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1.
The heat capacity (C
p
0) of the tellurite glasses
$\begin{gathered}
(TeO_2 )_{0.70} (ZnO)_{0.15} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (I), \hfill \\
(TeO_2 )_{0.75} (ZnO)_{0.10} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (II),and \hfill \\
(TeO_2 )_{0.75} (ZnO)_{0.15} (Na_2 O)_{0.05} (Bi_2 O_3 )_{0.05} (III) \hfill \\
\end{gathered}
$\begin{gathered}
(TeO_2 )_{0.70} (ZnO)_{0.15} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (I), \hfill \\
(TeO_2 )_{0.75} (ZnO)_{0.10} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (II),and \hfill \\
(TeO_2 )_{0.75} (ZnO)_{0.15} (Na_2 O)_{0.05} (Bi_2 O_3 )_{0.05} (III) \hfill \\
\end{gathered}
相似文献
2.
Hiroyuki Sasakura Yoshiya Akagi Masashi Tanaka Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2010,23(7):1381-1384
New Pb-based layered cuprates containing boron with the 1232 structure have been synthesized in the (Pb0.5B0.5)Sr2(Er3−x−y
Ce
x
Sr
y
)Cu2O
z
system. Nearly the single 1232 phase samples are obtained for the nominal composition of 1.6≤x≤1.9 and y=0.2. A sample with the composition of (Pb0.5B0.5)Sr2(Er1.2Ce1.6Sr0.2)Cu2O
z
shows resistivity-dropping phenomenon below 10 K and it shows a diamagnetic signal at about 9.0 K, though the superconducting
volume fraction is very small. From these results, the sample may well be a new Pb-based superconductor with the 1232 structure. 相似文献
3.
The multicomponent refractory oxide system Zn2 − x
(Ti
a
Zr
b
)1 − x
Fe2x
O4 (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0–1.0; Δx = 0.05) has been studied by X-ray diffraction, using samples prepared by melting appropriate metal oxide mixtures in a low-temperature
hydrogen-oxygen plasma. Two phases, both with wide homogeneity ranges, have been identified: α-phase, with a cubic inverse
spinel structure, and β-phase, with a tetragonal inverse spinel structure. The phase boundaries in the system have been determined.
Structural data are presented for about 100 solid solutions. 相似文献
4.
S. L. Young T. C. Wu L. Horng C. H. Lin H. Z. Chen M. C. Kao C. R. Ou N. F. Shih J. B. Shi 《Journal of Superconductivity and Novel Magnetism》2010,23(6):953-956
The ceramic composites, (La0.7Pb0.3MnO3)1−x
(SiO2)
x
, with diluted magnetic properties are prepared using solid-sate sintering route. Magnetization processes of (La0.7Pb0.3MnO3)1−x
(SiO2)
x
composites are explored in this study. Ferromagnetism is gradually attenuated due to the magnetic dilution induced by the
increase of SiO2 content. Clearly, irreversible behavior is observed in the zero-field cooling and the field cooling (ZFC–FC) curves at a
low field of 100 Oe. Saturation magnetization decreases as x increases while ferromagnetic transition temperature remains around 346 K for all composites. All the composites exhibit
ferromagnetic hysteresis behavior which can be modeled by the law of the approach to saturation in the form M=M
S(1−a/H). The term a/H expresses the deviation of magnetization from saturation. The smaller factor a for La0.7Pb0.3MnO3-rich samples results in sharper square curve which should be associated with the long-range spin order of ferromagnetic coupling. 相似文献
5.
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
6.
A new series of superconducting mercury-based layered cuprates has been synthesized. X-ray diffraction indicates that the compounds with formula Hg0.8W0.2Sr2Y1–x
Ca
x
Cu2O6+ (0.3x0.6) exhibit the 1212 structure with space groupP
4/mmm
. The investigation of superconductivity determined by electrical resistance measurement shows that the superconducting transition temperature (T
c
, onset) of Hg0.8W0.2Sr2Y0.4Ca0.6Cu2O6+ is up to 94 K. 相似文献
7.
