共查询到20条相似文献,搜索用时 31 毫秒
1.
N. A. Kochetova I. E. Animitsa A. Ya. Neiman 《Russian Journal of Electrochemistry》2010,46(2):168-174
Conductivity of the Sr6 − 2x
Ta2 + 2x
O11 + 3x
(0 ≤ x ≤ 0.33) solid solutions with the cryolite structure was studied in the atmosphere with a high content of water vapors under
temperature and oxygen activity variation in the gas phase. Appearance of the protonic conductivity component was proved at
the temperatures below 700°C. It was found that protonic conductivity increases at a decrease in parameter x in the composition series, which is due to an increase of both the concentration of protonic defects formed in the structure
and of their mobility. In the case of compositions with x < 0.15 at the temperatures below 550°C, the protonic transport becomes predominant. 相似文献
2.
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
3.
E. Kh. Kurumchin M. V. Ananyev D. I. Bronin G. K. Vdovin D. A. Osinkin 《Russian Journal of Electrochemistry》2010,46(7):774-779
The method of isotopic exchange was used to study the oxygen exchange kinetics in the oxides of La0.88Sr0.12Ga0.82Mg0.18O3 − δ and La0.80Sr0.20Ga0.85−x
Mg0.15Co
x
O3 − δ (x = 0.05, 0.15, 0.20, 0.25). The rates of oxygen exchange and its diffusion coefficients were determined in the temperature
range of 600–900°C at the oxygen pressure of 5 torr. The fractions of the three exchange types for the oxides studied were
determined at the temperature of 817°C and oxygen pressure of 5 torr. The total conductivity of the oxides of La0.80Sr0.20Ga0.85−x
Mg0.15Co
x
O3 − δ (x = 0.05, 0.15, 0.20, 0.25) was measured in the temperature range of 550–850°C in air and at the temperature of 800°C in the
range of oxygen pressures of 1–760 torr. It was shown that an increase in the electronic conductivity component due to an
increase in the cobalt fraction in the gallium sublattice results in growing interfacial exchange rate, total conductivity
of the studied systems, and a decrease in the effective conductivity activation energy. 相似文献
4.
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
5.
Yu. V. Danilov A. D. Neuimin L. A. Dunyushkina L. A. Kuzmina N. S. Zybko Z. S. Martemyanova A. A. Pankratov 《Russian Journal of Electrochemistry》2007,43(1):56-63
Phase composition, electroconductivity, oxygen ion transport number, and microhardness of samples of Ln1 − x
SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ (Ln = La, Pr, Nd; x, y = 0.10, 0.15) synthesized by a ceramic methods are studied. Methods of x-ray diffraction analysis and scanning electron microscopy
reveal the La-containing samples to be homogeneous and have a perovskite structure. Magnesium does not dissolve in Pr-and
Nd-containing systems but forms an individual phase based on magnesium oxide. Apart from magnesium oxide, in these systems
there form extrinsic phases, specifically, LnSrGa3O7 and an unknown phase. The electroconductivity of La1 − x
SrxGa1 − y
MgyO3 − δ decreases after substituting Al for Ga. Ceramic La1 − x
SrxGa0.5 − y/2Al0.5 − y/2MgyO3−δ is a purely ionic conductor in the temperature interval 500 to 1000°C; NdxSrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ has predominantly ionic conduction; and the predominant type of conduction in Pr1 − x
SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ is electronic below 700–800°C, with the contribution of ionic conduction increasing at higher temperatures. Substituting
Al for Ga raises the hardness of ceramics under study. Among the compositions studied, La0.85Sr0.15Ga0.45Al0.45Mg0.10O3 − δ and La0.85Sr0.15Ga0.425Al0.425Mg0.15O3 − δ exhibit a combination of electroconductivity and hardness that is optimal for application as electrolyte at reduced temperatures
(600–800°C). The Pr1 − x
SrxGa0.5 − y/2Al0.5 − y/2MgyO3 − δ system possesses mixed ionic-electronic conduction and high hardness, which makes it appealing for application as oxygen-penetrable
membranes.
Original Russian Text ? Yu.V. Danilov, A.D. Neuimin, L.A. Dunyushkina, L.A. Kuz’mina, N.S. Zybko, Z.S. Martem’yanova, A.A.
Pankratov, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 1, pp. 57–65. 相似文献
6.
