共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Benjaram M. Reddy Gunugunuri K. Reddy Komateedi N. Rao Ibram Ganesh Jose M. F. Ferreira 《Journal of Materials Science》2009,44(18):4874-4882
Titania–silica, titania–alumina, and titania–zirconia mixed oxides (1:1 molar ratio) were prepared by a microwave-induced
solution combustion synthesis technique. The prepared materials were characterized by thermogravimetry/differential thermal
analysis, X-ray diffraction (XRD), Raman spectroscopy, BET surface area, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible
diffuse reflectance spectroscopic (UV–Vis DRS), and Fourier transform infrared (FTIR) techniques to assess their physicochemical
properties. Their photocatalytic activity for the degradation of phenol in aqueous solution under sunlight was studied. XRD
and Raman studies revealed the presence of titania in the form of anatase phase in all the mixed oxides synthesized. The XRD
studies further suggested that titania–zirconia contains an additional (Ti,Zr)O2 phase. UV–Vis DRS results reveal that all samples exhibit absorption maxima near visible region. FTIR results revealed the
presence of Ti–O–Si linkages in the titania–silica sample, which are responsible for its higher activity in the photocatalytic
degradation of phenol under sunlight. 相似文献
3.
H. Khelifi A. Aydi N. Abdelmoula A. Simon A. Maalej H. Khemakhem M. Maglione 《Journal of Materials Science》2012,47(4):1943-1949
Lead-free (1 − x)NaNbO3/xBa(Ti0.5Sn0.5)O3 (x = 0.1, 0.125, 0.15, 0.175, 0.2, and 0.3) ceramics were elaborated by the conventional ceramic technique. Sintering has been
made at 1523 K for 2 h. The crystal structure was investigated by X-ray diffraction with CuKα radiation at room temperature.
As a function of composition, these compounds crystallize with tetragonal or cubic symmetry. Dielectric measurements show
that the materials have a classical ferroelectric behavior for compositions in the range 0.10 ≤ x ≤ 0.15 and relaxor one for compositions in the range 0.15 < x ≤ 0.30. Temperatures T
C or T
m decrease as x content increases. The ferroelectric behavior has been confirmed by hysteresis characterization. For x = 0.1, a piezoelectric coefficient d
31 of 42.146 pC N−1 was obtained at room temperature. The evolution of the Raman spectra was studied as a function of temperature for x = 0.1. 相似文献
4.
M. A. A. Moussa N. M. Al-Hosiny 《Journal of Superconductivity and Novel Magnetism》2011,24(4):1309-1314
The chemical solution nitrate route was used to prepare Y0.5[Yb1−x
Nd
x
]0.5Ba2Cu3O
z
superconducting phase with x=0.1, 0.2 and 0.3. Different calcination temperatures from 870 to 900 °C were used. Both XRD and DSC techniques were utilized
in monitoring the Y0.5[Yb1−x
Nd
x
]0.5Ba2Cu3O
z
superconducting phase and the non-superconducting impurity phases such as BaCuO5, CuO and RE2BaCuO5. These two techniques were used to study the effect of impurity phases on the decomposition temperature of Y0.5[Yb1−x
Nd
x
]0.5Ba2Cu3O
z
superconducting phase. The value of x, the Nd amount, and the calcination temperature both influenced the type and number of impurity phases, which resulted in
changing the eutectic and peritectic reaction temperatures. 相似文献
5.
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
6.
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
7.
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
8.
9.
A. I. Svitan’ko S. A. Novikova D. V. Safronov A. B. Yaroslavtsev 《Inorganic Materials》2011,47(12):1391-1395
Li1 + x
Ti2 − x
Cr
x
(PO4)3 NASICON-type materials have been prepared and characterized by X-ray diffraction, scanning electron microscopy, and impedance
spectroscopy. The results demonstrate that Cr3+ doping increases the ionic conductivity of LiTi2(PO4)3 within the single-phase region of the doped material, which extends to x = 0.7. From temperature-dependent ionic conductivity data, the activation energy for lithium transport through interstitial
sites and the enthalpy of defect formation in LiTi2(PO4)3 are estimated at 30.0 ± 0.5 and 56 ± 1 kJ/mol, respectively. 相似文献
10.
Benjaram M. Reddy Gunugunuri K. Reddy Ibram Ganesh Jose M. F. Ferreira 《Journal of Materials Science》2009,44(11):2743-2751
Various CeO2
–M
x
O
y
(M
x
O
y
= SiO2, TiO2, ZrO2, and Al2O3) mixed oxides were prepared by microwave induced solution combustion method and analyzed by different complimentary techniques,
namely, X-ray diffraction (XRD), Raman spectroscopic (RS), UV–Vis diffuse reflectance spectroscopy (UV-DRS), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG-DTA), and BET surface area. XRD analyses revealed that CeO2
–SiO2 and CeO2
–TiO2 mixed oxides are in slightly amorphous form and exhibit only broad diffraction lines due to cubic fluorite structure of ceria.
