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1.
M. Barré F. Le Berre M-P. Crosnier-Lopez C. Galven O. Bohnké J-L. Fourquet 《Ionics》2009,15(6):681-687
The Li1−x
La
x
/3Zr2(PO4)3 NASICON-type compounds (0 ≤ x ≤ 1) have been synthesized in powder form by a sol-gel method and sintered for ionic conductivity measurements. In order
to improve the compactness of the ceramic without decomposition of the compound, several sintering processes have been tested
for one member of the solid solution (x = 0.6): the use of sintering aids (ZnO, B2O3, TiO2 and LiNO3), a ball-milling of the synthesized powder, a flash heating, high isostatic pressure, and spark plasma sintering. Finally,
a satisfactory compactness of 85% is obtained compared to the referenced value (63%) obtained by uniaxial and isostatic pressing.
The ionic conductivity study was performed by impedance spectroscopy. It shows that, despite the formation of vacancies, the
substitution Li+→ 1/3 La3+ + 2/3 □ has unfortunately no influence on the conduction for 0 ≤ x ≤ 0.7 since the ionic conductivity remains identical to the LiZr2(PO4)3 one. For higher x values, the ionic conductivity strongly decreases. 相似文献
2.
Solid solutions of (CsHSO4)1 − x(CsH2PO4)x (x = 0.25-0.75) were synthesized by mechanical milling method over a wide range of compositions. Superprotonic cubic phase was confirmed for all these samples between 293 and 420 K depending on its composition. These superprotonic phases have primitive cubic structure similar to that of CsH2PO4. The kinetic stability of the supercooled cubic phase depends both on the composition x and the humidity of surrounding atmosphere. The most stable composition of the cubic phase was found around x = 0.67 and could be maintained for several days even under ambient atmosphere. The ionic conductivities of these superprotonic phases reached 10− 2–10− 3 S∙cm− 1 at 450 K. With increasing x the ionic conductivity at the superprotonic phase decreased continuously associated with the increase of the activation energy. These findings suggest that the average number of the hydrogen bonds between XO4 (X = S, P) units plays an important role on the stability of the cubic phase and also on the conductivity. 相似文献
3.
Multiple ion-doped lithium manganese oxides LiCrxNixMn2-2xO4-zFz (0 < x ≤ 0.25, z = 0.05, 0.1) with a spinel structure and space group Fd m were prepared by using the co-precipitation procedure carried out in water–alcohol solvent using adipic acid as the chelating
agent. The electrochemical measurements indicated that the charge/discharge capacities of the samples prepared at 600 °C are
higher than that of the treatment at 800 °C or microwave heating. The capacitance-voltage (CV) curves of LiCrxNixMn2-2xO4-zFz (0 < x ≤ 0.25, z = 0.05, 0.1) showed that when x ≤ 0.1, the samples had two reduction–oxidation peaks at 4.0 to 4.2-V region, whereas when x > 0.1, the samples had only one reduction–oxidation peak at 4.0- to 4.2-V region in CV measurements and could offer more
stable voltage plateau in a 4-V region and also had stable electrical conductivity after 20 cycles. Another reduction–oxidation
peak appeared in 4.6-4.8-V region (Ni2+–Ni4+ reduction–oxidation peaks); this suggests that the LiCrxNixMn2-2xO4-zFz (0.1 < x≤ 0.25, z = 0.05, 0.1) cathode material could offer 4.6 to 4.8-V charge/discharge plateaus, and its specific capacity increases with
increasing Ni2+. The impedance measurements of the cell proved that the F− anion doped can not only prevent Mn3+ from disproportion but also can prevent the passivation film from forming and can help keep stable the cell’s electrical
properties. The LiCr0.05Ni0.05Mn1.9O3.9F0.1 sintered at 600 °C shows the best cycle performance and the largest capacity in all prepared samples; its first discharge
capacity is 120 mAh/g, and the discharge capacity loses only 1.78% after 20 cycles. After 100 cycles, it still remains in
the spinel structure. 相似文献
4.
A new proton-conductive membrane (PCM) based on poly (vinyl alcohol) and ammonium sulfate (NH4)2SO4 complexed with sulfuric acid and plasticized with ethylene carbonate (EC) at different weight percent were prepared by casting
technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD patterns of all the
prepared polymer electrolytes reveal the amorphous nature of the films. ac conductivity and dielectric spectra of the electrolyte
were studied with changing EC content from weight 0.00 to 0.75 g. A maximum conductivity of 7.3 × 10−5 S cm−1 has been achieved at ambient temperature for PCM containing 0.25 g of ethylene carbonate. The electrical conductivity σ, dielectric constant ε′ and dielectric loss ε″ of PCM in frequency range (100 Hz to 100 KHz), and temperature range (300–400 K) were carried out. Measurement of transference
number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization
technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due
to ions. The electrolyte with the highest electrical conductivity was used in the fabrication of a solid-state electrochemical
cell with the configuration (Mg/PCM/PbO2). Various cell parameters ldensity, and current density were determined. The fabricated cells gave capacity of 650 μAh and
have an internal resistance of 11.6 kΩ. 相似文献
5.