The electrical conductivity, band gap, dielectric permittivity, and molar polarizability of Zn2(Ti
a
Sn
b
)1 − x
Zr
x
O4 solid solutions have been determined. All of the synthesized samples are dielectrics with semiconducting behavior of conductivity.
The phase diagram of the Zn2TiO4-Zn2SnO4-Zn2ZrO4 system is presented. 相似文献
8.
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
9.
A. Younis A. Hussain M. Asghar A. Manzoor S. Javed 《Journal of Superconductivity and Novel Magnetism》2011,24(4):1327-1332
The dielectric properties of Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
(q=0, 0.5, 1.0 1.5) superconductor samples were studied at two temperatures of 80 and 290 K by capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 10 MHz. We have presented the measurements of the dielectric constants (ε′ and ε″), dielectric loss factor (tan δ) and ac-conductivity (σ
ac) as a function of frequency and temperature. A negative capacitance (NC) experience has been observed, which is most likely
due to different contact electrodes and superconductor samples’ Fermi levels. Since metals have their Fermi levels higher
than ceramics, there is a flow of the carriers from the ceramic samples towards the metal electrodes. The dielectric polarization
phenomenon is observed, which is due to dislodgment of mobile charges from their equilibrium position relative to fixed charges
of the reservoir layer. The improved inter plane coupling promoted by Mg substitution at Ca site would change the dielectric
response of Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
superconductors. To observe such effects in Mg doped Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
superconductors, di- electric measurements were carried out both at room temperature (290 K) and in the superconducting state
closer to the boiling point of liquid nitrogen (80 K). The excess conductivity arising due to superconducting state of material
has been determined, and its role in the mechanism of superconductivity is suggested. The negative dielectric constant (ε′) and dielectric loss factor (tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 80 K may enhance the polarizability and hence
the dielectric constants (ε′ and ε″). 相似文献
10.
New NASICON type materials of composition, Li3−2x
Al2−x
Sb
x
(PO4)3 (x = 0·6 to 1·4), have been prepared and characterized by powder XRD and IR. D.C. conductivities were measured in the temperature
range 300–573 K by a two-probe method. Impedance studies were carried out in the frequency region 102−106 Hz as a function of temperature (300–573 K). An Arrhenius behaviour is observed for all compositions by d.c. conductivity
and the Cole-Cole plots obtained from impedance data do not show any spikes on the lower frequency side indicating negligible
electrode effects. A maximum conductivity of 4·5 × 10−6 S cm−1 at 573 K was obtained for x = 0·8 of the Li3−2x
Al2−x
Sb
x
(PO4)3 system. 相似文献
11.
The effect of Pb doping on the superconducting properties of (Cu0.5−x
Pb
x
Tl0.5)Ba2Ca2Cu3O10−δ
(x=0.0, 0.15, 0.25, 0.35) samples has been investigated. Lead is doped in Cu0.5Tl0.5Ba2O4−δ
charge reservoir layer and at the CuO2 planar sites. A multiphase material is achieved with the doping of Pb at the CuO2 planar sites; however, a predominant single-phase (Cu0.5−x
Pb
x
Tl0.5)Ba2Ca2Cu3O10−δ
(x=0.0, 0.15, 0.25, 0.35) material is synthesized with the doping of Pb at the charge reservoir layers. Formation of multiphase
material with the doping of lead at the planar sites showed that its substitution at the planar site is not possible and the
formation of PbO2 planes is less likely. In the samples doped at the charge reservoir layer, the zero critical temperature [T
c
(R=0)] is systematically depressed with the increased concentration of lead. The T
c
(R=0) and magnitude of the diamagnetism are enhanced after post-annealing the samples in oxygen atmosphere. An apical oxygen
mode is observed around 438 cm−1 in undoped samples, which is shifted to 457–461 cm−1 in the Pb-doped samples. This shift in the peak position is most likely associated with the connectivity of apical oxygen
atoms with Pb atoms of (Cu0.5−x
Pb
x
Tl0.5)Ba2O4−δ
(x=0.0, 0.15, 0.25, 0.35) charge reservoir layers. The presence of Pb in the charge reservoir layer and its increased concentration,
somehow, stops the flow of mobile carriers to the conducting CuO2 planes. The decreased density of mobile carriers diminishes the critical temperature and magnitude of diamagnetism in the
final compound. The increased oxygen diffusion in the unit cell achieved by post-annealing in oxygen replenishes the concentration
of carriers in conducting CuO2 planes, which increases the T
c
(R=0) and the magnitude of diamagnetism. These experiments have shown that the density of mobile carriers plays a vital role
in the mechanism of superconductivity and their depressed density suppresses the superconductivity parameters. 相似文献
12.
