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1.
A. Caneiro L. Mogni N. Grunbaum F. Prado 《Journal of Thermal Analysis and Calorimetry》2011,103(2):597-606
One of the most important challenges with solid oxide fuel cells (SOFC) is to find cathode materials with high enough catalytic
activity for the dissociation of the molecular oxygen. Oxide mixed conductors with the perovskite structure (ABO3) and high Co content in the B site have been extensively studied to be used as cathode in SOFC. This is the second part of
a review of high temperature properties of two mixed conductors systems. The first part was focused on the n = 2 Sr3FeMO6+δ (M = Fe, Co, Ni) Rudlesdden Popper phases, while in this paper we discuss the thermodynamic and transport properties of the
perovskite solid solution Sr1−x
La
x
Fe0.2Co0.8O3−δ (0 ≤ x ≤ 0.4) in the temperature range 773 ≤ T ≤ 1173 K. In particular, the interest has been focused on the x = 0 sample, which exhibits large ionic conductivity values (σi ~1 S cm−1), but suffers a structural transformation from cubic to orthorhombic symmetry because the ordering of the oxygen vacancies
when the oxygen partial pressure decreases. Measurements of the oxygen chemical potential (
m\textO2 \mu_{{{\text{O}}_{2} }} ) as function of oxygen content and temperature, coupled with high temperature X-ray diffraction data, permitted us to broaden
the knowledge of the T–δ–p(O2) phase diagram for the x = 0 sample. In addition, we have investigated the effects of the La incorporation on the stability range of the cubic phases
of the Sr1−x
La
x
Fe0.2Co0.8O3−δ solid solution. 相似文献
2.
E. A. Filonova A. N. Petrov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(11):1832-1835
The homogeneity regions of Nd1 − x
Ba
x
MnO3 (0.0 ≤ x ≤ 0.25) and NdMn1 − y
Fe
y
O3 (0.0 ≤ y ≤ 1.0) orthorhombic solid solutions in air at 1373 K were determined. The region of the existence of Nd1 − x
Ba
x
Mn1 − y
Fe
y
O3 orthorhombic solid solutions in air at 1373 K was studied. A fragment of the phase diagram of the NdMnO3-BaMnO3-BaFeO2.5-NdFeO3 quasi-quaternary complex oxide system in air at 1373 K was suggested. The mechanothermal properties of Nd0.75Ba0.25MnO3, Nd0.8Ba0.2Mn0.9Fe0.1O3, Nd0.8Ba0.2Mn0.7Fe0.3O3, and Nd0.8Ba0.2Mn0.5Fe0.5O3 doped neodymium manganates were studied. 相似文献
3.
D. R. Mane D. D. Birajdar Swati Patil Sagar E. Shirsath R. H. Kadam 《Journal of Sol-Gel Science and Technology》2011,58(1):70-79
Cu0.7−
x
Co
x
Zn0.3Fe2O4 (0 ≤ x ≤ 0.5) nanoparticles are prepared by sol–gel auto combustion method, using copper nitrate, zinc nitrate, ferric nitrate,
cobalt nitrate, and citric acid as the starting materials. The process takes only a few minutes to obtain as-received Co-substituted
Cu–Zn ferrite powders. X-ray diffraction (XRD), vibrational sample magnetometer and thermo gravimetric analysis are utilized
in order to study the effect of variation in the Co substitution and its impact on particle size, lattice constant, density,
cation distribution and magnetic properties like magnetization, coercivity, remanent magnetization, ferritization temperature
and associated water content. Lattice parameter found to increase with increasing Co content, whereas X-ray density, bulk
density, particle size showed decreasing trend with the Co content. Cation distribution indicates that the Co and Cu ion show
preference towards octahedral [B] site, Zn occupy tetrahedral (A) site whereas Fe occupy both tetrahedral (A) and octahedral
[B] site. Redistribution of cations takes place for x > 0.3. Saturation magnetization (Ms) increases from 52.99 to 79.62 emu/g (x ≤ 0.3), for x > 0.3 Ms decreases with increase in Co content x. However, coercivity, magnetocrystalline anisotropy and remanent magnetization increases with the Co2+ substitution. 相似文献
4.
