共查询到20条相似文献,搜索用时 46 毫秒
1.
The conductivity and transport number of oxygen ions of BiVO4-(5, 7, 10, 12) wt % V2O5 ceramic composites are measured using the four-probe and coulomb-volumetric methods, respectively, in the temperature range from 500 to 660°C. The phase transition of wetting of grain boundaries with eutectic melt at 640°C is discovered. It is shown that the grain boundary wetting significantly raises the ionic conductivity of composites. 相似文献
2.
Y. Akishige H. Shigematsu T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):537-540
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%. 相似文献
3.
La2Mo2O9 samples were prepared from freeze-dried powder precursors and characterized by XRD, TG/DTA, SEM, electrical and electrochemical measurements. Pellets with different density were obtained by sintering at temperatures between 900 and 1100 °C to obtain nearly dense samples with grain sizes in the range 1–8 m. The electrical conductivity was measured using impedance spectroscopy. The capacitance and relaxation frequencies of the main contributions to the spectra were used to ascribe the contributions of grain interiors and internal interfaces, and their temperature dependence. A coulometric titration technique was used to evaluate the change of oxygen stoichiometry under moderately reducing conditions, and to estimate the stability limits under strongly reducing conditions. An ion-blocking method was used to evaluate the onset of n-type conductivity, and a combination of these results with total conductivity measurements was used to obtain the ionic transport number. A combination of oxygen stoichiometry changes and ion-blocking results was used to obtain estimates of mobility.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003 相似文献
4.
L. A. Klinkova V. I. Nikolaichik N. V. Barkovskii V. K. Fedotov 《Russian Journal of Inorganic Chemistry》2007,52(9):1333-1339
New barium bismuth oxides have been synthesized under an argon atmosphere at 530 and 430°C, respectively: a Ba: Bi = 1 : 4 phase has a tetragonal perovskite structure, and a 1 : 15 phase has a rhombohedral structure. For the 1 : 4 phase, the unit cell parameters are a = 4.297(2) Å and c = 4.472(2) Å as determined by powder X-ray diffraction (XRD). Electron diffraction (ED) patterns show superstructure reflections with the vectors q 1= 1/17[530], q 2 = 1/17[3\(\bar 5\)0], and q 3 = 1/5[002]. These reflections point to an ordered arrangement of barium and bismuth ions in the supercell with the parameters √17a and 5c. The supercell of the 1 : 4 phase includes a ten-layer stack of metal-oxygen planes along the c axis. The rhombohedral 1 : 15 phase has the following hexagonal unit cell parameters as determined by XRD: a= 6.018(2) Å, c = 4.070(2) Å. In view of the superstructure on the ED patterns, the supercell parameters of the rhombohedral phase are 4a and 2c. The supercell of the 1 : 15 phase contains a six-layer stack of planes along the c axis. 相似文献
5.
T. Zhang L. Kong Z. Zeng H. Huang P. Hing Z. Xia J. Kilner 《Journal of Solid State Electrochemistry》2003,7(6):348-354
A 20% GdO1.5 doped ceria solid solution with a small amount of MnO2 doping (≤5% molar ratio) was prepared via the mixed oxide method from high-purity commercial powders with grain size around
0.2–0.5 μm. X-ray diffraction analysis indicated that all the samples exhibited the fluorite structure, and no new phase was
found. The data from dilatometeric measurements and scanning electron microscopy observations revealed that 1% Mn doping reduced
the sintering temperature by over 150 °C, and enhanced the densification and grain growth. Mn doping has little effect on
grain interior conductivity, but a marked deterioration in grain boundary behavior is observed. This leads to a lower total
conductivity in comparison with the undoped Ce0.8Gd0.2O2–δ. Therefore, for solid oxide fuel cells (SOFCs) with Mn-containing compounds as electrodes, optimization of electrode fabrication
conditions is needed to prevent the formation of a lower conductivity layer at the electrode/electrolyte interface since Mn
will diffuse from the electrode side to the electrolyte during fabrication and operation of SOFCs.
Electronic Publication 相似文献
6.
T. Bashir A. Shakoor E. Ahmed N. A. Niaz Shahid Iqbal Muhammad Saeed Akhtar Mohammad Azad Malik 《Polymer Science Series A》2017,59(6):902-908
This research paper comprises of the synthesis of polypyrrole (PPy)-Fe2O3 nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H c ), saturation magnetization (M s ) and remanence (M r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites. 相似文献
7.