R. L. Neiman J. Giapintzakis D. M. Ginsberg J. M. Mochel 《Journal of Superconductivity》1995,8(3):383-389
We have measured the in-plane Hall effect and in-plane resistivity of cobalt-doped YBa2Cu3O7– (YBCO) single-crystal samples. The concentration of cobalt ranged from 1 to 3%. As the applied field was varied, a sign reversal of the Hall resistivity was seen for 1 and 2% Co-doped samples, but not for the 3% sample. Our results are expressed in terms of conductivities, as recently recommended by the work of Dorseyet al. and Kopninet al. In the mixed state just below the superconducting transition temperatureT
c, the Hall conductivity
xy is the sum of two terms,C
1/H andC
2H, whereC
1 andC
2 are field-independent but temperature-dependent. As previously observed by Ginsberg and Manson for undoped YBCO, the coefficientC
1 is approximately proportional to
2 andC
2 is approximately linear in, where = 1–(T/T
c
). The values ofC
1 andC
2 are presented for each cobalt concentration. 相似文献
13.
New cuprates with nominal composition (Pb0.8W0.2)Sr2(Nd1 – x
Ca
x
)Cu2O7 – (0x1) were synthesized by solid-state reaction in N2. The crystal structure was characterized by X-ray powder diffraction (XRD) as tetragonal. Direct current electrical resistance measurements were applied to check the existence of superconductivity in these cuprates. Superconductivity with T
c (onset) up to 82 K is observed when x = 0.6. Synthesis in N2 is necessary in obtaining superconductivity in these cuprates. Preparation in air or post-treatment in flowing oxygen destroys superconductivity. A comparison is made with previous Pb-based 1212 superconducting oxides. The valence of Pb and the possible position of W in the lattice are discussed. 相似文献
14.
We have synthesized Ba1 − x
(Zn1/2W1/2)O3 − x
and Ba(Zn1/2 − y
W1/2)O3 − y/2 barium tungstates with different deviations from cation stoichiometry (x = 0.01–0.05, y = 0.01–0.05), determined the phase composition of ceramics fabricated from the tungstates, and investigated their electrical
properties. Even slight deviations from cation stoichiometry in Ba(Zn1/2W1/2)O3 lead to the formation of the scheelite phase BaWO4, and its content increases with heat-treatment temperature. Barium or zinc deficiency in the systems studied improves the
sintering behavior of Ba(Zn1/2W1/2)O3 and increases the degree of 1: 1 B-site cation ordering, which in turn ensures an increase in microwave quality factor, Q. 相似文献
15.
16.
Hengwei Liu Aimin Sun Yanzhong Lu Yaotong Ma Jinyuan Ma Guidan Wei Long Zheng 《Journal of Superconductivity and Novel Magnetism》2010,23(8):1525-1528
A series of polycrystalline samples of Mg1−x
Zn
x
(B1−x
C
x
)2 (x=0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) were synthesized by a conventional solid-state reaction method under a background
pressure about 10−3 Pa. Phase identification, crystal structure and superconducting transition temperature (T
c) were studied by means of X-ray diffraction (XRD) and resistivity measurements. The results indicated that the lattice parameters
a and c show no clear trend in their changes with increasing doping level, and it turned out that the dopants had a marked effect
on the crystal-lattice parameters and changed the crystal structure of the samples. The T
c for Mg1−x
Zn
x
(B1−x
C
x
)2 decreased with C and Zn doping, but the rate of decrease was slower than single C-doped. We propose that the suppression
of T
c by doping originates largely from the structural change. 相似文献
17.
