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1.
Cubic-stabilized ((DyO1.5) x –(WO3) y –(BiO1.5)1 − x − y ) electrolytes (DWSB) with much higher conductivity than (ErO1.5)0.2(BiO1.5)0.8, 20ESB, were developed through a double-doping strategy. (DyO1.5)0.08–(WO3)0.04–(BiO1.5)0.88, 8D4WSB, is the highest conductivity composition but underwent the greatest conductivity degradation at 500 °C due to its low total dopant concentration. The effect of dopant composition on conductivity behavior with time at 500 °C demonstrates that there is a trade-off between initial conductivity and long-term stability at this temperature. Therefore, it is necessary to find an optimal total and relative concentration of dopants to provide the enhanced long-term stability needed to make this DWSB electrolyte system feasible for 500 °C operation. To this end, it was found that (DyO1.5)0.25–(WO3)0.05–(BiO1.5)0.70, 25D5WSB, maintained a conductivity of 0.0068 S/cm without appreciable degradation after annealing at 500 °C for 500 h. Moreover, since bismuth oxide-based electrolytes do not exhibit any grain boundary impedance, the total conductivity of 25D5WSB is significantly higher than that of alternate electrolytes (e.g., GDC: Gd0.1Ce0.9O1.95) at this temperature.  相似文献   

2.
This paper reports the heterogeneously doped alumina (Al2O3) on the ionic conductivity of thallium iodide. Composite materials of formula (1 − x) TlI–xAl2O3, x = 0–0.7 have been prepared and studied by X-ray diffraction, differential scanning calorimetry, and electrical conductivity. X-ray diffraction and differential scanning calorimetry proved the formation of composite in this binary system. The maximum enhancement observed is about three orders of magnitude with respect to the host material. The enhancement of electrical conductivity in comparison with pure thallium iodide can be interpreted with the space charge layer model. Moreover, the increased content of alumina in the system leads to the disappearance of phase transition β–α thallium iodide, which is usually observed in the pure compound. This behavior was explained by stabilizing effect of β-phase at high temperatures and suppression of α-phase at higher contents of alumina.  相似文献   

3.
Sr1−x La x Zn x Fe12−x O19/poly(vinylpyrrolidone) (PVP) (0.0≤x≤0.5) precursor nanofibers were prepared by the sol–gel assisted electrospinning method from starting reagents of metal salts and PVP. Subsequently, the Sr1−x La x Zn x Fe12−x O19 nanofibers with diameters of around 100 nm were obtained by calcination of the precursor at 800 to 1000°C for 2 h. The precursor and resultant Sr1−x La x Zn x Fe12−x O19 nanofibers were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer and vibrating sample magnetometer. The grain sizes of Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers are in a nanoscale from 40 to 48 nm corresponding to the calcination temperature from 800 to 1000°C. With La–Zn substitution content increase from 0 to 0.5, the grain size and lattice constants for the Sr1−x La x Zn x Fe12−x O19 nanofibers obtained at 900°C show a steady reduction trend. With variations of the ferrite particle size arising from the La–Zn substitution, the nanofiber morphology changes from the necklace-like structure linking by single elongated plate-like particles to the structure building of multi-particles on the nanofiber cross-section. The specific saturation magnetization of Sr1−x La x Zn x Fe12−x O19 nanofibers initially increases with the La–Zn content, reaching a maximum value 72 A m2 kg−1 at x=0.2, and then decreases with a further La–Zn content increase up to x=0.5, while the coercivity exhibits a continuous reduction from 413 (x=0) to 219 kA m−1 (x=0.5). The mechanism for the La–Zn substitution and the nanofiber magnetic property are analyzed.  相似文献   

4.
Composite materials used for electrode and electrolyte materials have been intensely studied in view of their advantages such as higher conductivity and better operational performance compared to their single-phase counterparts. The present work aims at studying the electrical and structural characteristics of a new composite electrolyte namely, (PbI2) x  − (Ag2O–Cr2O3)100−x where x = 5, 10, 15, 20, and 25 mol%, respectively, prepared by the melt quenching technique. The room temperature X-ray diffraction spectra revealed certain crystalline phases in the samples. AC conductivity analysis for all the prepared samples was carried out over the frequency range 1 MHz–20 Hz and in the temperature window 297–468 K. The room temperature conductivity values were calculated to be in the order of 10−5–10−3 Scm−1. An Arrhenius dependence of temperature with conductivity was observed, and the activation energies calculated were found to be in the range 0.27–0.31 eV. Furthermore, the total ionic transport number (t i) values obtained for all these indicated the ionic nature of this system. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.  相似文献   