A. Migdał-Mikuli N. Górska E. Szostak 《Journal of Thermal Analysis and Calorimetry》2007,90(1):223-228
Phase transition and thermal decomposition of hexadimethylsulfoxidealuminium chloride were studied by differential scanning
calorimetry (DSC), thermogravimetry (TG) and simultaneous differential thermal analysis (SDTA). The gaseous products of the
decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In the temperature range of 95–300 K, [Al(DMSO)6]Cl3 indicates one phase transition at T
ch=244.96 K (on heating) and at T
cc=220.87 K (on cooling). Large thermal hysteresis of the phase transition (∼24 K) indicates its first order character. Large
value of transition entropy (ΔS≈40 J mol−1 K−1) suggests its configurational character. Thermal decomposition of the title compound proceeds in four main stages. In the
first stage, which starts just above ca. 300 K, the compound loses two DMSO molecules per one formula unit and undergoes into
[Al(DMSO)4]Cl3. In the second stage, the next three DMSO ligands are released and simultaneously decomposed. The third stage, which continues
up to ca. 552 K, is connected with a loss of the last DMSO ligand and the formation of AlCl3. In the fourth stage AlCl3 reacts with carbon monoxide that originates from the decomposition of DMSO, and first aluminium oxychloride and next solid
Al2O3 plus carbon are created. 相似文献
8.
Alireza Jahangiri Majid Saidi Farhad Salimi Abolfazl Mohammadi 《Research on Chemical Intermediates》2018,44(3):1755-1773
In this study, nano catalyst LaNiO3 with perovskite structure was synthesized using the citrate sol–gel method in the combined methane reforming with CO2 and O2 (CRM). The effects of increasing the surface area of the LaNiO3 perovskite on the catalytic activity were investigated by changing the method of preparing and creating holes in the surface of the samples. Physical and chemical properties of the samples, before and after the reactor test, were determined through ICP, AA, XRD, TGA, TPR, BET, SEM, EDX and TEM techniques. The results of XRD, ICP, AA, SEM, EDX and TEM tests indicated that the citrate sol–gel method is a good way to prepare a homogeneous perovskite LaNiO3 sample on a scale of nanometers. The results of the TPR test showed using etching in the citrate sol–gel method can produce samples with high stability. The BET results indicated that the surface area of the LaNiO3 sample tripled with the method suggested in this paper. Changes in preparation method lead to induction time decreasing and temperature increasing. Use of etching in the citrate sol gel method had no significant effect in the results of activity tests versus time reaction at a temperature of 800 °C. TGA curves revealed no production of coke over the process for the produced samples. 相似文献
9.
Electrical conductivity in the monoclinic Li2TiO3, cubic Li1.33Ti1.67O4, and in their mixture has been studied by impedance spectroscopy in the temperature range 20–730 °C. Li2TiO3 shows low lithium ion conductivity, σ300≈10–6 S/cm at 300 °C, whereas Li1.33Ti1.67O4 has 3×10–8 at 20 °C and 3×10–4 S/cm at 300 °C. Structural properties are used to discuss the observed conductivity features. The conductivity dependences
on temperature in the coordinates of 1000/T versus loge(σT) are not linear, as the conductivity mechanism changes. Extrinsic and intrinsic conductivity regions are observed. The change
in the conductivity mechanism in Li2TiO3 at around 500–600 °C is observed and considered as an effect of the first-order phase transition, not reported before. Formation
of solid solutions of Li2–
x
Ti1+
x
O3 above 900 °C significantly increases the conductivity. Irradiation by high-energy (5 MeV) electrons causes defects and the
conductivity in Li2TiO3 increases exponentially. A dose of 144 MGy yields an increase in conductivity of about 100 times at room temperature.
Electronic Publication 相似文献
10.
The phase transition at T
p (~109 °C) of RbH2PO4 and its composite with SiO2 has been investigated by thermal analysis here. In the case of neat RbH2PO4, there is a linear relationship between endothermic peak temperature (T
m) and square root of heating rate (Φ
1/2), from which the onset temperature of phase transition can be determined. Besides, Kissinger method and another calculation
method were employed to obtain the activation energy of phase transition. The detailed deduction process was presented in
this paper, and the estimated activation energies are E
1 ≈ 126.3 kJ/mol and E
2 ≈ 129.2 kJ/mol, respectively. On the other hand, the heterogeneous doping of RbH2PO4 with SiO2 as dopant facilitates its proton conduction and leads to the disappearance of jump in conductivity at T
p. The heats of transition in the composites decrease gradually with increasing the molar fraction of SiO2 additives. In the cooling process, a new and broad exothermic peak appeared between ~95 and ~110 °C, and its intensity also
changes with the SiO2 amount. These phenomena might be related to the formation of amorphous phase of RbH2PO4 on the surface of SiO2 particles due to the strong interface interaction. 相似文献
11.
