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1.
BICO0.20?xNIxVOX solid electrolyte in the composition range 0 ≤ x ≤ 0.20 was synthesized by standard solid-state reactions. The influence of Ni substitution for Co on the relationship between the phase stabilization and electrical performance was investigated by means of X-ray powder diffraction (XRPD), differential thermal analysis (DTA) and AC impedance spectroscopy. The highly conductive γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.13 whose thermal stability increases with Ni content. On the other hand, complex plane plots of impedance suggested a major contribution of polycrystalline grain interiors to the overall electrical conductivity and the fastest oxygen-vacancy diffusion in the perovskite vanadate layers at x = 0.13. The dielectric permittivity measurements revealed the fact that suppression of the ferroelectric transition is compositionally dependent. However, a maximum ionic conductivity at lower temperatures (~2.56 × 10?4 S cm?1 at 300 °C) was observed for the composition with x = 0.13. 相似文献
2.
Samples of Co–Ni double substituted bismuth vanadate, BICO0.20?x NI x VOX (Bi4Co0.20???x (III)Ni x (II)V1.8O10.8???(x/2)???δ ;0?≤?x?≤?0.20) were synthesized by standard solid state reactions. The influence of Ni substitution for Co on phase stabilization and oxide-ion performance have been investigated using X-ray powder diffraction, differential thermal analysis, and AC impedance spectroscopy. The high conducting γ′-phase was effectively stabilized at room temperature for compositions with x?≥?0.13 whose thermal stability increases with Ni content. The complex plane plots of impedance were typically represented at temperatures below 380 °C, suggesting a major contribution of polycrystalline grains to the overall electrical conductivity. The dielectric permittivity measurements revealed the fact that suppression of the ferroelectric transition is compositionally dependent. Interestingly, the maximum ionic conductivity at lower temperatures (~2.56?×?10?4 S cm?1 at 300 °C) was observed for the composition with x?=?0.13. However, a good agreement was generally found between the values of electrical conductivity and corresponding activation energies of conduction. 相似文献
3.
Samples of Sn4+-substituted bismuth vanadate, formulated as Bi4Sn x V2? x O11?( x /2)? δ in the composition range 0.07 ≤ x ≤ 0.30, were prepared by standard solid-state reactions. Sample characterization and the principal phase transitions (α ? β, β ? γ and γ′ ? γ) were investigated by FT-IR spectroscopy, X-ray powder diffraction, differential thermal analysis (DTA) and AC impedance spectroscopy. For composition x = 0.07, the α ? β and β ? γ phase transitions were observed at temperatures of 451 and 536°C, respectively. DTA thermograms and Arrhenius plots of conductivities revealed the γ′ ? γ phase transition at 411 and 423°C for x = 0.20 and 0.30, respectively. AC impedance plots showed that conductivity is mainly due to the grain contribution, which is evident in the enhanced short-range diffusion of oxide ion vacancy in the grains with increasing temperature. The highest ionic conductivity (5.03 × 10?5 S cm?1 at 300°C) was observed for the x = 0.17 solid solution with less pronounced thermal hysteresis. 相似文献
4.
Samples of bismuth lead vanadium oxide (BIPBVOX) (Bi2V1–xPbxO5.5–x/2) singly substituted system in the composition range 0.05 ≤ x ≤ 0.20 were prepared by sol–gel synthesis route. Structural investigations were carried out by using a combination of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique. Energy dispersive X-ray spectroscopy analysis (EDXA) of doped samples was carried out to predict the sample purity and doping concentration. Transitions, α?β, β?γ and γ′?γ were detected by XRD, DTA and variation in the Arrhenius plots of conductivity. The ionic conductivity was measured by AC impedance spectroscopy. The solid solutions with composition x ≤ 0.07 undergo α?β phase transition, at 329 °C and β?γ phase transition at 419 °C. The highly conducting γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.17 whose thermal stability increases with Pb content. At 300 °C, the highest value of conductivity 6.234 × 10?5 S cm?1 was obtained for composition x = 0.15 and at 600 °C the highest value of conductivity 0.65 S cm?1 is observed for x = 0.17. AC impedance plots reveal that the conductivity is mainly due to the grain contribution to oxide ion conductivity. 相似文献
5.
