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1.
The conductivity of glasses in the P2O5−[(1−x) V2O5−x Na2O] system is studied as a function of temperature and composition. For all compositions, the conductivity variations as a
function of temperature follow an Arrhenius type relationship:
. The activation energies and pre-exponential factors corresponding to the V2O5 richest compositions are lower than that corresponding to the ionic ones. Isothermal variations of the conductivity as a
function of composition show a deep minimum for a molar ratio x near 0.65. On either side of this minimum, the conductivity
is mainly electronic (x<0.7) or ionic (x>0.8). The variations are interpreted assuming a prevailing diluting effect of the
non predominantly present oxide without any interactions between the electronic and ionic charge carriers.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
2.
Ce0.9Gd0.1O1.95 (GCO), is one of the potential candidate electrolytes for intermediate temperature Solid Oxide Fuel Cells (ITSOFC). GCO has
high oxide ion conductivity in the intermediate temperature range (500 – 700 °C) compared to other Ce1−yGdyO2-2/y compositions and the Gd3+ ion is the most appropriate dopant material compared to other rare earth materials such as Sm3+, Y3+, Zr3+, etc. Our results show that the fuel cell H2/Pt/Ce0.9Gd0.1O1.95/Pt/O2 operated in the temperature range 500 – 700°C gives the maximum power densities 0.0049 W/cm2 at 500 °C and 0.0126 W/cm2 at 650 °C for cell voltages 0.6275 V and 0.6278 V, respectively, where the electrolyte was kept in 5% H2 (+ Argon) for 12 hours before use in the fuel cell. Maximum power densities are 0.0038 W/cm2 at 500 °C and 0.0270 W/cm2 at 650 °C for cell voltages 0.5986 and 0.5913 V, respectively, where the electrolyte was kept in 2 % O2 (+ Argon) for 12 hours before use in the fuel cell.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
3.
Doubly substitution of vanadium by Cu and Co in the limit of 10% in Bi4V2O11, has led to the formation of the Bi4V1.8Cu0.2−xCoxO10.7 solid solution. X-ray diffraction shows that all the compositions present a tetragonal symmetry. The thermal analysis has
revealed that the polymorph γ' phase, which is formed by a partial ordering of oxygen ions in the γ high temperature form,
is stabilized at room temperature. The influence of sintering temperature on the microstructure of the samples was investigated
by the scanning electron microscopy (SEM). The ceramics sintered at 820 °C for more than 3 hours present micro-craks. The
evolution of the electrical conductivity with temperature and the degree of substitution has been investigated by impedance
spectroscopy. The sample with x=0.1 presents the highest value of the conductivity ≈4.6×10−2 S·cm−1 at 600 °C. 相似文献
4.
L. Pintilie I. Pintilie D. Petre T. Botila M. Alexe 《Applied Physics A: Materials Science & Processing》1999,69(1):105-109
Thermally stimulated current (TSC) measurements performed in the 100 K–400 K temperature range on Bi4Ti3O12 (BiT) thin films annealed at 550 °C and 700 °C had revealed two trapping levels having activation energies of 0.55 eV and
0.6 eV. The total trap concentration was estimated at 1015 cm−3 for the samples annealed at 550 °C and 3×1015 cm−3 for a 700 °C annealing and the trap capture cross-section was estimated about 10−18 cm2. From the temperature dependence of the dark current in the temperature range 20 °C–120 °C the conduction mechanism activation
energy was found to be about 0.956–0.978 eV. The electrical conductivity depends not only on the sample annealing temperature
but also whether the measurement is performed in vacuum or air. The results on the dark conductivity are discussed considering
the influence of oxygen atoms and oxygen vacancies.
Received: 28 January 1998 / Accepted: 8 January 1999 / Published online: 5 May 1999 相似文献
5.
Pellicular γ-zirconium phosphate (γ-ZP(p)), i.e. sheets made up entirely of oriented lamellae of Zr(PO4)(H2PO4)·2H2O (γ-ZP), have been obtained by filtering colloidal dispersions of exfoliated γ-ZP in water/acetone. The ac-conductivity of
γ-ZP(p) and γ-ZP was measured in the temperature range 20/–20°C on samples previously conditioned at relative humidities between
90 and 5%. In both cases, the conductivity dependence on material hydration indicates the presence of a non-negligible bulk
transport at low relative humidities. For each relative humidity the conductivity data have been parameterised on the basis
of the Arrhenius equation. Activation energy and pre-exponential factor values suggest the presence of the same conduction
mechanism in both materials. The conductivity of γ-ZP(p) measured by applying the electric field parallel to the sheets ranges from 3·10−4 to 1·10−5 S cm−1 for relative humidity decreasing from 90 to 11%, being an order of magnitude higher than that of γ-ZP. Since the pellicular
and microcrystalline material have very similar surface areas (11–12 m2/g), the higher conductivity of γ-ZP(p) is mainly due to the preferred particle orientation parallel to the electric field.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
6.
