?lu Hironori Seki Atikorn Wongsatanawarid Masato Murakami Ekrem Yanmaz 《Journal of Superconductivity and Novel Magnetism》2012,25(2):391-397
In this work, single-crystal samples 20 mm in diameter were grown by a cold top-seeding method. In order to study the effect
of an Y2O3 buffer layer, a compacted precursor was located in a crucible on a buffer layer of freely poured Y2O3 powder. The YBCO bulk samples were carefully prepared in the same chemical composition. In order to examine the homogeneity
of the samples, rectangular specimens were cut from a sample. The structural orientation of the specimens was measured by
a X-ray diffractrometer (XRD). The microstructure was observed with a Scanning Electron Microscope (SEM). The magnetic properties
were measured using a Vibrating Sample Magnetometer (VSM) at 77 K with the applied magnetic field parallel to the c-axis. As a result only (00l) peaks were observed in X-ray diffraction data, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Also the cut samples exhibited very fine Y211 inclusion distributed in the bulk sample
observed in SEM micrographs. The critical current density J
c (A/cm2) has been estimated by the extended Bean model. The maximum value of the critical current density at 77 K is 5.2×104 A/cm2 in a self-field. The trapped magnetic field measurements of the samples were performed by using Hall probe scanning device
with static field of 0.5 T at 77 K. The single-domain sample exhibits a trapped field of 1140 G at 77 K. 相似文献
2.
Hua Wang Zhu Huang Ji-wen Xu Ling Yang Ming-fang Ren 《Journal of Materials Science: Materials in Electronics》2010,21(11):1115-1118
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
3.
Masashi Tanaka Hiroyuki Sasakura Yoshiya Akagi Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1479-1483
New Pb-based 1212 layered cuprates containing sulfur have been synthesized in the (Pb0.75S0.25) Sr2 (Y1−x
Ca
x
) Cu2O
z
system. X-ray diffraction analysis shows that the almost single-phase samples are obtained within a region of 0.0≤x≤0.5. The crystal structure of each sample has a tetragonal symmetry with the typical lattice constants a=0.3837 nm and c=1.186 nm. As Ca content x is increasing, the semiconductor-like behavior is suppressed. But after only annealing under ambient O2 pressure, none of the samples show any trace of superconductivity. On the other hand, when the samples are annealed under
high O2 pressure of about 13.6 MPa, they show resistivity dropping phenomenon in a region of 0.5≤x≤0.7. Among them, the lowest resistivity sample with x=0.6 has an onset temperature of the resistivity dropping at about 22.5 K. Moreover, this sample shows a diamagnetic signal
at about 21.5 K. These phenomena are attributed to superconductivity. 相似文献
4.
C.E.A. Grigorescu L. Tortet L. Argeme S. Granville F. Budde G.V.M. Williams A. Tonetto C. Logofatu 《Thin solid films》2008,516(7):1617-1621
We study the effect of annealing on structure, morphology and optical properties of nanocrystalline films of GaN, GaN:O and GaN:Mn prepared by ion assisted deposition on silicon, quartz and glassy carbon substrates. Blisters and holes having diameters proportional with the thickness of the film were observed in GaN:O deposited on silicon and glassy carbon. The Mn excess in GaN:Mn turns through annealing into MnxNy islands. The degree of short- and intermediate-range order in the films was investigated by micro-Raman spectroscopy, extending to about 3 nm for gallium oxynitride films annealed to 973 K and to more than 10 nm in GaN samples. A diminished oxygen content following the annealing procedures on GaN:O samples is noticed from the reduced intensity of the oxygen mode at 1000 cm− 1 in the Raman spectra. This observation is supported with X-ray photoemission spectroscopy measurements. The presence of oxygen at concentrations above 15at.% in the films leads to an abrupt nanocrystalline-amorphous transition. 相似文献
5.
Hiroyuki Sasakura Yoshiya Akagi Masashi Tanaka Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2012,25(2):305-309
New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb0.75P0.25)Sr2- (RE2–x–y
Ce
x
Sr
y
)Cu2O
z
(RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single phase samples are obtained for 0.5≤x≤1.0 and y=0.1 in the cases of RE = Nd, Dy, Ho, Er, Tm, Yb and Y, while for 0.3≤x≤1.0 and y=0.1 in the cases of RE = Sm, Eu and Gd. The samples crystallize in a tetragonal lattice, the lattice parameters a and c are decreasing with the decrease of the ionic radius of the RE element. Even after annealing under 143 atm O2 atmosphere at 400 °C, almost all the samples with the common values x=0.5 and y=0.1 are semiconductors with a transport process followed by three-dimensional variable range hopping. However, the samples
of RE = Sm, Eu and Gd, which are of almost single 1222 phase, even for x=0.3 and y=0.1, show superconductivity with the onsets at about 25 K, 20 K and 22 K, respectively. Through this study, we find very
important procedure for discovery of new superconducting 1222 compound. 相似文献
6.