5.
LiAl x Mn2 − x O4 and LiAl0.05Mn1.95O4 − y F y spinel have been successfully synthesized by citric acid-assisted sol–gel method. The structure and physicochemical properties of this as-prepared powder were investigated by electronic conductivity test, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge test in detail. The electronic conductivity decreases with increasing of the content of doped Al. XRD patterns show that the diffraction of LiAl0.05Mn1.95O4 − y F y samples is similar, with all the peaks indexable in the Fd3m space group, and a little impurity appears in the LiAl0.05Mn1.95O3.8F0.2 sample. SEM reveals that all LiAl0.05Mn1.95O4 − y F y powders have the uniform, nearly cubic structure morphology with narrow size distribution which is less than 500 nm. Galvanostatic charge–discharge test indicates that LiAl0.05Mn1.95O4 has the highest discharge capacity and electrochemical performance among all LiAl x Mn2 − x O4 samples after 50 cycles, and the initial discharge capacity of LiAl0.05Mn1.95O4 − y F y (y = 0, 0.02, 0.05, 0.1) is 123.9, 124.6, 124.9, and 125.0 mAh g−1, respectively, and their capacity retention ratios are 94.2%, 94.9%, 91.7%, and 89.9% after 50 cycles, respectively. EIS indicates that LiAl0.05Mn1.95O3.98F0.02 have smaller charge transfer resistance than that of LiAl0.05Mn1.95O4 corresponding to the extraction of Li+ ions.  相似文献   

6.
H. G?ktepe  H. ?ahan  ?. Patat  A. ülgen 《Ionics》2009,15(2):233-239
To improve the cycle performance of spinel LiMn2O4 as the cathode of 4-V-class lithium secondary batteries, spinel phases LiM x Mn2 − x O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M y Mn1.95 − y O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) were successfully prepared using the sol–gel method. The spinel materials were characterized by powder X-ray diffraction (XRD), elemental analysis, and scanning electron microscopy. All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. Electrochemical studies were carried out using the Li|LiM x Mn2 − x O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M y Mn1.95 − y O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) cells. These cathodes were more tolerant to repeated lithium extraction and insertion than a standard LiMn2O4 spinel electrode in spite of a small reduction in the initial capacity. The improvement in cycling performance is attributed to the stabilization in the spinel structure by the doped metal cations.  相似文献   

7.
The stoichiometry range and lithium ion conductivity of Li5+x Ba x La3−x Ta2O12 (x = 0, 0.25, 0.50, 1.00, 1.25, 1.50, 1.75, 2.00) with garnet-like structure were studied. The powder X-ray diffraction data of Li5+x Ba x La3−x Ta2O12 indicated that single phase oxides with garnet-like structure exist over the compositional range 0 ≤ x ≤ 1.25; while for x = 1.5, 1.75 and 2.00, the presence of second phase in addition to the major garnet like phase was observed. The cubic lattice parameter increases with increasing x and reaches a maximum at x = 1.25 then decreases slightly with further increase in x in Li5+x Ba x La3−x Ta2O12. The impedance plots of Li5+x Ba x La3−x Ta2O12 samples obtained at 33 °C indicated a minimum grain-boundary resistance (R gb) contribution to the total resistance (R b + R gb) at x = 1.0. The total (bulk + grain boundary) ionic conductivity increases with increasing lithium and barium content and reaches a maximum at x = 1.25 and then decreases with further increase in x in Li5+x Ba x La3−x Ta2O12. Scanning electron microscope investigations revealed that Li6.25Ba1.25La1.75Ta2O12 is much more dense, and the grains are more regular in shape. Among the investigated compounds, Li6.25Ba1.25La1.75Ta2O12 exhibits the highest total (bulk + grain boundary) and bulk ionic conductivity of 5.0 × 10−5 and 7.4 × 10−5 S/cm at 33 °C, respectively.  相似文献   