Animitsa I. E. Neiman A. Ya. Sharafutdinov A. R. Kazakova M. G. 《Russian Journal of Electrochemistry》2001,37(3):266-272
The interaction of perovskite-like solid solutions Sr6 – 2x
Ta2 + 2x
O11 + 3x
(x= 0–0.28) with water is studied, along with dependences of the solutions' conductivity on their composition and the atmosphere's temperature and humidity. The Sr6 – 2x
Ta2 + 2x
O11 + 3x
phases with high concentrations of structural oxygen vacancies are high-temperature mixed oxygen–hydrogen ionic conductors whose conduction is sensitive to the presence of water vapor up to 900°C. According to a thermogravimetric study, the amount of water incorporated into the complex-oxide matrix is proportional to the concentration of structural oxygen vacancies. The process of water incorporation is considered in terms of crystalline and chemical properties of the structure. The oxygen-deficient perovskites containing coordination-unsaturated metalatoms can reconstruct their coordination polyhedron by adding water molecules, with subsequent partial dissociation of water to hydroxyl groups. The proposed mechanism explains different states of water in the oxide and a two-stage nature of its removal: water molecules coordinating the metal atom and those surrounding OH–leave the core in the first and second stages, respectively. 相似文献
7.
La0.8Sr0.2Ga0.85-x
Mg0.15Co
x
O3±δ-materials (further cobalt-doped LSGM), where x varied from 0 to 0.20, were synthesized by means of the conventional powder route. The total conductivity of the La0.8Sr0.2Ga0.85-x
Mg0.15Co
x
O3±δ samples was measured as a function of temperature (400–900 °C) and oxygen partial pressure
by means of the impedance technique. The values of the oxygen ionic and the hole conductivities were determined from non-linear regression of the oxygen partial pressure dependence of the total conductivity. It was shown that the substitution of gallium by cobalt in the LSGM results in increasing either the oxygen ionic or the hole conductivity, although the increase of the hole conductivity due to the doping by cobalt is more significant than the increase of the oxygen ionic conductivity. The hole conductivity of the selected compositions was studied by oxygen permeation- and Hebb–Wagner-polarization measurements. 相似文献
8.
A. Yu. Suntsov I. A. Leonidov A. A. Markov M. V. Patrakeev Ya. N. Blinovskov V. L. Kozhevnikov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(5):832-838
The special features of the structure, electrophysical properties, and oxygen nonstoichiometry of new double perovskites PrBaCo2 − x
Cu
x
O5 + δ were studied. Within the homogeneity region with respect to copper 0 < x ≤ 1, solid solution samples had an orthorhombic structure (space group Pmmm) with the parameters a
p
× 2a
p
× 2a
p
, where a
p
≈ 3.8 ?. The oxygen nonstoichiometry of PrBaCo2 − x
Cu
x
O5 + δ changes as the copper content increases approximately as δ ≈ 0.85 − x/2. The content of oxygen was measured by coulometric titration over wide temperature and oxygen pressure ranges. The partial
thermodynamic functions of labile oxygen were calculated and the limits of the thermodynamic stability of the solid solution
were established.
Original Russian Text ? A.Yu. Suntsov, I.A. Leonidov, A.A. Markov, M.V. Patrakeev, Ya.N. Blinovskov, V.L. Kozhevnikov, 2009,
published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 954–960. 相似文献
9.
E. A. Filonova A. N. Demina A. N. Petrov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(10):1591-1594
The formation of the orthorhombic solid solution series LaMn1−y
Ti
y
O3 with 0.0 ≤ y ≤ 0.15 and LaMn1−y
Ni
y
O3 with 0.0 ≤ y ≤ 0.4 was observed. The stability boundaries of the La1−x
Sr
x
Mn1−y
M
y
O3 (M = Ti, Ni) perovskite phases were determined. Fragments of isobaric-isothermal sections of the phase diagrams of the La2O3-SrO-Mn3O4-TiO2 and La2O3-SrO-Mn3O4-NiO systems in air at 1100°C were suggested.
Original Russian Text ? E.A. Filonova, A.N. Demina, A.N. Petrov, 2007, published in Zhurnal Fizicheskoi Khimii, 2007, Vol.
81, No. 10, pp. 1787–1790. 相似文献
10.
E. Yu. Pikalova A. A. Murashkina D. A. Medvedev 《Russian Journal of Electrochemistry》2011,47(6):681-689
CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical
devices. This work presents the results of systematic studies of structural and electric properties and oxygen nonstoichiometry
of the Ce0.8(Sm1 − x
Ca
x
)0.2O2 − δ system in a wide range of concentrations of 0 < x < 1 performed in order to establish the causes affecting the system conductivity and its behavior in a reducing medium. It
is found that a single-phase solid solution of the fluorite type is formed in the whole concentration range. Parameters of
its lattice cells decrease linearly at an increase in the concentration of Ca2+. Conductivity in air grows when calcium is added due to a decrease in the grain boundary resistance. The maximum conductivity
in air was obtained for the composition of Ce0.8(Sm0.8Ca0.2)0.2O2 − δ and is 13.71 × 10−3 S/cm at 873 K. Studies of the dependence of conductivity of the partial pressure of oxygen showed that electron conductivity
is observed at a higher oxygen partial pressure at an increase in the temperature and calcium concentration. The critical
partial pressure of oxygen ( pO2 * )\left( {p_{O_2 }^* } \right) for the compositions of Ce0.8(Sm1 − x
Ca
x
)0.2O2 − δ with x = 0; 0.2, and 0.5 is 1.83 × 10−16, 1.73 × 10−13, and 3.63 × 10−13 atm at 1173 K, respectively, and 2.76 × 10−21, 5.05 × 10−18, and 1.31 × 10−18 atm at 1023 K. 相似文献
11.