Xiangqian Shen Zhi Zhou Fuzhan Song Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2010,53(2):405-411
Nanocomposites of ferrite and ferroelectric phases are attractive functional ceramic materials. In this work, the nanocomposite
Ni1−x
Co
x
Fe2O4–BaTiO3(x = 0.2, 0.3, 0.4, 0.5) fibers with fine diameters of 3 ~ 7 μm and high aspect ratios were synthesized by the organic gel-thermal
decomposition process from the raw materials of citric acid and metal salts. The structure, thermal decomposition process
and morphologies of the gel precursors and the resultant fibers derived from thermal decomposition of the gel precursors were
characterized by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction
and scanning electron microscopy. The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer.
The nanocomposite fibers of ferrite Ni1−x
Co
x
Fe2O4 and perovskite BaTiO3 are formed at the calcination temperature of 900 °C for 2 h. The average grain sizes of Ni1−x
Co
x
Fe2O4 and BaTiO3 in the nanocomposite fibers increase from about 15 nm to approximately 67 nm with the increasing calcination temperatures
from 900 to 1,180 °C. The saturation magnetization of the nanocomposite Ni1−x
Co
x
Fe2O4–BaTiO3(x = 0.2, 0.3, 0.4, 0.5) fibers increases with the increase of grain sizes of Ni1−x
Co
x
Fe2O4 and Co content, while the coercivity reaches a maximum value at the single-domain size of about 65 nm of Ni0.5Co0.5Fe2O4 obtained at the calcination temperature of 1,100 °C. 相似文献
5.
Yu. S. Okhlupin M. V. Ananyev N. F. Uvarov Yu. N. Bespalko S. N. Pavlova V. A. Sadykov 《Russian Journal of Electrochemistry》2011,47(6):663-670
Full conductivity, diffusion and oxygen exchange processes in composites (100 − x)La0.8Sr0.2Fe0.7Ni0.3O3 − δ−xCe0.9Gd0.1O1.95 (x is the volume fraction, 0 ≤ x ≤ 71.1%) at 700°C over the oxygen partial pressure range from 0.2 to 3 × 10−3 atm are studied by the electrical conductivity relaxation method. The composites’ conductivity was shown to decrease monotonically
with the increasing of Ce0.9Gd0.1O1.95 fraction, while the oxygen chemical diffusion coefficient increased. The oxygen exchange constant is higher for the composites
than for the individual phases of La0.8Sr0.2Fe0.7Ni0.3O3 − δ and Ce0.9Gd0.1O1.95. Possible reason of the dependence of the parameters D
chem and k
chem on the temperature, oxygen pressure, and the composite composition is the effect of the interface on the oxygen transfer
processes. Most effective oxygen transfer occurs in the composites whose composition approaches La0.8Sr0.2Fe0.7Ni0.3O3 − δ-Ce0.9Gd0.1O1.95 (x = 71%). 相似文献
6.
L. F. da Silva M. I. B. Bernardi L. J. Q. Maia G. J. M. Frigo V. R. Mastelaro 《Journal of Thermal Analysis and Calorimetry》2009,97(1):173-177
This work reports on the synthesis of a SrTi1−x
Fe
x
O3 nanostructured compound (0.0 ≤ x ≤ 0.1) using a modified polymeric precursor method. The effect of the addition of iron on the thermal, structural and morphological
properties of the nanoparticles was investigated by FT-IR spectroscopy, X-ray diffraction, and field emission scanning electron
microscopy (FE-SEM). A thermogravimetric analysis indicated that the crystallization process preceded by three decomposition
steps. Differential thermal analysis experiments showed that decomposition occurred in a broad range of temperatures from
400 to 600 °C. It was observed that iron ions acted as catalysts, promoting rapid organic decomposition and phase formation
at a lower temperature than in SrTiO3. Moreover, the addition of iron decreased the crystallite size and increased the lattice parameter of the SrTi1−x
Fe
x
O3 structure. 相似文献
7.