T. A. Zhuravleva 《Russian Journal of Electrochemistry》2011,47(6):676-680
The influence of doping with copper oxide on the phase composition, electric conductivity, and linear thermal expansion coefficient
(LTEC) of SmBaCo2O5 + δ and NdBaCo2O5 + δ was studied. The sample homogeneity region has been determined with using XRD. The samples conductivity decreased as the
dopant concentration increased. The character of the temperature dependence of conductivity changed at high copper contents.
In a reductive atmosphere, the conductivity of the samples at first decreased and then remained constant. The linear thermal
expansion coefficient decreased as the amount of the incorporated dopant increased. 相似文献
12.
Yttrium
orthoborate crystallizes in the vaterite-type structure and has two polymorphous
forms, viz. a low- und a high temperature one. DTA measurements of YBO3
confirmed a reversible phase transition with a large thermal hysteresis. The
phase transition has been accurately characterized by the application of different
heating and cooling rates (β). Consequently, the extrapolation of the
experimental data to zero β yields the transition points at 986.9°C
for the heating up and at 596.5°C for the cooling down cycle. These values
correspond to samples just after treatment at 1350°C. For samples with
a different ‘thermal history’ other phase transition temperatures
are observed, (e.g. after having performed several heating and cooling cycles).
The linear relationship between the associated DTA signal ΔT=T
onset–T
offset and the square root
of the heating rate β was confirmed, but the relation between T
onset and square root of β
is not found here.
From the empirical data a good linear fitting
between T
onset and
ln(β+1) can be derived.
From the kinetic analysis (Kissinger
method) of the phase transformation of YBO3 an apparent
activation energy of about 1386 kJ mol–1
for heating and of about 568 kJ mol–1 for
cooling can be determined 相似文献
13.
The present research work reports the study on crystal structure, vibrational spectroscopy and thermal analysis of organic-inorganic hybrid compound (C6H5(CH2)2NH3)2CdCl4. Single crystals of bis(phenethylammonium)tetrachlorocadmate (C6H5(CH2)2NH3)2CdCl4 (PEA–Cd) were obtained by diffusion at room temperature. This compound crystallizes in the orthorhombic space group C2cb with unit cell parameters a = 7.4444(2) Å, b = 38.8965(3) Å, c = 7.3737(2) Å and Z = 4. Single crystal structure has been solved and refined to R = 0.036 and wR = 0.092. The structure consists of an extended [CdCl4]2– network and two [C6H5(CH2)2NH3]+ cations to form a two-dimensional perovskite system. The infrared (IR) spectrum of the title compound was recorded at room temperature. Differential scanning calorimetry (DSC) was used to investigate the phase transition; this compound exhibits a reversible single solid-solid phase transition. 相似文献
14.
Nemat Tahmasbi Somayeh Madmoli Parisa Farahnak Shahram Barzegar Hamze Moayeri 《Russian Journal of Applied Chemistry》2017,90(9):1488-1493
In the paper cesium tungstate nanofibers for the first time have been fabricated successfully by a simple electrospinning technique followed by heat treatment. The cesium tungstate nanofibers have been characterized by XRD, SEM, and FTIR techniques. The results indicated the morphology and quality of the annealed electrospun samples are strongly dependent on the citric acid content within electrospinning solution. It is found with increasing the citric acid content from 7 to 22% the samples morphology changed from a particle structure to a fibrous structure. The average diameter of nanofibers was ~350 nm. XRD analysis reveals that all of the samples have good crystallinity with the same diffraction peaks that can be indexed to the tetragonal phase of Cs2W3O10. Furthermore, the photocatalyst properties of cesium tungstate has not been reported to date. In the work the synthesized Cs2W3O10 nanofibers were found to exhibit photocatalytic performance in the photodegradation of RhB aqueous solution used as a pollutant model. 相似文献
15.
Specific conductivity of molten salt mixtures of the LiF-ZrF4, NaF-ZrF4, KF-ZrF4, RbF-ZrF4, and CsF-ZrF4 systems is measured in the whole concentration range using the reference capillary technique. The results are presented in the form of equations of the χ = a + bT + cT 2 [S m?1] type. The concentration dependences of molar conductivity are calculated on the basis of the density data. The obtained regularities are explained in the terms of the complex model of ion melt structures. 相似文献
16.
N. I. Kadyrova Yu. G. Zainulin V. L. Volkov G. S. Zakharova A. V. Korolev 《Russian Journal of Inorganic Chemistry》2007,52(6):825-828
Perovskite-like nonstoichiometric oxide La x Cu3V4O12 (space group Im \(\bar 3\), Z = 2, a = 7.313–7.354 Å) with cation-site vacancies has been prepared for the first time at high pressures (p = 6.0–8.0 GPa) and high temperatures (T = 700–1100°C). The compound has metal-type conductivity and paramagnetic properties, and undergoes a phase transition. 相似文献
17.