Masashi Tanaka Hiroyuki Sasakura Yoshiya Akagi Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2011,24(7):2037-2039
We have already reported on substitution effects of Ba for Sr in the sulfur contained Pb-based 1212 compound with the composition
of (Pb0.75S0.25)(Sr2−x
Ba
x
) (Y0.4Ca0.6)Cu2O
z
. It was found that each sample with x=0.3–0.6 showed a resistivity drop originating from superconductivity, and the highest onset temperature of the drop was about
32 K for a sample with x=0.5, but the volume fraction was very small. More recently, we have investigated effect of high-pressure O2 annealing on superconductivity of the Ba-substituted samples with x=0.4–0.6. As a result, the sample with x=0.5 is found to show an onset of the resistivity drop at the highest temperature of about 41.7 K and it shows an onset of
the diamagnetic signal at about 42.0 K. These transition temperatures are higher by ∼10 K than those of the previously reported
sample with x=0.5. Moreover, the superconducting volume fraction is increasing more by the high-pressure O2 annealing. These results indicate that the high-pressure O2 annealing effectively promotes superconductivity of the present (Pb0.75S0.25)(Sr2−x
Ba
x
)(Y0.4Ca0.6)Cu2O
z
system. 相似文献
7.
H. Sasakura Y. Akagi M. Tanaka S. Tsukui M. Adachi 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1623-1626
New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb,P)Sr2(Eu,Ce,Sr)2 Cu2O
z
system. From X-ray powder diffraction study, almost the single 1222 phase samples are found to be obtained in a considerable
wide composition area of 0.3≤x≤1.2 for the nominal composition of (Pb0.75P0.25)Sr2(Eu1.9−x
Ce
x
Sr0.1) Cu2O
z
. The crystal structure for each sample has a tetragonal symmetry and the typical lattice parameters are a=0.3851 nm and c=2.922 nm. After annealing under 143 atm O2 atmosphere at 400 °C, a sample with x=0.3 among the almost-single phase samples shows an onset of resistivity-drop at the highest temperature of about 22 K and
zero-resistivity at the highest temperature of about 12 K, then this sample also shows an onset of diamagnetic signal at about
20 K. These phenomena are found to originate from superconductivity of the new 1222 phase. 相似文献
8.
Mo, Al2O3 single layer, Mo-Al2O3 granular cermet layer, Mo/Al2O3 tandem and an optimized Mo-Al2O3 multilayer coating with a double cermet layer configuration were deposited on stainless steel substrates by magnetron sputtering technique. The samples were annealed in vacuum at different temperatures ranging from 350 °C to 1000 °C for 2-5 h to evaluate their thermal stability. The spectral absorbance and thermal emissivity for the multi-layer selective coatings in the region of 1.3-25 μm were 0.91-0.93 and 0.19-0.27, respectively, depending on heat treatment temperature. Increasing annealing temperature has more obvious influence on the rise of emissivity than the drop of spectral absorbance. The microstructure, surface morphology, composition distribution and diffusion for various films before and after high temperature aging were investigated employing scanning electronic microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Fe2O3, as a diffusion barrier between Mo layer and SS substrate, effectively holds back the presence of Mo2C and Fe2MoC complex phases. Al2O3 is a stable phase even at 1000 °C for 3 h. However, defects such as widened boundaries, cracks and holes, which could appear in Al2O3 layer when heated at higher temperature than 650 °C, will provide the paths of Mo diffusion. Two diffusion modes of Mo, including inner self-congregation of Mo inside the cermet layer and Mo infiltration through the Al2O3 layer in Mo/Al2O3 tandem at 800 °C for 5 h, were observed after annealing. 相似文献
9.