We investigate effects of Co dopant concentration on the structure and low temperature Raman scattering properties in SrTi1−x
Co
x
O3 (x = 0.00, 0.10, 0.20, 0.30) nanoparticles prepared by sol–gel method. The dopant induced changes are studied by XRD, and Raman
scattering measurements. The results show an average particle size of about 20 nm depending on the Co content and the lattice
parameters decrease as increasing the Co content. In the Raman spectra, a broad structure in the region 100–500 cm−1 is almost absent and the peaks in the region 600–800 cm−1 show different weights with respect to SrTiO3, relating to structural changes. The anomalous change in the area ratio of Raman peaks as function of temperature suggests
a phase transition in our samples in the range of 110–130 K. These results indicate that the Co ion has replaced the site
of Ti in unit cell. This novel route also demonstrates the advantage of synthesizing the compound with low annealing temperature. 相似文献
8.
Thermal behavior of xGa2O3–(50 − x)PbO–50P2O5 (x = 0, 10, 20, and 30 mol.% Ga2O3) and xGa2O3–(70 − x)PbO–30P2O5 (x = 0, 10, 20, 30, and 40 mol.% Ga2O3) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of
PbO for Ga2O3 is accompanied by increasing glass-transition temperature (263 ≤ T
g/°C ≤ 535), deformation temperature (363 ≤ T
d/°C ≤ 672), crystallization temperature (396 ≤ T
c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K−1 ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K
H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga2O3. 相似文献
9.
Huang Yudai Qi Yanling Jia Dianzeng Wang Xingchao Guo Zaiping Cho Won Il 《Journal of Solid State Electrochemistry》2012,16(5):2011-2016
Li4Ti5O12−x
Cl
x
(0 ≤ x ≤ 0.3) compounds were synthesized successfully via high temperature solid-state reaction. X-ray diffraction and scanning
electron microscopy were used to characterize their structure and morphology. Cyclic voltammetry, electrochemical impedance
spectroscopy, and charge/discharge cycling performance tests were used to characterize their electrochemical properties. The
results showed that the Li4Ti5O12−x
Cl
x
(0 ≤ x ≤ 0.3) compounds were well-crystallized pure spinel phase and that the grain sizes of the samples were about 3–8 μm. The
Li4Ti5O11.8Cl0.2 sample presented the best discharge capacity among all the samples and showed better reversibility and higher cyclic stability
compared with pristine Li4Ti5O12. When the discharge rate was 0.5 C, the Li4Ti5O11.8Cl0.2 sample presented the superior discharge capacity of 148.7 mAh g−1, while that of the pristine Li4Ti5O12 was 129.8 mAh g−1; when the discharge rate was 2 C, the Li4Ti5O11.8Cl0.2 sample presented the discharge capacity of 120.7 mAh g−1, while that of the pristine Li4Ti5O12 was only 89.8 mAh g−1. 相似文献
10.
Formation of solid solution has been explored in the valence compensated perovskite oxide system Sr1−xLaxTi1−xFexO3 (x ≤ 0.50). XRD studies indicate the formation of solid solution for the whole range investigated. All the compositions synthesised
have cubic structure similar to undoped SrTiO3. Study of dielectric behaviour of these materials show that orientational polarisation and space charge polarisation contribute
significantly to it.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
11.