Co-sintering of Cu-CGO cermet anodes on CGO (Ce0.8Gd0.2O2−δ) electrolyte was conducted at low temperature (1000 °C) by introducing small amounts (2 mol.%) of CuO sintering aid to the
electrolytic CGO. The Cu-CGO anodes with Cu contents from 20–50 vol.% were prepared by combustion synthesis followed by sintering
and reduction. Symmetrical anode/electrolyte/anode assemblies of Cu-GCO/CGO/Cu-CGO were fabricated by manually depositing
the anode combustion powder on a green substrate of the 2 mol% CuO-containing CGO, followed by co-pressing and co-sintering
of the assembly at 1000 °C. The low-temperature sintered CGO is submicron with 95–99% relative density. CuO addition has no
significant effect on either the total or ionic conductivity of the electrolyte, but p-type conduction in the temperature
range, 900–1200 °C, is 25 times higher than that of undoped CGO. Oxygen-ion transference numbers of the Cu-containing CGO
lie in the range 0.89–0.99, as determined by the modified e.m.f. technique under an oxygen/air potential gradient. The activation
energy for ionic conduction, 83 kJmol−1, is significantly lower than that for p-type electronic transport, 140 kJmol−1.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
7.
Potentiometric CO2 gas sensors with Li conducting glasses/glass ceramics of the system Li2O-Al2O3-SiO2 (different nominal composition) as solid electrolytes have been investigated. Li2CO3 was used as CO2 and O2 sensitive auxiliary electrode. During the sensor test measurements, the CO2 partial pressure was varied between 1×10−3 and 1×10−1 bar at a constant O2 partial pressure of 2.1×10−1 bar whereas N2 was used as carrier gas. Comparative measurements were accomplished with sensors comprising Na and K ion conducting glasses.
A metastable reference electrode was formed at the contact zone between the Au metal electrode and the former Li glasses of
definite nominal composition by crystallization processes taking place, which lead to stable, reproducible CO2 dependent EMF signals for more than 90d. The thermodynamically expected EMF difference and the observed EMF difference agree
quite well between 500 and 600 °C.
At 600 °C, the drift of sensors with glasses as solid electrolytes and direct Au glass/glass ceramics contact as reference
electrode amounts typically 0.32 mV/d (p(CO2)=1×10−3 bar, p(O2)=2.1×10−1 bar at the measuring electrode), if a metastable multiphase equilibrium is formed. At identical partial pressures of CO2 and O2, the signal reproducibility of these sensors with different solid electrolyte glasses of the same nominal composition lies
within 30 mV at 600 °C.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
8.
Serge Zhuiykov 《Ionics》2009,15(4):507-512
In situ Fourier transform spectroscopy (FTIR) was used to study interactions of nanostructured ruthenium oxide (RuO2) thin-film sensing electrode with O2 at room temperature. RuO2 nanostructures were pretreated at 1,000 °C for 1 h in order to obtain good crystallinity of amorphous RuO2 nanoparticles. Morphology and properties of nanostructured RuO2 were characterized by X-ray diffraction, thermo-gravimetric/differential thermal analysis, scanning electron microscopy,
and FTIR. It was shown that pretreated RuO2 is quite active for O2
−, O2
2−, and O2− adsorption with clear 722 cm−1 band for superoxide ions (O2
−) adsorption for the different oxygen concentrations. The results of in situ FTIR measurements revealed that the active sites
for oxygen adsorption are not limited to the triple boundaries, but extended to surfaces of RuO2 electrodes. Fundamental vibration frequencies of ruthenium–oxygen bond at a temperature of 23 °C as well as region above
fundamental frequencies for the nanostructured RuO2 were identified. 相似文献
9.
New sulfide glasses in the Li2S–Sb2S3–P2S5 system have been prepared by classical quenching technique where glassy domain remains up to 50% molar addition of Li2S and electrical conductivities have been determined by impedance spectroscopy. Room temperature DC conductivity vs Li2S content exhibits two regions implying different conductivity mechanisms. The compositions of low lithium content presented low electronic conductivities close to 0.01 μS/cm at room temperature (due to Sb2S3 semiconducting properties). The compositions of medium lithium content could result to mixed ionic–electronic conductors with predominant ionic conductivity with a maximum close to 1 μS/cm; Arrhenius behavior is found between 25 °C and T
g for all glasses, but activation energy is found to be somehow above most similar systems. A comparative study with glasses belonging to the other chalcogenide systems has been undertaken and values of the decoupling index are reported, and in order to validate conductivity data, a circuit equivalent circuit was proposed and fitted parameters were calculated with good agreement. 相似文献
10.