T. I. Krasnenko M. V. Rotermel R. F. Samigullina 《Russian Journal of Inorganic Chemistry》2017,62(4):413-417
The previously unknown effect of emergence of an associated non-autonomous phase upon heating of zinc pyrovanadate Zn2V2O7 within the region of negative volume expansion is detected. Comparison of the data of high-temperature X-ray diffraction of the Zn2V2O7 samples synthesized via solution and solid-phase routes shows that the grain size affects the stabilization of the non-autonomous phase. The presence of a non-autonomous phase results in self-dispersion of the substance upon phase transition in heating–cooling cycles. 相似文献
18.
A. A. Il’ina I. A. Stenina E. P. Kharitonova A. B. Yaroslavtsev 《Russian Journal of Inorganic Chemistry》2007,52(11):1643-1647
Phase transitions and cation mobility in double molybdates K2M 2 II (MoO4)3 with M = Mg or Co and the products of their heterovalent doping with scandium(III) and vanadium(V) have been studied. The transition from low to high conductivity in K2M 2 II (MoO4)3 is the result of a two-stage phase transition, whose occurrence is significantly extended in time. Heterovalent substitutions noticeably decrease the heat of the phase transition. The transition to the low-temperature phase is not achieved even after long-term exposure. 相似文献
19.
Edward Mikuli Marta Liszka-Skoczylas Joanna Hetmańczyk Janusz Szklarzewicz 《Journal of Thermal Analysis and Calorimetry》2010,102(3):889-897
[Mn(NH3)6](NO3)2 crystallizes in the cubic, fluorite (C1) type crystal lattice structure (Fm \( \overline{3} \) m) with a = 11.0056 Å and Z = 4. Two phase transitions of the first-order type were detected. The first registered on DSC curves as a large anomaly at T C1 h = 207.8 K and T C1 c = 207.2 K, and the second registered as a smaller anomaly at T C2 h = 184.4 K and T C2 c = 160.8 K (where the upper indexes h and c denote heating and cooling of the sample, respectively). The temperature dependence of the full width at half maximum of the band associated with the δs(HNH)F1u mode suggests that the NH3 ligands in the high temperature and intermediate phase reorientate quickly with correlation times in the order of several picoseconds and with activation energy of 9.9 kJ mol?1. In the phase transition at T C2 c probably only a some of the NH3 ligands stop their reorientation, while the remainders continue to reorientate quickly with activation energy of 7.7 kJ mol?1. Thermal decomposition of the investigated compound starts at 305 K and continues up to 525 K in four main stages (I–IV). In stage I, 2/6 of all NH3 ligands were seceded. Stages II and III are connected with an abruption of the next 2/6 and 1/6 of total NH3, respectively, and [Mn(NH3)](NO3)2 is formed. The last molecule of NH3 per formula unit is freed at stage IV together with the simultaneous thermal decomposition of the resulting Mn(NO3)2 leading to the formation of gaseous products (O2, H2O, N2 and nitrogen oxides) and solid MnO2. 相似文献
20.
I. E. Animitsa E. N. Dogodaeva S. S. Nokhrin O. A. Kosareva A. Ya. Neiman 《Russian Journal of Electrochemistry》2010,46(7):734-740
Perovskite phases Ba3In2ZrO8 and Ba4In2Zr2O11 with the nominal concentration of structural oxygen vacancies 1/9 and 1/12, respectively, were synthesized by solid-phase
and solution methods. X-ray diffraction showed cubic symmetry of both phases with the unit cell parameter a = 0.4193(2) and 0.4204(3) nm, respectively. The absence of superstructural lines resulted in the conclusion on statistical
arrangement of oxygen vacancies. Thermogravimetry and mass spectrometry proved that both phases can reversibly absorb water
from gas phase (pH2O = 2 × 10−2 atm) with observed correlation between the concentration of oxygen vacancies and amount of absorbed water. The total water
amount was up to 0.9 mol per formula unit or, if recalculated for perovskite unit ABO3, 0.3 and 0.23 mol H2O, respectively. The temperature curves of coductivity in the atmosphere with various partial water vapor pressures (pH2O = 3 × 10−5 and 2 × 10−2 atm) showed significantly higher conductivity and lower activation energy (0.52 eV) in humid atmosphere due to proton transfer.
The proton conductivity is up to 5 × 10−4 Ohm−1 cm−1 at 300°C for Ba3In2ZrO8 specimen. IR spectrometry showed that protons in the structure exist primarily in OH-groups. 相似文献