Synthesis, characterization, and electrical conductivity of new Aurivillius-type oxide-ion conductor
Niyazi A. S. Al-Areqi Ahlam Al-Alas Saba Beg 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(13):2334-2344
A new oxide-ion conductor of Aurivillius family with a general formula Bi2Al
x
V1 − x
O5.5 − x − δ; 0 ≤ x ≤ 0.20 (BIALVOX) was synthesized by the sol-gel citrate route. Powder X-ray diffraction and simultaneous thermogravimetric
and differential thermal analyses confirmed that the calcination of BIALVOX xerogels is fully completed at around 500°C after
three hours of thermal treatment. It has been found that the β-orthorhombic phase is stabilized with compositions x ≤ 0.07, whereas the stabilization of the γ′-phase takes place for x ≥ 0.10. AC impedance spectroscopic investigation suggested that the charge accumulation at grain boundaries is thermally
activated process. However, the maximum electrical conductivity (7.73 × 10−5 S cm−1) noticed for BIALVOX.13 at 300°C was attributed to the maximum vacancy concentration in the equatorial planes, responsible
for the ion diffusion through the structure. This has been further evidenced by the temperature dependence of dielectric permittivity. 相似文献
12.
Yasumori Atsuo Katsuyama Tomokazu Kameshima Yoshikazu Okada Kiyoshi 《Journal of Sol-Gel Science and Technology》2000,19(1-3):237-242
Composite materials which consist of ferro- or ferrimagnetic fine particles in a glass matrix are expected to have a large residual magnetization and coercive force because of their fine magnetic domain structure, and has potential for superior magneto-optical properties compared with single or polycrystalline materials. In this study, the sodium borosilicate (NBS) glass containing Bi-substituted yttrium iron garnet (Bi
x
Y3–x
Fe5O12: BiYIG) fine particles, which show a superior magneto-optical effect, was prepared by the sol-gel method. BiYIG fine particles were stable in NBS gel-glass matrix during densification because the sintering temperature (580°C) of NBS gel was low enough to avoid pyrolysis of BiYIG and the reaction between BiYIG fine particles and the matrix. The Faraday rotation angle spectrum of the composite after deducting the contribution of the NBS glass matrix was intermediate between the reported ones of YIG and Bi0.25YIG polycrystalline thin films. The change of the Faraday rotation angles of the composite with imposing magnetic field showed a hysteresis loop. It was in good agreement with that of the magnetization curve of the composite. 相似文献
13.
Various compositions (1−x)BaTiO3 + xPbF2 + xLiF were prepared, shaped to pellets then sintered at 900°C for 2 h in gold sealed tubes. The purity and the symmetry of the
obtained samples were checked by X-ray diffraction. A new solid solution with Ba1−x
Pb
x
(Ti1−x
Li
x
) O3−3x
F3x formula occurs in the composition range 0 ≤ x ≤ 0.20. SEM observations were performed on polished and fractured ceramics. The complex permittivity was measured as a function
of temperature (−120°C ≤ T ≤ 250°C) and frequency (50 Hz ≤ f ≤ 4 × 107 Hz). The dielectric performances are the best for ceramic Ba0.97Pb0.03(Ti0.97Li0.03)O2.91F0.09. The real component ε′, exhibits a maximum of approximately 7500 at the ferroelectric Curie temperature T
C
≈ -18°C, the dielectric losses tan δ value being 0.012. At room temperature, the relaxation frequency f
r
is around 40 MHz for this ceramic. This novel ferroelectric oxifluoride is a promising material for applications, in particular
in the field of Z5U multilayer capacitors.
相似文献
14.
Ma LiJing Shi BingJie Cui MeiSheng Wang LinHong Li DianQing Chen AiFan 《中国科学B辑(英文版)》2008,51(3):211-217
The catalysts of hexaaluminate (BaMnxAl12-xO19-δ , x = 1.0, 2.0, 3.0, 4.0) to be used in methane combustion have been successfully synthesized by co-precipitation method and supercritical drying. The crystalline structure and surface area of catalyst were characterized by X-ray diffraction (XRD) and nitrogen adsorption analysis of BET method. BET analysis revealed that the preparing and drying method proposed here provides stable materials with higher surface area of 51.4 m2/g in comparison to materials prepared using conventional ambient drying method for BaMnxAl12?xO19-δ calcined at 1200℃ under oxygen. XRD analysis indicated that formation of a pure single phase BaMnxAl12-xO19-δ occurred up to x = 3 in the case of Mn-substituted barium hexaaluminates. Incorporation of Mn in excess leads to BaAl2O4 phase formation. As far as the valence state of Manganese ions was concerned, the introduced Mn ions were either divalent or trivalent. The first Mn ions were introduced in the matrix essentially as Mn2 and only for BaMn3Al9O19-δ does manganese exist exclusively as Mn3 ; the higher the Mn concen- tration, the higher the proportion of Mn3 . Catalytic activity for methane combustion has been measured for Mn-substituted barium hexaaluminates, light-off temperature was observed in the 512-624℃ range. The highest activity was obtained for catalysts containing 3 Mn ions per unit cell, which reveals that the BaMnxAl12-xO19-δ catalyst was a promising methane combustion catalyst with high activity and good thermal stability. Temperature programmed reduction (TPR) under hydrogen has been used to correlate the catalytic activity with the amount of easily reducible species. 相似文献
15.