I. A. Zvereva A. G. Cherepova Yu. E. Smirnov 《Russian Journal of General Chemistry》2007,77(4):517-523
The area of existence of Gd2Sr1−x
Ca
x
Al2O7 solid solutions at x ≤ 0.5 was determined by the X-ray phase analysis. It was found by full-profile X-ray structural analysis that, in contrast
to La2Sr1−x
Ca
x
Al2O7 solid solutions, the Ca2+ cations occupy not only AO9 nine-vertex fragments, but also AO12 oxygen cubooctahedra. Full ordering of Sr2+ cations in the perovskite layer is observed at the calcium content x 0.5.
Original Russian Text ? I.A. Zvereva, A.G. Cherepova, Yu.E. Smirnov, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol.
77, No. 4, pp. 557–563.
For communication XI, see [1]. 相似文献
12.
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
13.
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
14.
Vibe L. E. Simonsen Linda Nørskov Kent Kammer Hansen 《Journal of Solid State Electrochemistry》2008,12(12):1573-1577
A series of La2 − x
Sr
x
CuO4 (x = 0.0, 0.05, 0.15, 0.25 and 0.35) compounds was investigated for the use of direct electrochemical reduction of NO in an
all-solid-state electrochemical cell. The materials were investigated using cyclic voltammetry in 1% NO in Ar and 10% O2 in Ar. The most selective electrode material was La2CuO4, which had an activity of NO reduction that was 6.8 times higher than that of O2 at 400 °C. With increasing temperature, activity increased while selectivity decreased. Additionally, conductivity measurements
were carried out, and the materials show metallic conductivity behavior which follows an adiabatic small polaron hopping mechanism. 相似文献
15.
V. A. Prituzhalov E. I. Ardashnikova V. A. Dolgikh A. M. Abakumov 《Russian Journal of Inorganic Chemistry》2011,56(3):313-324
Tysonite solid solutions Bi1−x
Ba
x
O
y
F3−x−2y
in the BiF3-BiOF-BaF2 system were obtained by solid-phase synthesis in sealed copper tubes in an argon atmosphere at 873 K with subsequent quenching.
The solid solutions were studied by X-ray diffraction, electron diffraction, and impedance spectroscopy. On the basis of X-ray
powder diffraction data, the homogeneity ranges of the tysonite solid solutions were determined and the scheme of their location
in the BiF3-BiOF-BaF2 system at 873 K was suggested. Aliovalent substitutions in both the cation and anion sublattices Ba2+ → Bi3+ and O2− → F− made it possible to vary the concentration of anion vacancies. It was found that, at a high concentration of anion defects
at 873 K, the hexagonal tysonite modification with space group P63/mmc is stable. With a decrease in the defect concentration, the trigonal tysonite modification with space group $
P\bar 3c1
$
P\bar 3c1
becomes stable. An ordered monoclinic tysonite-type modification BiO
y
F3 − 2y
(0.13 < y < 0.23) was revealed. For the homogeneity ranges of all tysonite phases, dependences of the unit cell parameters and conductivity
on the composition along the sections with a constant barium or oxygen content were reported. The most probable location of
oxygen anions and anion vacancies in the tysonite structure is discussed. 相似文献
16.
M. V. Ananyev E. Kh. Kurumchin N. M. Porotnikova 《Russian Journal of Electrochemistry》2010,46(7):789-797
The method of isotopic exchange was used to study the kinetics of oxygen exchange and diffusion in complex oxides of La1 − x
Sr
x
Co1 − y
Fe
y
O3 − δ (x = 0.0, y = 0.0; x = 0.6, y = 0.2, 0.4). The rates of oxygen interfacial exchange and its diffusion coefficient were determined for LaCoO3 − δ at the pressure of 5 torr in the temperature range of 600–850°C and at the temperature of 700°C in the pressure range of
1–70 torr. The contributions of the three exchange types were calculated. The order of the dependence of the interfacial exchange
rate on the oxygen pressure was 0.51 ± 0.01. In the case of La0.4Sr0.6Co1 − y
Fe
y
O3 − δ (y = 0.2, 0.4) in the temperature range of 600–900°C at the oxygen pressure of 10 torr, the oxygen exchange rates and diffusion
coefficients were determined in the material bulk and in the subsurface region; contributions of the three types of exchange
were calculated. The paper considers the mechanism of oxygen exchange and diffusion as compared to nonstoichiometry in the
oxygen sublattice of the La1 − x
Sr
x
Co1 − y
Fe
y
O3 − δ oxides. 相似文献
17.