X-ray diffraction (XRD), electron paramagnetic resonance (EPR), and magnetic susceptibility measurements have been employed
to investigate the samples from the (Gd2O3)
x
·(B2O3)(60−x)·(ZnO)40 (0 ≤ x ≤ 20 mol%) system. The XRD pattern for the prepared samples shows that the vitreous phase is present only for x ≤ 15 mol%. For the samples containing 20 mol% Gd2O3 the presence of a unique crystalline phase, GdBO3, embedded in a vitreous matrix was evidenced. In this case the XRD patterns show the presence of nanometer sized crystals
(64 nm) in a glassy matrix. The EPR spectra of the studied samples exhibit three important features with effective g-values
of ≈6, 2.8, 2.0 and a weaker feature at g ≈ 4.8. For low Gd2O3 contents (x < 3 mol%), the EPR spectra have the typical ‘‘U’’-type shape. For higher contents of Gd2O3 (x ≥ 3 mol%), the spectral features are broadened and finally are dominated by a single broad absorption line located at g ≈ 2.0. This broad EPR line is associated to the Gd3+ ions present predominantly as clustered species. Magnetic susceptibility data show that for x > 1 mol% the Gd3+ ions are present not only as isolated species but also as species coupled through antiferromagnetic exchange interactions. 相似文献
10.
In the experiment, nano-structured and amorphous ultrathin Ru-Ge interlayers (∼15 nm in thickness) were deposited between Cu(Ru) alloy film and Si substrate via co-sputtering functioning as preventive diffusion barrier layers. After annealing at different temperatures, X-ray diffraction and four-point probe method revealed that the amorphous Ru-Ge layer effectively suppressed the Cu diffusion into Si substrate up to a temperature of at least 873 K; however, it is less than 773 K for the nano-structured Ru-Ge layer. A self-formed amorphous multilayer of Ru(RuOx)/RuGexCuy could be attained by annealing Cu/Cu(Ru)/Ru-Ge(amorphous)/Si system at a very low temperature (even 473 K). The results proved that the amorphous Ru-Ge system could self-form the multilayer diffusion barrier before the diffusion reaction between Cu and Si and improved the thermal stability of the Cu interconnection significantly. 相似文献
11.
Tantalum is used as a diffusion barrier in the superconducting Nb3Sn composite-wire manufactured by the bronze method. In order to examine the consumption behavior of the Ta barrier during
annealing in the bronze method, the kinetics of the reactive diffusion between Ta and a bronze was experimentally observed
using sandwich diffusion couples composed of Ta and a Cu–9.3Sn–0.3Ti alloy. The (Cu–Sn–Ti)/Ta/(Cu–Sn–Ti) diffusion couples
were isothermally annealed at temperatures of T = 973–1053 K for various times up to t = 1462 h. Owing to annealing, Ta9Sn is formed as a uniform layer at the initial (Cu–Sn–Ti)/Ta interface in the diffusion couple, and gradually grows mainly
toward Ta. The mean thickness of the Ta9Sn layer is proportional to a power function of the annealing time. However, the exponent of the power function is equal to
unity at t < t
c but smaller than 0.5 at t > t
c. Thus, the transition of the rate-controlling process for the growth of Ta9Sn occurs at t = t
c. The critical annealing time t
c takes values of 1.83 × 106, 4.63 × 105, and 5.98 × 105 s at T = 973, 1023, and 1053 K, respectively. The growth of Ta9Sn is controlled by the interface reaction at the migrating Ta9Sn/Ta interface in the early stages with t < t
c but by the volume and boundary diffusion across the Ta9Sn layer in the late stages with t > t
c. Due to the transition of the rate-controlling process, the growth rate is always much smaller for Ta9Sn than for Nb3Sn. As a result, Ta works as an effective barrier against the diffusion of Sn from the bronze to the Cu stabilizer in the
superconducting Nb3Sn composite-wire. 相似文献
12.
Carlo Paternoster Alberto Fabrizi Raimondo Cecchini Mohamad El Mehtedi Patrick Choquet 《Journal of Materials Science》2008,43(10):3377-3384
Thin CrN
x
coatings are often used as protective coatings for steel. In these applications, coated parts might be subjected to high
temperatures that can alter the coatings structural and mechanical properties. In this work, the properties of nanometric
CrN
x
coatings deposited by reactive magnetron sputtering on AISI 304L stainless steel were studied by transmission electron microscopy,
glazing incident X-ray diffraction, Atomic Force Microscopy, and nanoindentation. The effect of annealing, both in air and
vacuum, on the coating crystal structure, surface morphology and hardness were also investigated. It was found that annealing
in vacuum-induced phase transformation from CrN to Cr2N, while after annealing in air only Cr2O3 phase was present. Surface roughness did not increase for annealing in vacuum. CrN
x
coatings with higher Cr2N phase content showed lower roughness increase for annealing in air. Measured hardness was >10 GPa for as-deposited CrN
x
samples. An increase in hardness up to >20 GPa was found for vacuum-annealed samples. 相似文献
13.