V. N. Krasil’nikov A. P. Shtin O. I. Gyrdasova E. V. Polyakov L. Yu. Buldakova M. Yu. Yanchenko V. M. Zainullina V. P. Zhukov 《Russian Journal of Inorganic Chemistry》2010,55(8):1184-1191
Ti1−x
V
x
O2−y
C
y
(0 ≤ x ≤ 0.10 and x = 0.50) whiskers having the anatase structure were synthesized via thermolysis of vanadium-doped titanium glycolate of composition
Ti1−x
V
x
(OCH2CH2O)2 (0 ≤ x ≤ 0.10 and x = 0.50). The starting reagents used to prepare Ti1−x
V
x
(OCH2CH2O)2 were mixtures of coprecipitated titanium and vanadyl hydroxides, which were heated in ethylene glycol at T ≤ 200°C: (1 − x)TiO(OH)2 + xVO(OH)2 + 2HOCH2CH2OH = Ti1−x
V
x
(OCH2CH2O)2 + 3H2O↑. Thermolysis of vanadium-doped titanium glycolate in various gas media over a wide range of temperatures is useful to prepare
titania samples doped with both vanadium and carbon to form a phase of the general composition Ti1 − x
V
x
O2 − y
C
y
whiskers prepared by thermolyzing Ti1 − x
V
x
(OCH2CH2O)2 in air at 450°C were found to have a high photocatalytic activity in hydroquinone oxidation in aqueous solutions irradiated
in the UV spectral range; the photocatalyst’s activity increases with increasing vanadium concentration. When hydroquinone
was irradiated in the blue, the maximal catalytic activity was discovered in a sample of composition Ti0.50V0.50O2−y
C
y
. Quantum-chemical calculations support experimental data that the double doping of titania (Ti1−x
V
x
O2−y
C
y
) enhances its photocatalytic activity compared to undoped anatase or anatase doped in one sublattice: Ti1−x
V
x
O2 and TiO2−y
C
y
. 相似文献
16.
Anna Maria Cardinale Daniele Macciò Adriana Saccone 《Journal of Thermal Analysis and Calorimetry》2012,108(2):817-823
The isothermal section at 500 °C of the Dy–Al–Si system was studied in the whole concentration range. The alloys were characterized
by X-ray powder diffraction, scanning electron microscopy and electron micro-probe analysis. A few samples were analysed by
differential thermal analysis. The following intermetallic compounds, some of them showing variable composition, were found:
DyAl2Si2 (τ1), hP5-CaAl2O2 structure type, Dy2Al3Si2 (τ2) mS14-Y2Al3Si2 structure type, Dy2Al1+x
Si2−x
(τ3), 0 ≤ x ≤ 0.25, oI10-W2CoB2 structure type and Dy6Al3Si (τ4), tI80-Tb6Al3Si structure type. A number of binary phases dissolve the third element forming ternary solid solutions: Dy(Al1−x
Si
x
)3, 0 ≤ x ≤ 0.5, hP16-Ni3Ti structure type, Dy(Al
x
Si1−x
)2, 0 ≤ x ≤ 0.1, oI12-GdSi2 structure type, Dy(Al
x
Si1−x
)1.67, 0 ≤ x ≤ 0.2, oI12-GdSi2 structure type, DyAl
x
Si1−x
, 0 ≤ x ≤ 0.2, oC8-CrB, and Dy5(Al
x
Si1−x
)3, 0 ≤ x ≤0.3, hP16-Mn5Si3 structure type. The melting point of Dy6Al3Si was determined. 相似文献
17.