The conductivity and thermal stability of H+(H2O)n β″ and ion rich β alumina single crystals have been measured by the complex impedance method in the 25–700°C temperature range. Two mechanisms of conductivity were assumed: proton transfer at lower temperatures and H3O+ diffusion in the high-temperature range. Both structures have similar properties, but ion rich β alumina possesses the best stability and the lowest activation energy (β: 0.15 eV, β″: 0.20 eV below 400 and 300°C respectively). The room-temperature conductivity is ≈5×10?6 Ω?1 cm?1. The conducting properties and mechanisms are discussed and compared to other protonic or ionic conductors. 相似文献
6.
The KFeP2O7 compound was prepared by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction. The AC electrical conductivity and the dielectric relaxation properties of this compound have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies and temperatures, 200 Hz–5 MHz and 553–699 K, respectively. Both impedance and modulus analysis exhibit the grain and grain boundary contribution to the electrical response of the sample. The temperature dependence of the bulk and grain boundary conductivity were found to obey the Arrhenius law with activation energies Eg?=?0.94 (3)?eV and Egb?=?0.89 (1)?eV. The grain-and-grain boundary conductivities at 573 K are 1.07?×?10?4 and 1.16?×?10?5 (Ω?1 cm?1). The scaling behavior of the imaginary part of the complex impedance suggests that the relaxation describes the same mechanism at various temperatures. The near value of the activation energies obtained from the equivalent circuit, conductivity data, and analysis of M″ confirms that the transport is through ion hopping mechanism. 相似文献
7.
The phase transformation in calcite I-IV-V and calcite ? aragonite have been characterized by electrical impedance measurements at temperatures 600–1200°C and pressures 0.5–2.5?GPa in a piston cylinder apparatus. The bulk conductivity σ has been measured from Argand plots in the frequency range 105–10?2?Hz in an electric cell representing a coaxial cylindrical capacitor. The synthetic polycrystalline powder of CaCO3 and natural crystals of calcite were used as starting materials. The transformation temperature Tc was identified from resistivity-temperature curves as a kink point of the activation energy. At pressure above 2?GPa in ordered phase calcite I, the activation energy E σ is c. 1.05?eV, and in disordered phase calcite V E σ is c. 0.75?eV. The pressure dependence of Tc for the rotational order–disorder transformation in calcite is positive for pressures <1?GPa and negative for pressures >1?GPa. The transformation boundary of calcite 1–IV is observed only during first heating in samples after a long annealing at low temperatures. The activation energy of calcite I???IV decreases gradually from 1.8 to 1.05?eV with the pressure increase from 0.5 to 2?GPa. The kinetics of calcite ? aragonite transformation has been monitored by measuring a time-variation of the electrical resistance of a calcite sample at 103?Hz in the stability P-T field of aragonite. The variation of the impedance correlates with the degree of phase transformation, estimated from X-ray powder diffraction studies on quenched products of experiments. The kinetics of calcite ? aragonite transformation may be fitted to the Avrami kinetics with the exponent m???1–1.5. 相似文献
8.
Abstract The energy shift of the He 11S0?21P1 transition, ΔE(n), can be used to determine the density, n, of He in bubbles in metals. A self-consistent band structure calculation for solid fcc He yields a linear relationship ΔE=C.n with C th=22 × 10?3 eV nm3. Systematic electron energy loss spectroscopy and transmission electron microscopy studies of He bubbles in Al for various He doses and temperatures result in Cexp=(24±8).10?3 eV nm3 in agreement with theory. The analysis is consistent with the assumption that dislocation loop punching is the dominant bubble growth mechanism during high-dose room temperature implantation. The application to He bubbles in Ni indicates a maximum He density of n=0.2 × 103 nm?3 for which He should be solid at room temperature. 相似文献
9.