A procedure was proposed for low-temperature vapor-phase In doping of Pb1 – x
Sn
x
Te films grown by molecular-beam epitaxy on BaF2 substrates. Diffusion annealing was carried out in a hydrogen atmosphere in the presence of a vapor source identical in composition to the film and a dopant source at temperatures which were, in most cases, no higher than the growth temperature (300–460°C). The effect of diffusion annealing on the composition, transport properties, and homogeneity of both undoped and In doped films was examined. The results suggest that indium is transported in the vapor phase in the form of indium tellurides resulting from the reaction between Te vapor and liquid In. 相似文献
14.
Khaled M. Elsabawy 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1853-1861
Hafnium was used as a softener dopant to replace at magnesium sites of Mg1−x
Hf
x
B2 regime (where x=0.0, 0.05, 0.1, 0.2, and 0.4 mole). Samples were prepared via high temperature solid state reaction technique depending upon
diffusion mechanism of Mg-vapor ions through hafnium–boron matrix. The maximum solubility limit of hafnium (n) was found to be ∼0.22 mole. The crystalline lattice constants exhibit slight elongation in the case of the c-axis as x increases. Furthermore, the effect of Hf-doping on the microstructure properties of the MgB2 system was investigated carefully. The SE-microscopic analysis indicated that hafnium ions diffuse regularly through surface
and bulk in case of (x=0.05–0.2 mole). The grain size was estimated and found to be between 0.33 and 1.34 μm. The mechanical tensile strength of
the samples was clearly improved linearly as Hf-content increased, recording the maximum tensile strength of 34.8 MPa for
the sample with x=0.4 mole. A visualization of the Hf-doped MgB2 structure was constructed and investigated to confirm the success of hafnium substitutions at the Mg-sites of the MgB2 superconductor. 相似文献
15.
M. Zargar Shoushtari S. E. Mousavi Ghahfarokhi 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1505-1511
The flux pinning energy and magnetic properties of Bi1.64−x
Pb0.36Cd
x
Sr2Ca2Cu3O
y
(BPCSCCO) with x=0.0, 0.02, 0.04 and 0.06 were studied. A series of Bi-2223 superconductor samples with a nominal composition of BPCSCCO was
synthesized and the effect of Cd substitution for Bi was investigated. As a result, Cd addition has been found to improve
the superconducting properties of the Bi-Pb-Sr-Ca-Cu-O system. The effects of the annealing time and the amount of Cd doping
on the structure, AC magnetic susceptibility, ρ–T curves and flux pinning energy were investigated. Also, for all samples the relation between the current and voltage in the
mixed state was found to follow the model relationship V=α
I
β
. The maximum value of β is 22.30, which is obtained for the sample with an annealing time of 270 h and a Cd content of 0.04. 相似文献
16.
Y. Sun C. L. Wang H. C. Wang H. Peng F. Q. Guo W. B. Su J. Liu J. C. Li L. M. Mei 《Journal of Materials Science》2011,46(15):5278-5281
Ceramic samples of La0.1Y
x
Sr0.9–x
TiO3 with different yttrium concentration have been synthesized by conventional solid state reaction technique, and their thermoelectric
properties have been investigated. X-ray diffraction characterization confirms that the main crystal structure is of perovskite,
but with a small amount of second phase of Y2Ti2O7 for samples with x = 0.05, 0.08, and 0.10. SEM images indicate all ceramic samples are dense and compact, and the largest grain size appears
in sample with x = 0.03 and 0.05. Also the second phase can also be identified from the SEM images for x = 0.05, 0.08, and 0.10 samples. Electrical conductivity and Seebeck coefficient of samples have been measured in the temperature
range between 300 and 1100 K. With increasing of yttrium concentration, electrical resistivity decreases, and reaches 0.8 mΩ cm
for x = 0.10 sample at room temperature. The absolute Seebeck coefficients increase monotonically with increasing temperature in
the whole temperature range. Sample with x = 0.03 exhibits the highest absolute Seebeck coefficient 219 μV K−1 at 1059 K, as well as the maximum power factor 11 μW cm−1 K−2 at 624 K. 相似文献
17.