Perovskite-type lithium fast ion conductors of Li3xLa0.67−xScyTi1−2yNbyO3 system were prepared by solid state reaction. X-Ray powder diffraction shows that perovskite solid solution form in the ranges
of x=0.10, y≤0.10. AC impedance measurements indicate that the bulk conductivities and the total conductivities are of the
order of 10−4 S·cm−1 and 10−5 S·cm−1 at 25 °C respectively. The compositions have low bulk activation energies of about 17 kJ/mol in the temperature ranges of
298 – 523 K and total activation energies of about 37 kJ/mol in the temperature ranges of 298 – 523 K. 相似文献
11.
Serge Zhuiykov 《Ionics》2009,15(6):693-701
An alumina sensor using sub-micron RuO2 sensing electrode (SE) was fabricated and examined for potentiometric dissolved oxygen (DO) detection in water at a temperature
range of 9–35 °C. The electromotive force (emf) response at these temperatures was linear to the logarithm of DO concentration in the range from 0.6 to 8.0 ppm (log[O2], −4.71 to −3.59). RuO2-SE displays a Nernstian slope of −41 mV per decade at pH 8.0. It was also found that the response/recovery time to DO changes
were sluggish as the water temperature cools down. Response time T
90 to DO changes increased from 8 min at a temperature of 23 °C to about 30 min at a temperature of 9 °C. The proton conductivity
of hydrous RuO2 appears to be due to the dissociative adsorption of water and the formation of acidic OH groups in Ru (III,IV) cluster ions.
In strong alkaline solutions, the sensor’s emf exhibited a mixed potential of fast and slow electrochemical reactions involving DO, RuO4
2− and OH− ions. The results also revealed that as pH of the solution increases to pH 10.0–13.0, the response/recovery rate becomes
faster, stabilizing more or less quickly depending upon the solution alkalinity. Scanning electron microscopy, energy dispersive
X-ray-analysis and impedance spectroscopy techniques were used to examine respectively the morphology, crystalline structure
and electrochemical behaviour of sub-micron RuO2 oxides. 相似文献
12.
The structure, thermal expansion coefficients, electrical and electrochemical properties of Ce1−xMxO2−δ (M=Bi, La, Pr, Eu, Tb; x=0–0.30) solid solutions, prepared hydrothermally for the first time, are surveyed. For all cation
substitution a solubility limit depending on the cation size was found.
The uniformly small particle size (10–50 nm) of the hydrothermally prepared materials allows sintering of the samples into
highly dense ceramic pellets at 1300–1400 °C, a significantly lower temperature, compared to that at 1600–1650 °C required
for samples prepared by solid state techniques. X-ray absorption near edge spectroscopy (XANES) was used for the identification
of Tb3+/Tb4+ or Pr3+/Pr4+ ions. The maximum of total conductivity in all solid solutions was found for x ∼ 0.15–0.25 with electronic contribution to
the total conductivity ∼ 50 % for Tb/Pr substitution and close to zero in all other cases. The conductivity becomes more ionic
with decreasing Tb/Pr substitution. The thermal expansion coefficients, determined from high-temperature X-ray diffraction
data, are 11.7×10−6 K−1 for CeO2 and slowly decrease for Tb and increase for all other cases with increasing substitution.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
13.
C.S. Rout K. Ganesh A. Govindaraj C.N.R. Rao 《Applied Physics A: Materials Science & Processing》2006,85(3):241-246
Sensing characteristics of ZnO, In2O3 and WO3 nanowires have been investigated for the three nitrogen oxides, NO2, NO and N2O. In2O3 nanowires of ∼20 nm diameter prepared by using porous alumina membranes are found to have a sensitivity (defined as the ratio of the sensor resistance in the gas concerned to that in air) of about 60 for 10 ppm of all the three gases at a relatively low temperature of 150 °C. The response and recovery times are around 20 s. The sensitivity of these In2O3 nanowires is around 40 for 0.1 ppm of NO2 and N2O at 150 °C. WO3 nanowires of 5–15 nm diameter, prepared by the solvothermal process show a sensitivity of 20–25 for 10 ppm of the three nitrogen oxides at 250 °C. The response and recovery times are 10 s and 60 s, respectively. The sensitivity is around 10 for 0.1 ppm of NO2 at 250 °C. The sensitivity of In2O3 and WO3 nanowires is not affected by humidity even up to 90% relative humidity. The study also reveals that the sensing mechanism for the three nitrogen oxides have a commonality in that the desorption of oxygen is a crucial step in all the cases. PACS 07.07.Df; 85.35.-p; 82.35.Np 相似文献
14.