The present paper reports the reactivity between TiO2 and oxygen and the related charge transfer at 298 and 1,073 K. The studies were performed using work function measurements. It was found that oxidation of TiO2 at 1,073 K and p(O2) = 75 kPa, initially standardized at 1,173 K and p(O2) = 10 Pa, results in work function changes that are consistent with the theoretical model of the charge transfer during oxygen chemisorption and oxygen incorporation at the absence of structural transitions. However, oxidation of TiO2 at 298 K, p(O2) = 75 kPa, which has been initially standardized at 1,173 K in extremely reducing conditions at p(O2) = ∼10−10 Pa, results in work function changes that are consistent with low-dimensional structural changes of the surface layer. It is shown that oxidation of strongly reduced TiO2 at 298 K results in a decrease of work function, which cannot be explained without assuming the structural changes of the outermost surface layer. 相似文献
6.
Bi4V2O11 exists in three phases viz. α, β, and γ. High temperature γ-phase can be stabilized to room temperature owing to its higher
conductivity by the partial substitution of metallic cations for vanadium in Bi4V2O11. Phase transitions from α → β and β → γ are composition and temperature-dependent. Mn2+-doped compounds Bi4V2−x
Mn
x
O11−
δ
(0 ≤ x ≤ 0.4) have been synthesized by solid state reaction technique and investigated by X-ray diffraction and ionic conductivity
measurement. High ionic conducting γ-phase is stabilized for x ≥ 0.2. The ionic conductivity of the series of Bi4V2−x
Mn
x
O11−
δ
samples has been measured by using ac impedance spectroscopy technique. The conductivity data do show departure from its
simple Arrhenius behavior for all of the compositions. The highest conductivity observed for x = 0.2 sample can be attributed to lower activation energy. 相似文献
7.
The positive muon spin relaxation method is applied to probe magnetic ordering in the superconducting phase of a high quality
single crystal of La2−xSrxCuO4−σ (0.11≤x≤0.14). The well characterized crystal ofx=0.11 (T
c=34.5 K) with nearly complete flux exclusion exhibits spin freezing at 8K(T
f) with significant spin fluctuation up to 20 K. The onset of spin fluctuation andT
f decrease against increasingx towardsx=0.15, suggesting an existence of a magnetic phase boundary aroundx whereT
c becomes maximum. 相似文献
8.
W. J. Kossler X. H. Yu A. Greer H. E. Schone C. E. Stronach M. Davis R. S. Cary W. F. Lankford A. Moodenbaugh J. Oostens 《Hyperfine Interactions》1991,63(1-4):253-258
Transverse-and zero-field μSR measurements have been made for YBa2(Cu1−x
Fe
x
)3O7 withx=0.04, 0.08 and 0.12. The temperature range studied was from approximately 7.5 K to 100 K. The onset of magnetic ordering
commences at about 7.5 K forx=0.04, 10 K forx=0.08 and 20 K forx=0.12. The Gaussian depolarization parameter, σ ofG
x
(t) = exp(−σ2
t
2/2), is depressed by a factor of about 0.6 forx=0.04, but for thex=0.08 sample σ is depressed by a factor of 10 and increasing suppression is seen as the temperature is lowered below 45 K.
This decrease in σ is interpreted in terms of decreasing electronic mean free paths. 相似文献
9.
Here we report the synthesis, chemical stability, and electrical conductivity of Ti-doped perovskite-type BaCe0.8-x
Ti
x
Y0.2O3-δ
(x = 0.05, 0.1, 0.2, and 0.3; BCTY). Samples were synthesized by conventional solid state (ceramic) reaction from corresponding
metal salts and oxides at elevated temperature of 1,300–1,500 °C in air. The powder X-ray diffraction confirmed the formation
of a simple cubic perovskite-type structure with a lattice constant of a = 4.374(1), 4.377(1), and 4.332(1) ? for x = 0.05, 0.1, and 0.2 members of BCTY, respectively. Like BaCe0.8Y0.2O3-δ
(BCY), Ti substituted BCTY was found to be chemically not stable in 100% CO2 and form BaCO3 at elevated temperature. The bulk electrical conductivity of BCTY decreased with increasing Ti content and the x = 0.05 member exhibited the highest conductivity of 2.3 × 10−3 S cm−1 at 650 °C in air, while a slight increase in the conductivity, especially at low temperatures (below 600 °C), was observed
in humidified atmospheres. 相似文献
10.
B. Sitamtze Youmbi Serge Zékeng Samuel Domngang Florent Calvayrac Alain Bulou 《Ionics》2012,18(4):371-377
To date, the fastest lithium ion-conducting solid electrolytes known are the perovskite-type ABO3 oxide, with A = Li, La and B = Ti, lithium lanthanum titanate (LLTO)
Li3x La( 2 \mathord