We investigate effects of Fe dopant concentration on the structure, as well as low temperature Raman scattering and electrical
transport properties in SrTi1−x
Fe
x
O3 (x = 0.00, 0.10, 0.20, 0.30, 0.40) nanoparticles prepared by sol-gel method. The results show an average particle size of powder
is about 30 nm, and the lattice parameters decrease as increasing the Fe content. In the Raman spectra, a broad structure
in the region 200–500 cm−1 is almost absent and the peaks in the region 600–800 cm−1 show different weights with respect to SrTiO3, relating to structural changes with increasing dopant concentration in conjunction with increasing grain boundary contribution
to the impedance. The abrupt change in Raman peak position as function of temperature suggests a phase transition in our samples
in the range of 110–150 K. These results indicate that the Fe ion has replaced the site of Ti in unit cell. These results
also demonstrate the feasibility of synthesizing the compound with low annealing temperature. 相似文献
18.
T. V. Chong S. Kambe H. Kawaji T. Atake O. Ishii 《Journal of Thermal Analysis and Calorimetry》2008,92(2):425-429
In this study, GdBaSr(Cu3−x
M
x)O7−δ bulk samples (M=Zn and Ni; 0≤x≤0.1) were prepared via solid-state reaction. Specific heat measurement (measured with thermal relaxation technique using
PPMS) shows an obvious specific heat jump around the T
c for GdBaSrCu3O7−δ sample as observed in most of the high temperature superconductors. It shifts towards lower temperature with increasing of
both Zn and Ni doping contents, whose tendency is similar to the decreasing of T
c. Debye temperature, ΘD (derived from specific heat measurements) calculated at around 10 K is found to be directly proportional to the T
c. 相似文献
19.
A quaternary super-ion-conducting system, 20CdI2 − 80[xAg2O − y(0.7V2O5 − 0.3B2O3)] where 1 ≤ x/y ≤ 3, has been prepared by melt quenching technique. The electrical conductivity measured was the order of 10−4 S/cm at room temperature. The values of silver-ion transport number obtained by electromotive force technique are nearly
unity. The thermoelectric power and electrochemical studies were done on the CdI2–Ag2O–V2O5–B2O3 system. The discharge and polarization characteristics were examined for different cathodes to evaluate the utility of these
cells as power sources for low energy applications. 相似文献
20.
In this paper, LiCr
x
Fe
x
Mn2−2x
O4 (x = 0, 0.05, 0.1) electrode materials were prepared by sol–gel technique and characterized by X-ray diffraction (XRD) and transmission
electron microscopy or high-resolution transmission electron microscopy techniques. XRD results reveal that the Cr–Fe-co-doped
LiCr
x
Fe
x
Mn2−2x
O4 materials are phase-pure spinels. The electrochemical properties of the LiMn2O4, LiCr0.05Fe0.05Mn1.9O4, and LiCr0.1Fe0.1Mn1.8O4 electrodes in 5 M LiNO3 aqueous electrolyte were investigated using cyclic voltammetry, AC impedance, and galvanostatic charge/discharge methods.
In the current range of 0.5–2 A g−1, the specific capacity of the LiCr0.05Fe0.05Mn1.9O4 electrode is close to that of the LiMn2O4 electrode, but the specific capacity of the LiCr0.1Fe0.1Mn1.8O4 electrode is obviously lower than that of the LiMn2O4 electrode. When the electrodes are charge/discharge-cycled at the high current rate of 2 A g−1, the LiCr0.05Fe0.05Mn1.9O4 electrode exhibits an initial specific capacity close to that of the LiMn2O4 electrode, but its cycling stability is obviously prior to that of the LiMn2O4 electrode. 相似文献