8.
The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag2O–16.67[(V2O5)1−x –(MoO3) x ] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly with glass former variation. However, the activation energies for structural relaxation (E s) at glass transition temperature and crystallization (E c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO3 substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first heating cycle at room temperature is found to be increasing with MoO3 content and maximum for x = 0.3 (~10−3 Ω−1 cm−1 at 30 °C) which is comparable to that of the host 50AgI–33.33Ag2O–16.67V2O5 glassy system. The parameters obtained from σT plots and DSC scans do complement each other in a particular range of composition.  相似文献   

9.
The Ba2In2 − x Sn x O5 + x/2 solid solution was confirmed up to x = 1 by solid-state reaction. X-ray diffraction at room and at elevated temperatures, Raman scattering and impedance spectroscopy were used to characterise the samples. The structure refinement of the composition x = 0.1 from neutron diffraction data reveals that tin is preferentially located in the tetrahedral layers of the brownmillerite. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007  相似文献   

10.
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   

11.
Several olivine phosphates were investigated in the last years as cathode materials for secondary lithium ion batteries. Among these compounds, LiFe x Co1 − x PO4 solid solutions might be interesting candidates because they should combine the high potential value of Co3+/Co2+ (higher than 4.5 V vs Li+/Li) with the relatively high charge–discharge rate of LiFePO4. Solid solutions were prepared by solid-state route and characterised by X-ray powder diffraction, cyclic voltammetry, impedance spectroscopy and the Hebb–Wagner method. The results show that also low amount of iron induces high electronic conductivity in the solid solutions.  相似文献   

12.
We have adopted a modified combustion route, namely, a mixed fuel process (MFP) to prepare a novel series of nano-crystalline single- and multiple-doped ceria compositions with controlled powder characteristics, large surface area, finer particle size, high sinterability, and high oxide ion conductivity at intermediate temperatures (500–700 °C). Using the mixed fuel process, we have prepared nano-particles of single- and multiple-doped ceria powders with dopants such as Ca, Gd, and Sm and a suitable combination of the same. In the pursuit for identifying new oxide-ion-conducting materials in this family of oxides, we have pursued the idea of co-doping effect on the single doped compositions with proper introduction of a second dopant. Effect of these dopants on the thermal decomposition and physico–chemical characteristics of the precursor and the powders prepared thereby were studied in detail. Finally, the effects of multiple co-doping on the microstructural and electrical properties were compared to understand the origin of the effect of dopant characteristics on the oxide ion conductivity of Ce1−x M x O2 solid solutions. Our experimental results established unequivocally that co-doping is very effective in identifying new materials with remarkably high ionic conductivity with substantial reduction in the cost for technological applications. Among the studied compositions, the maximum conductivity with minimum activation energy was observed for the triply co-doped CCGS composition (; E a = 0.56 eV), which is much higher compared to the conductivity exhibited by most of the reported co-doped ceria compositions. In conclusion, an effective way to improve the oxide ion conductivity of ceria-based oxides by proper choice of dopants and co-doping is achieved.  相似文献   

13.
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   

14.
The multi-walled carbon nanotubes (MWCNTs) wrapped with hexagonal wurtzite Zn x Cd1−x S nanoparticles with a uniform and small diameter have been prepared to form Zn x Cd1−x S–MWCNT heterostructures by microwave-assisted route using Zn(Ac)2, Cd(NO3)2, and thioacetamide as the reactants. The heterostructures have been characterized by X-ray powder diffraction, scanning and transmission electron microscopy, high-resolution transmission electron microscopy, photoluminescence (PL) and PL excited lifetime. Despite the analogous size and configuration, the Zn x Cd1−x S–MWCNT (x = 0, 0.2, 0.5, 0.8, 1) with different Zn concentration exhibit composition-dependent absorption properties in the visible zone. The PL peak positions of Zn x Cd1−x S–MWCNT change gradually from ZnS–MWCNT to CdS–MWCNT. The Zn x Cd1−x S–MWCNT shows different photocatalytic activity towards the photodegradation of fuchsin acid under visible light illumination, photocatalytic activity of the Zn x Cd1−x S–MWCNT decreases gradually with the increase in the Zn concentration, the Zn0.2Cd0.8S–MWCNT possessed the best photocatalytic activity. After recycling thrice, the photocatalysts still have about 85% efficiency.  相似文献   