XRD lines due to the formation of cubic Ce0.5Zr0.5O2 were observed in the case of CeO2
–ZrO2 sample. RS results suggested defective structure of the mixed oxides resulting in the formation of oxygen vacancies. The
UV-DRS measurements provided valid information about Ce4+ ← O2− and Ce3+ ← O2− charge transfer transitions. XPS studies revealed the presence of cerium in both Ce3+ and Ce4+ oxidation states. The ceria–zirconia combination exhibited better oxygen storage capacity (OSC) and CO oxidation activity
when compared to other samples. The significance of present synthesis method lays mostly on its simplicity, flexibility, and
the easy control of different experimental factors. 相似文献
11.
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
12.
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
13.
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
14.
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
15.
V. D. Parvanova S. K. Andreev 《Journal of Materials Science: Materials in Electronics》2005,16(5):249-252
By means of a solid-phase synthesis two types of microwave dielectric materials are obtained as follows: Ba1–xSrx(Zn1/3Ta2/3)0.94Ti0.06O3, where x = 0.20, 0.25, 0.30, 0.35 and 0.40 at sintering temperature TS = 1350, 1400 and 1450 C; Ba(Zn1/3Nb2/3)1–xZrxO3, where x = 0.04, 0.06, 0.08 and 0.10 at TS = 1300, 1350, and 1400 C. The microwave characteristics of the materials are investigated at f = 10 GHz. The composition Ba(Zn1/3Nb2/3)1–xZrxO3 demonstrates r = 38, Q = 6100 and f = +15 ppm C–1 and the composition Ba0.80Sr0.20- (Zn1/3Ta2/3)0.94Ti0.06O3 has r = 42, Q = 8200 and f = –13 ppm C–1. The composition Ba0.75Sr0.25(Zn1/3Ta2/3)0.94Ti0.06O3 has r = 40, Q = 6500 and low f = –13 C–1 ppm. This composition could be used successfully for realisation of dielectric microwave resonators for the satellite television. 相似文献
16.
The solubility of Nd at the Ba sites and the superconductivity of YBa2–x
Nd
x
Cu3O
y
were investigated by X-ray powder diffraction and measurements of the electrical resistance and ac susceptibility. The single Re123 phase was obtained for x0.30. The onset transition temperature
is insensitive to the Nd content x in the region of x0.40. All are higher than 95 K. The zero resistance transition temperatures
, however, exhibits two-step variation with the increase of x. For x0.25,
are all above 92 K. The highest
of 94 K was obtained for x=0.25. For x0.3
drops sharply to about 84 K. Finally
falls to 30 K and
is below 10 K for x=0.5. The two-step variation of T
c might be an indication of the existence of two trap levels for holes. 相似文献
17.
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
18.
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
19.
A. A. Pandit A. R. Shitre D. R. Shengule K. M. Jadhav 《Journal of Materials Science》2005,40(2):423-428
Ferrites with the general formula Mg1+xMnxFe2–2xO4(where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were prepared by the standard ceramic technique and studied by means of X-ray diffraction, magnetization, a.c. susceptibility and dielectric constant measurements. The X-ray analysis confirmed the single-phase formation of the samples. The lattice parameter is found to increase up to x = 0.3 and thereafter it decreases as x increases. The cation distribution has been studied by X-ray analysis and magnetization. Magnetization results exhibit collinear ferrimagnetic structure for x 0.3 and thereafter structure changes into non-collinear for x > 0.3. Curie temperature (TC) obtained from a.c. susceptibility data decreases with increasing x. The dielectric constant (), loss tangent (tan ) show strong frequency dependence. 相似文献
20.
A. P. Litvinchuk C. Thomsen M. Cardona L. Börjesson M. Käll P. Berastegui L. -G. Johansson 《Journal of Superconductivity》1994,7(1):113-116
We report a reflectivity study of thez-polarized TO-phonons of Pr
x
Y1–x
Ba2Cu4O8 and YBa2–y
Sr
y
Cu4O8 alloys in the temperature range 10–300 K. Anomalies of the frequency and linewidth of the plane-oxygen vibration at300 cm–1 due to the opening of the superconducting gap are found to occur upon crossing the superconducting transition temperatureT
c
. Phonon self-energy effects are strongly dependent onT
c
, providing evidence for a relative shift of the gap with respect to the energy of phonon.On leave from the Institute for Semiconductor Physics, Ukrainian Academy of Sciences, 252650 Kiev-28, Ukraine. 相似文献
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