I. A. Verbenko O. N. Razumovskaya L. A. Shilkina L. A. Reznichenko K. P. Andryushin 《Inorganic Materials》2009,45(6):702-708
The influence of past history on the possibility of obtaining high-density ferroelectric ceramics of solid solutions [(Na0.5K0.5)1 − x
Li
x
](Nb1 − y − z
Ta
y
Sb
z
)O at x = 0–0.14, y = 0, 0.1, 0.2, and z = 0–0.1 is identified. The dynamics of behavior of materials under a field in the process of polarization is evaluated. The
relative dielectric permeability of samples in a wide range of temperatures (20–700°C) and frequencies (25 Hz-1 MHz) of a
variable electric field is studied. On the basis of study of dielectric, piezoelectric, and elastic properties of solid solutions,
prospective objects for further technological elaboration and modification of chemical composition with the goal of improving
the electrophysical parameters are selected.
Original Russian Text ? I.A. Verbenko, O.N. Razumovskaya, L.A. Shilkina, L.A. Reznichenko, K.P. Andryushin, 2009, published
in Neorganicheskie Materialy, 2009, Vol. 45, No. 6, pp. 762–768. 相似文献
18.
M. B. Maple C. C. Almasan C. L. Seaman S. H. Han K. Yoshiara M. Buchgeister L. M. Paulius B. W. Lee D. A. Gajewski R. F. Jardim et al. 《Journal of Superconductivity》1994,7(1):97-106
Investigations of Y1–x
M
x
Ba2Cu3O7–
(M=Ce, Th)c-axis oriented thin film specimens show that the rate of depression ofT
c
withx is larger for M=Th, than for M=Ce and Pr, and suggest that Ce, like Th, is tetravalent in this compound. Hall effect measurements on Y1–x
Pr
x
Ba2Cu3O7–
single crystals reveal aT
2 dependence of the cotangent of the Hall angle in the normal state and a negative Hall anomaly belowT
c
in the superconducting state, in agreement with recent reports. Our research shows that the depth, , of the negative Hall signal scales withT/T
c
and that the maximum value of decreases linearly withx and vanishes atx0.24. Magnetoresistance measurements on Y1–x
Pr
x
Ba2Cu3O7–
single crystals indicate that the irreversibility lineH(T
*) obeys a universal scaling relation characterized by anm=3/2 power law nearT
c, with a crossover to a more rapid temperature dependence of belowT/T
c
0.6, similar to that observed for polycrystalline specimens. 相似文献
19.
S. M. Hasnain M. Mumtaz Nawazish A. Khan 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1653-1657
The effect of synthesis temperature on the superconducting properties of (Cu1−x
Tl
x
)Ba2Ca3Cu4O12−δ
(CuTl-1234) samples has been explored. Almost all the superconducting parameters studied in this research work are observed
to be suppressed with the increase of synthesis temperature beyond 880 °C, which may be due to impurities caused by the volatility
of some constituents such as thallium and oxygen deficiencies as well in the final compound. The Fluctuation Induced Conductivity
(FIC) analysis has shown a decrease in the cross-over temperature (T
0) and the shift of three-dimensional (3D) Aslamasov–Larkin (AL) regions to the lower temperature with the increase of synthesis
temperature beyond 880 °C. A direct correlation between the cross-over temperature (T
0), the zero temperature coherence length {ξ
c
(0)}, the zero resistivity critical temperature {T
c
(R=0)} as well as carrier concentration has also been observed. 相似文献
20.
M. Mumtaz Nawazish A. Khan Faheem Ashraf 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1985-1989
The relatively higher electronegative elements (M = Pd, Nb, Bi, Hg) have been partially doped at Tl sites in Cu0.5Tl0.5−x
M
x
Ba2O4−δ
(x=0,0.25) charge reservoir layer of Cu0.5Tl0.5−x
M
x
Ba2Ca2Cu3O10−δ
superconductor. These elements may retain more oxygen in the charge reservoir layer due to their higher electronegativity
as compared to Tl, and the higher population of oxygen in the charge reservoir layer can optimize the charge carriers’ density
in the conducting CuO2 planes. The optimum density of mobile charge carriers in the conducting CuO2 increases Fermi wave-vector K
F and Fermi velocity v
F of the carriers, which results in the improvement of superconducting properties of the material. 相似文献
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