M. I. Pantyukhina A. L. Podkorytov V. M. Zhukovskii 《Russian Journal of Inorganic Chemistry》2010,55(1):103-111
Homogeneous fields of Sr4 − x
M
x
Nb2O9 (M = Cd, Cu, Ni, or Zn) solid solutions were determined using powder X-ray diffraction. Phase fields were plotted proceeding
from the tolerance factor t and electronegativity ratio $
\bar k_A /\bar k_B
$
\bar k_A /\bar k_B
with a satisfactory fit of experimental results. Thermogravimetry was used to establish the major kinetic laws of solid-phase
synthesis (conversion, rate-controlling stage, and effective activation energy) in (4 − x)SrCO3 + xMO + Nb2O5 powdery mixtures. Direct radiometry was used to determine 90Sr, 63Ni, and 65Zn self-diffusion coefficients in solid solutions based on the Sr4Nb2O9 phase. Electrical conductivity was measured as a function of temperature for all Sr4Nb2O9-“M4Nb2O9” samples. The conductivity of Sr4 − x
M
x
Nb2O9 (M = Cd, Cu, Ni, or Zn) solid solutions has a mixed ion-electron character. 相似文献
18.
The phase and chemical compositions of the precipitates forming in the Sr(VO3)2-VOCl2-H2O system in the V4+/V5+ = 0.11–9 range at 80–90°C are reported. At pH 1–3 and V4+/V5+ = 0.25−9, the general formula of the precipitated compounds is Sr
x
V
y
4+ V12−y
5+O31−δ·nH2)(0.37 ≤ x ≤ 1.0, 1.7 ≤ y ≤ 3.0, 0.95 ≤ δ ≤ 2.1). Polyvanadates containing the largest amount of vanadium(IV) are obtained at an initial V4+/V5+ ratio of 9 and pH 1.9. Precipitation from solutions at pH 3 takes place only in the presence of the VO2+ ion, and the highest precipitation rate is observed at V4+/V5+ = 0.11. The process is controlled by a second-order reaction on the polyvanadate surface. Under hydrothermal conditions at
180°C, Sr0.25V2O5·1.5H2O nanorods are obtained from solutions with a V4+/V5+ molar ratio of 0.1 at pH 3. The nanorods, 30–100 nm in diameter and up to 2–3 μm in length, have a layered structure with
an interlayer spacing of 10.53 ± 0.08 ?. 相似文献
19.
V. D. Zhuravlev V. G. Zubkov A. P. Tyutyunnik Yu. A. Velikodnyi N. D. Koryakin 《Russian Journal of Inorganic Chemistry》2009,54(1):134-136
The phase compositions of theLaVO4-SrMoO4(1) and Sr2GeO4-SrMoO4 (2) binary systems, which bound the Sr2GeO4-LaVO4-SrMoO4 (3) ternary system, and the LaSr2(VO4)(GeO4)-Sr2GeO4+SrMoO4 section (4) of system 3 are studied at subsolidus temperatures. Systems 1 and 2 consist of a mixture of the initial compounds,
and the La1 − x
Sr2 + x
(GeO4)(V1 − x
Mo
x
O4) (where 0 ≤ x ≤ 0.4) region of substitutional solid solutions with a palmierite structure is formed in system 3. The unit cell parameters
of the solid solutions are determined. The distribution of the lanthanum and strontium cations over two positions of the cationic
sublattice is described.
Original Russian Text ? V.D. Zhuravlev, V.G. Zubkov, A.P. Tyutyunnik, Yu.A. Velikodnyi, N.D. Koryakin, 2009, published in
Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 135–137. 相似文献
20.
V. P. Gorelov V. B. Balakireva A. V. Kuz’min 《Russian Journal of Electrochemistry》2010,46(8):890-895
Ionic, proton, and oxygen conductivities are measured as functions of air humidity (pH2O = 0.04−3.57 kPa) in the BaZr1 − x
Y
x
O3 − α system (x = 0.02−0.15) over the temperature range 600–900°C. The important result is obtained that dissolved water vapor determines
not only proton transport, but also the overwhelming part of oxygen transport in BaZr1 − x
Y
x
O3 − α. 相似文献