Shishir Kumar Singh Himani Gupta Liton Balo Shalu Varun Kumar Singh Alok Kumar Tripathi Yogendra Lal Verma Rajendra Kumar Singh 《Ionics》2018,24(7):1895-1906
High molecular weight polymer poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI), and salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based free-standing and conducting ionic liquid-based gel polymer electrolytes (ILGPE) have been prepared by solution cast method. Thermal, electrical, and electrochemical properties of 80 wt% IL containing gel polymer electrolyte (GPE) are investigated by thermogravimetric (TGA), impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). The 80 wt% IL containing GPE shows good thermal stability (~?200 °C), ionic conductivity (6.42?×?10?4 S cm?1), lithium ion conductivity (1.40?×?10?4 S cm?1 at 30 °C), and wide electrochemical stability window (~?4.10 V versus Li/Li+ at 30 °C). Furthermore, the surface of LiFePO4 cathode material was modified by graphene oxide, with smooth and uniform coating layer, as confirmed by scanning electron microscopy (SEM), and with element content, as confirmed by energy dispersive X-ray (EDX) spectrum. The graphene oxide-coated LiFePO4 cathode shows improved electrochemical performance with a good charge-discharge capacity and cyclic stability up to 50 cycles at 1C rate, as compared with the without coated LiFePO4. At 30 °C, the discharge capacity reaches a maximum value of 104.50 and 95.0 mAh g?1 for graphene oxide-coated LiFePO4 and without coated LiFePO4 at 1C rate respectively. These results indicated improved electrochemical performance of pristine LiFePO4 cathode after coating with graphene oxide. 相似文献
10.
The structure of Na6.69Ca3.355(SO4)6Cl0.77F0.63, isostructural with fluorapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed a space group P63/m with lattice parameters of a?=?9.477 (2) Å, c?=?6.865 (5) Å. Final refinement led to R F?=?1.83 % and R B?=?7.64 %. The location of Na+ ions in the M (2) sites surrounding the channels was related particularly to the high polarizability of the Ca2+. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at σ 500 °C?=?1.03?×?10?5?S?cm?1 and Ea?=?0.70 eV. 相似文献
11.
Vilve Nummert Mare Piirsalu Ilmar A. Koppel 《Journal of Physical Organic Chemistry》2013,26(4):352-359
The second‐order rate constants k (dm3mol?1s?1) for alkaline hydrolysis of meta‐, para‐ and ortho‐substituted phenyl esters of benzoic acid, C6H5CO2C6H4‐X, in aqueous 50.9% (v/v) acetonitrile have been measured spectrophotometrically at 25 °C. In substituted phenyl benzoates, C6H5CO2C6H4‐X, the substituent effects log kX ? log kH in aqueous 50.9% acetonitrile at 25 °C for para, meta and ortho derivatives showed good correlations with the Taft and Charton equations, respectively. Using the log k values for various media at 25 °C, the variation of the ortho substituent effect with solvent was found to be precisely described with the following equation: Δlog kortho = log kortho ? log kH = 1.57σI + 0.93σ°R + 1.08EsB ? 0.030ΔEσI ? 0.069ΔEσ°R, where ΔE is the solvent electrophilicity, ΔE = ES ? EH20, characterizing the hydrogen‐bond donating power of the solvent. We found that the experimental log k values for ortho‐, para‐ and meta‐substituted phenyl benzoates in aqueous 50.9% acetonitrile at 25 °C, determined in the present work, precisely coincided with the log k values predicted with the equation (log kX)calc = (log kHAN)exp + (Δlog kX)calc where the substituent effect (Δlog kX)calc was calculated from equation describing the variation of the substituent effect with the solvent electrophilicity parameter, using for aqueous 50.9% CH3CN the solvent electrophilicity parameter, ΔE = ?5.84. In going from water to aqueous 50.9% CH3CN, the ortho inductive term grows twice less as compared with the para polar effect. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
12.
Jinglei Li Xiaobo Zhao Tian Zhang Xiaoshi Qian Ying Hou Lu Yang 《Phase Transitions》2017,90(1):99-103
ABSTRACTRelaxor ferroelectric polymer poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) (P(VDF-TrFE-CFE)) and its blends have been shown to exhibit a giant electrocaloric effect (ECE) over a broad temperature range, e.g. from 0 to 50 °C. Here, a special calorimeter was designed to directly characterize the heat absorbed QECE due to ECE cooling of the blend of P(VDF-TrFE-CFE) with P(VDF-TrFE) 65/35 mol% copolymer down to ?15 °C, which covers the temperature range for many refrigeration applications. From QECE, the isothermal entropy change ΔS and adiabatic temperature change ΔT are deduced. The data reveal that at ?15 °C the relaxor terpolymer/copolymer blend generates ΔS = 23.0J kg?1 K?1 and ΔT = 5.1K under 100 MV/m, which are still more than 65% of the ECE at room temperature. This temperature is far below the dielectric peak temperature of the relaxor blend and the results reveal the promise of the relaxor polymers for a broad range of EC cooling applications. 相似文献
13.