15.
Ceramics powder of BaCe0.95Yb0.05O2.975 was successfully prepared by sol–gel method. Thermogravimetric analysis showed that the decomposition of the dried powder was completed at 1,000 °C. Three strongly exothermic peaks observed in differential thermogravimetric signal indicated three major stages of weight loss in the sample. The high crystallinity of sample with orthorhombic structure was confirmed by X-ray diffraction. The loose particles size obtained from scanning electron microscope was in the range of 65–100 nm, which is almost in the same range as that observed in particle size distribution. The sample showed a dc conductivity of ~1.3 × 10−4 S cm−1 at 650 °C and the activation energy, E a, was found to be 1.4 eV. Result of chemical stability test showed that the compound was unstable in atmosphere containing pure carbon dioxide.  相似文献   

16.
Microporous (TiO2) x –(SiO2)100 − x (0 < x < 40) xerogels have been produced by sol–gel methods either by partial pre-hydrolysis or reflux of tetraethoxysilane and titanium isopropoxide. These have been characterised by 29Si nuclear magnetic resonance, X-ray diffraction, EXAFS at the Ti–K edge, X-ray photoelectron spectroscopy, temperature-programmed reduction, FT infrared, N2 adsorption at 78 K (BET), transmission electron microscopy and dynamic light scattering (DLS). These were dip coated onto fused silica and characterised by atomic force microscopy and UV–visible absorption. Their photoactivity in removal of alkylphenol ethoxylate TX100 from water was less than for less porous titania. The advantages of including thermally removable PEG or PPG templates in terms of increasing surface, meso-porosity and photon absorbance at visible wavelengths to give nanoengineered photocatalytic films are described.  相似文献   

17.
Ronghua Li  Feiyan Gong  Wenji Wang 《Ionics》2006,12(6):353-363
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   

18.
M. Ganesan 《Ionics》2007,13(5):379-385
Lithium lanthanoid silicates are projected as promising solid electrolytes for solid-state high-temperature lithium batteries. Synthesis of Li1−x Sm1+x SiO4 (x = 0.2 to 0.6) was carried using sol–gel method, and these compounds were characterized by thermogravimetry differential thermal analysis, X-ray diffraction, Fourier transform infrared, and SEM. Impedance measurements were carried out at different temperatures, and conductivity at different temperatures was calculated. The effect of an increase of samarium content on the conductivity of the solid electrolyte was studied in this paper. It was found that less samarium content exhibits good conductivity at higher temperatures.  相似文献   

19.
In the present work, (1−x)(0.935Bi0.5Na0.5TiO3–0.065BaTiO3)–xKNbO3 (BNT–BT–KN, BNT–BT–100xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient of ∼10−2 m4 C−2 is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(Mg1/3Nb2/3)O3. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150°C. The large electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO3 substitution, and the high electrostrictive coefficient of BNT–BT–KN ceramics makes them great candidates to be applied in the new solid-state actuators.  相似文献   

20.
Solvent-free films of poly (ethylene oxide)–silver triflate (PEO–AgCF3SO3)/MgO-based nanocomposite polymer electrolytes (PEO)50AgCF3SO3x wt.% MgO (x = 1, 3, 5, 7, and 10) obtained using solution casting technique were found to exhibit an appreciably good complexation of MgO nanofiller within the polymer electrolyte system and non-Debye type of relaxation as revealed by Fourier transform infrared and complex impedance analyses. Optimized filler (5 wt.% MgO) when incorporated into the polymer electrolyte resulted in a maximum electrical conductivity of 2 × 10−6 S cm−1 in conjunction with a silver ionic transference number (t Ag+) of 0.23 at room temperature (298 K). Detailed structural, thermal, and surface morphological investigation indicated a slight reduction in the degree of crystallinity owing to the addition of MgO nanofiller.  相似文献   

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