Fang Liu Xin Zhang Kang-Wei Zhu Yu Song Zhen-Hua Shi Bo-Xue Feng 《Journal of Materials Science》2009,44(22):6028-6034
The electrochromic (EC) NiO
x
H
y
films were fabricated through a facile sol–gel method. The formation of high quality NiO
x
H
y
films came from adding the xerogel back into the sol and prolonging the annealing time at gradually increasing temperature
up to 250 °C. Scanning electron microscopy and atomic force microscopy characterizations indicated films were compact, homogenous,
and smooth. Glance angle X-ray diffraction investigation testified NiO
x
H
y
films were of poor crystallization. The Fourier transform infrared, and thermogravimetry and differential thermal analysis
showed that films contained the mixture of NiO, Ni(OH)2, NiOOH, water, and organic substance. With the increasing of the xerogel ratio, the optical absorbance and reflectance of
films had larger differences between the colored and bleached state, respectively. The film with the xerogel ratio of 1:5
showed excellent EC properties with a transmittance contrast as high as 60.88% at λ = 560 nm, which was higher than other
sol–gel nickel oxide films reported. 相似文献
18.
Thin films of (WO3)1-x-(Fe2O3)x composition were deposited by thermal evaporation on glass substrates and then all samples were annealed at 200-500 °C in air. Optical properties such as transmittance, reflectance, optical bangap energy, and the optical constants of the “as deposited” and the annealed films were studied using ultraviolet-visible spectrophotometry. It was shown that the annealing process changes the film optical properties which were related to Fe2O3 concentration. Moreover, using X-ray photoelectron spectroscopy, we have indicated that WO3 is stoichiometric, while iron oxide was in both FeO and Fe2O3 compositions so that the FeO composition converted to Fe2O3 after the annealing process. Using atomic force microscopy, it was observed that surface of the “as deposited” films were smooth with a nanometric grain size. The film surface remained unchanged after annealing up to 300 °C. Surface roughness and the grain size of the films with x = 0, 0.05, and 0.75 highly increased at higher annealing temperatures (400 and 500 °C), but were nearly unchanged for medium x-values (0.3 and 0.4). 相似文献
19.
Hiroyuki Sasakura Yoshiya Akagi Masashi Tanaka Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2012,25(2):245-248
We previously reported on the synthesis of new Pb-based 1222 superconductor containing phosphorus in the (Pb0.75P0.25)Sr2(Eu1.9−x
Ce
x
Sr0.1)Cu2O
z
system. Recently, we have discovered new members of the Pb-based 1222 superconductor containing phosphorus in the (Pb0.75P0.25)Sr2(Ln1.9−x
Ce
x
Sr0.1)Cu2O
z
(Ln=Sm and Gd) systems. In each system, it is found that the samples of almost the single 1222 phase can be obtained for
a wide composition area of 0.3≤x≤1.0. After annealing under 143 atm O2 atmosphere at 400 °C, each sample of Ln=Sm and Gd with x=0.3 is found to show an onset of resistivity-drop at about 28 K and at about 24 K, respectively. Moreover, each samples of
Ln=Sm and Gd is found to show an onset of diamagnetic signal at about 25 K and about 22 K, respectively. From these facts,
these samples of Ln=Sm and Gd are found to be new members of the Pb-based 1222 superconductor containing phosphorus. 相似文献
20.
Hiroyuki Sasakura Yoshiya Akagi Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2009,22(8):755-758
We previously reported on the discovery of new Pb-based 1222 cuprates containing boron in the (Pb0.5B0.5)Sr2(RE2−x−y
Ce
x
Sr
y
)Cu2O
z
(RE = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. However, none of the cuprates was a superconductor, but a semiconductor
with the conduction process of a three-dimensional variable range hopping at low temperatures, despite annealing under O2 atmosphere at 100 atm and 400 °C. Recently, we have discovered that some samples showed superconductivity in the (Pb0.5B0.5)Sr2(Y1.9−x
Ce
x
Sr0.1)Cu2O
z
system. Among them, the sample with x=0.45 shows the highest zero resistivity temperature at about 10 K and it shows a diamagnetic signal starting at abut 16 K
with lowering temperature. The superconductivity is considered to originate from the 1222 phase. 相似文献