The electrical conductivity of perovskite-related oxides CaTi1−xAlxO3−δ and SrTi1−xAlxO3−δ (x=0−0.4) were investigated within the temperature range 900 to 1000 °C and the oxygen partial pressure range between 10−20 and 0.21 atm using a dc four-point technique. The materials investigated show predominantly p-type electronic conductivity
at high, n-type electronic conductivity at low, and ionic conductivity at intermediate oxygen partial pressures. The values
of ionic conductivity in CaTi1−xAlxO3−δ were found to be lower than those in CaTi1−xFexO3−δ. The effect of aluminium concentration on the high-temperature transport properties was examined.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
15.
The defect fluorite region of the ternary system ZrO2-Y2O3-TiO2 encompasses compositions which offer both, good electronic and oxygen ion conductivity which enable good catalytic activity
for the direct oxidation of methane in a solid oxide fuel cell (SOFC). The electrical properties of compositions YxTiyZr1−(x+y)O2−x/2 (with x=0.15, 0.2, 0.25 and y=0.15, 0.18) were characterised in order to find the composition with highest ionic and electronic
conductivity. High titanium dopant concentrations (Y) of 15 and 18 atom%, near the solubility limit of Ti4+ in the fluorite structure, have been introduced to achieve a high electronic conductivity at low oxygen partial pressure.
The yttrium content x has been varied between 15 and 25 atom% to find the fluorite composition with the highest ionic conductivity
for each titanium level.
In the pO2-range from 0.21 to 10−13 atm the conductivity is predominantly ionic and constant over that range. The maximum ionic conductivity is 0.01 Scm−1 for the compositions, which contain 15 atom% yttrium. Substantial electronic conductivity is introduced into the system at
low oxygen pressures below 10−13 atm via reduction of Ti4+ ions to Ti3+. The maximum electronic conductivity of 0.2 Scm−1 at 930 °C has been measured for a sample with 18 atom% titanium. The slope of all log(σ) vs. log(pO2) plots follows a pO
2
−1/4
-dependence.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
16.
Admittance spectra of the ion conducting glasses xNa2O(1−x)SiO2 and xK2O(1−x)SiO2,(x=0,1–0,3) have been studied on small signal conditions from room temperature to 713 K. Conductivity relaxation in the bulk
and space charge relaxation due to drift and diffusion near the electrodes were found in separated parts of the frequency
range 10−4–106 Hz. The data show Arrhenius behaviour for dc conductivity and conductivity relaxation. The determination of the charge carrier
concentration is based on the analysis of the beginning of space charge relaxation. The free carrier concentration, n0, were evaluated to be of the order of 1023 m−3 at temperatures 400 – 700 K and show a weak dependence on composition. The dominant factor determining conductivity was mobility
in these glasses. The strong temperature dependence of n0 below 400 K indicates changed conditions for the development of the space charge relaxation which are discussed.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept. 1994. 相似文献
17.
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
18.
Gold electrodes with known contact geometries were studied using impedance spectroscopy. From these data it was possible to
determine the specific polarisation conductivity per unit length of three-phase boundary (TPB). The values were found to be
(3÷22)×10−4 S·cm−1 dependent on the electrode history in pure oxygen at 977 °C and 2×10−6 S·cm−1 at 977 °C in “pure” hydrogen (PO2=10−20 atm at 1001 °C). The results are compared with previous data obtained for platinum electrodes. 相似文献
19.
Electrical conductivity and dielectric relaxation studies of silver ion-conducting glasses have been prepared using xAg2SO4-15Ag2O-(90-x)(90P2O5-10MoO3) glass system over a temperature range of 298–353 K and frequencies of 10 Hz to 10 MHz. DC conductivities exhibit Arrhenius behavior over the entire temperature range with a single activation barrier. The ac conductivity behavior of these glasses has been analyzed using single power law; conductivity increases linearly in logarithmic scale with Ag2SO4 concentration. The power law exponent (s) decreases, while stretched exponent (β) is insensitive to increase of temperature. Scaling behavior has also been carried out using the reduced plots of conductivity and frequency, which suggest that ion transport mechanism remains unaffected at all temperatures and compositions. 相似文献
20.
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 σ–T plots and DSC scans do complement each other in a particular range of composition. 相似文献