We report blend-based plastic polymer electrolyte (i.e., polyethylene oxide (PEO)–polydimethyl siloxane (PDMS)–lithium hexafluorophosphate (LiPF6)) with substantial improvement in DC conductivity at ambient and subambient temperatures when compared with literature reports. Conductivity variation with salt concentration, investigated within ±30 °C range, indicates an optimum conductivity of 5.6?×?10?5 S cm?1 at 30 °C for Ö/Li ~10 with a further lowering by one order at 0 °C and it remains unaltered at ?10 °C. Enhanced conductivity in this blend electrolyte, though lower than two copolymer counterparts, is attributed to very low glass transition temperatures of the host polymers. X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggest an effective blending between the two polymers with an effective interaction between the Li salt and the blend polymer matrix. Raman spectroscopy results indicated that cation (Li+) coordination occurs at the C=Ö site in PEO out of the two electron-rich sites (i.e., CÖ and Si–Ö–Si) in the PEO–PDMS blend. The blend electrolytes are predominantly ionic (t ion ~97 %). 相似文献
14.
Samples of Bi4Ca x V2? x O11?(3 x /2)?δ in the composition range 0.07 ≤ x ≤ 0.30 were prepared by conventional solid state reactions. The stability of different phases as a function of composition was analysed by X-ray powder diffraction, FT-IR spectra, differential thermal analysis and AC impedance spectroscopy. For the compositions x ≤ 0.10, monoclinic α-phase structure is retained at room temperature. For x = 0.13, orthorhombic β-phase is observed, whereas for x ≥ 0.17, high O2?conducting tetragonal γ-phase is stabilised. However, the highest ionic conductivity σ300°C = 3.27 × 10?4 S cm?1 was observed for x = 0.17. This higher value of conductivity of the substituted compound as compared to the parent compound can be attributed to the increased oxygen ion vacancies generated as a result of cation doping. AC impedance spectroscopy reveals the fact that this ionic conductivity is mainly due to the grain contribution. 相似文献
15.
This article presents the results of in situ X-ray powder diffraction, Raman spectroscopy, and electrical impedance spectroscopy of the α-phase of Bi2O3, at 0.1 MPa in the temperature range below and above the α–δ-phase transition. This work demonstrated subtle nonlinear temperature variations of the cell parameters, of the hard-mode Raman shift, and of the activation energy of electrical conductivity in the temperature range about 100–120°C below the α–δ phase transition temperature T Tr ≈ 725°C in Bi2O3. At T < 600°C, the linear variation of the inverse dielectric susceptibility (χ ?1) correlates well with the hard mode frequency shift Δ(ω 2) of Raman A1g mode as Δ(χ ?1)/Δ(ω 2) ≈ 5.5 × 10?7 cm2. A structural model describing the mechanism of O2? anion distribution and electric dipole disordering in the vicinity of T Tr is discussed. 相似文献
16.
B. K. Kardashev T. S. Orlova B. I. Smirnov A. Gutierrez J. Ramirez-Rico 《Physics of the Solid State》2013,55(9):1884-1891
Microstructural characteristics and amplitude dependences of the Young modulus E and of internal friction (logarithmic decrement δ) of bio-carbon matrices prepared from beech tree wood at different carbonization temperatures T carb ranging from 600 to 1600°C have been studied. The dependences E(T carb) and δ(T carb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the decrement with increasing carbonization temperature, namely, ΔE ~ AΔT carb and Δδ ~ BΔT carb, with A ≈ 13.4 MPa/K and B ≈ ?2.2 × 10?6 K?1 for T carb < 1000°C and A ≈ 2.5 MPa/K and B ≈ ?3.0 × 10?7 K?1 for T carb > 1000°C. The transition observed in the behavior of E(T carb) and δ(T carb) at T carb = 900–1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For T carb < 1000°C, the elastic properties are governed primarily by the amorphous matrix, whereas for T carb > 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic characteristics at a temperature close to 1000°C correlates with the variation of the physical properties, such as electrical conductivity, thermal conductivity, and thermopower, reported in the literature. 相似文献
17.
Heat capacities of [Fe(phen)2(NCS)2] and [Fe(phen)2(NCSe)2] were measured between 135 and 375 K. A heat capacity anomaly due to the spin-transition from low-spin 1A1 to high-spin π2 electronic ground state was found at 176·29 K for the SCN-compound and at 231·26 K for the SeCN-compound, respectively. Enthalpy and entropy of transition were determined to be ΔH = 8·60 ± 0·14 kJ mol?1 and ΔS = 48·78 ± 0·71 J K?1 mol?1 for the SCN-compound and ΔH = 11·60 ± 0·44 kJ mol?1 and ΔS = 51·22 ± 2·33 J K?1 mol?1 for the SeCN-compound. To account for much larger value of ΔS compared with the magnetic contribution, we suggest that there is significant coupling between electronic state and phonon system. We also present a phenomenological theory based on heterophase fluctuation. Gross aspects of magnetic, spectroscopic, and thermal behaviors were satisfactorily accounted for by this model. To examine closely the transition process, infrared spectra were recorded as a function of temperature in the range 4000 ? 30 cm?1. The spectra revealed clearly the coexistence of the 1A1, and the 5T2 ground states around Tc. 相似文献
18.
New materials of the K3 ? 2x Pb x PO4 system with high potassium-cation conductivity have been synthesized and studied. It has been found that the introduction of Pb2+ cations substantially increases the conductivity of K3PO4 due to the formation of potassium vacancies and the stabilization of the high-temperature cubic structure of the orthophosphate. At low temperatures, the maximum conductivity has been observed in the composition range x = 0.15–0.20 and varies from ~10?2 S cm?1 at 400°C to ~10?1 S cm?1 at 700°C. The factors influencing the transport properties of the materials under study have been discussed. 相似文献
19.
Saba Beg 《Phase Transitions》2015,88(11):1074-1085
Bi4V2O11-δ has been doped with Ce and Cd to study double substitution. The system with various dopant concentrations (0.07 ≤ x ≤ 0.30) was prepared by the standard solid-state reaction method. The correlation between the polymorphism and oxide ion performance was well investigated as a function of temperature and composition with the help of thermal analysis, X-ray diffraction (XRD) and AC impedance spectroscopy. From XRD results it is seen that the high oxide ion conducting tetragonal γ-phase is stabilized for x = 0.17. For the compositions x ≤ 0.10, monoclinic α-phase is retained at room temperature with clear evidence for two successive phase transitions α ? β and β ? γ. For x = 0.13, β ? γ phase transition is seen. However, the existence of order–disorder, γ' ? γ transition was confirmed for x = 0.17. It is seen that the highest low-temperature ionic conductivity at 320 °C is 3.19 × 10?4 S cm?1 which was observed for x = 0.17. 相似文献
20.
In this study, the effects of addition of sodium citrate dosages and different pH levels on the electrochemical behavior of CoFeNiCu alloy baths (electrolytes containing metal ions) were investigated. Stability (Pourbiax) diagrams and also speciation diagrams of cobalt, iron, nickel and copper, in conventional and citrate-added CoFeNiCu bath, were calculated by ChemEQL V.3.0 software. Stability diagrams showed that addition of 20 g?L?1 sodium citrate to the bath increased the pH of formed detrimental metal hydroxides (especially Fe(OH)3 from pH 3.4 to pH?~?6.9) through forming stable complexed species that were more stable than metal hydroxides at low pH levels (< ~3). According to the speciation diagrams, both pH level and sodium citrate dosage had noticeable effect on the distribution of species in the baths. Generally, at low pH level and/or sodium citrate dosage, Co++, Fe++, Ni++, and Cu++ species were dominant. The concentration of complexed species of Co(C6H5O7)? ( at pH?>?~ 7.5 or sodium citrate dosage?>?~ 30 g?L?1), Fe(C6H5O7)? (at pH?>?~ 5.5 or sodium citrate dosage?>?~ 25 g?L?1), Ni(C6H5O7)? (at pH?>?~ 6 or sodium citrate dosage?>?~ 30 g?L?1), and Cu(OHC6H5O7)2? ( at pH?>?~ 8 or sodium citrate dosage?>?~ 20 g?L?1) became significant. The effects of sodium citrate and reverse potential (E λ) on cyclic voltammetry curves were also studied. The addition of sodium citrate in the bath shifted the reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt, iron, and nickel simultaneously with copper, it was necessary to increase E λ value gradually with sodium citrate dosage; otherwise, only copper would have deposited from citrate-added CoFeNiCu bath. The study of speciation diagrams showed that reduction of metals from CoFeNiCu bath with natural pH (no acid or base is added to adjust pH and it was?~?5.2) and containing 20 g?L?1 of sodium citrate mainly occurred directly from complexed species. 相似文献