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Showing papers on "Conductivity published in 2015"


Journal ArticleDOI
TL;DR: Four-probe measurements show that the room temperature conductivity of this material can reach up to 1,580 S cm−1, which is the highest value ever reported for coordination polymers, and it displays ambipolar charge transport behaviour and extremely high electron and hole mobilities under field-effect modulation.
Abstract: Currently, studies on organic two-dimensional (2D) materials with special optic-electronic properties are attracting great research interest. However, 2D organic systems possessing promising electrical transport properties are still rare. Here a highly crystalline thin film of a copper coordination polymer, Cu-BHT (BHT = benzenehexathiol), is prepared via a liquid-liquid interface reaction between BHT/dichloromethane and copper(II) nitrate/H2O. The morphology and structure characterization reveal that this film is piled up by nanosheets of 2D lattice of [Cu-3(C6S6)](n), which is further verified by quantum simulation. Four-probe measurements show that the room temperature conductivity of this material can reach up to 1,580 S cm (-1), which is the highest value ever reported for coordination polymers. Meanwhile, it displays ambipolar charge transport behaviour and extremely high electron and hole mobilities (99 cm(2) V (-1) s (-1) for holes and 116 cm(2) V (-1) s (-1) for electrons) under field-effect modulation.

528 citations


Journal ArticleDOI
TL;DR: This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.
Abstract: Facile postsynthetic oxidation of the thiol-laced UiO-66-type framework UiO-66(SH)2 enabled the generation of UiO-66(SO3H)2 with sulfonic acid groups covalently linked to the backbone of the system. The oxidized material exhibited a superprotonic conductivity of 8.4×10−2 S cm−1 at 80 °C and 90 % relative humidity, and long-term stability of the conductivity was observed. This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.

416 citations


Journal ArticleDOI
TL;DR: The surface plasmon modes of periodic hole arrays in Ag and Al films enhance by one order of magnitude the conductivity and the carrier mobility of organic semiconducting films deposited on these structures as mentioned in this paper.
Abstract: The surface plasmon modes of periodic hole arrays in Ag and Al films enhance by one order of magnitude the conductivity and the carrier mobility of organic semiconducting films deposited on these structures.

357 citations


Journal ArticleDOI
TL;DR: In this paper, two fundamentally different doping mechanisms are used to investigate the thermoelectric properties of known high hole mobility polymers: poly 3-hexylthiophene (P3HT), poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene) (PBTTT-C14), and poly(1.7-diheptadecantyltetrathienoacene)) (P2TDC17-FT4).
Abstract: The development of organic semiconductors for use in thermoelectrics requires the optimization of both their thermopower and electrical conductivity. Here two fundamentally different doping mechanisms are used to investigate the thermoelectric properties of known high hole mobility polymers: poly 3-hexylthiophene (P3HT), poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14), and poly(2,5-bis(thiphen-2-yl)-(3,7-diheptadecantyltetrathienoacene)) (P2TDC17-FT4). The small molecule tetrafluorotetracyanoquinodimethane (F4TCNQ) is known to effectively dope these polymers, and the thermoelectric properties are studied as a function of the ratio of dopant to polymer repeat unit. Higher electrical conductivity and values of the thermoelectric power factor are achieved by doping with vapor-deposited fluoroalkyl trichlorosilanes. The combination of these data reveals a striking relationship between thermopower and conductivity in thiophene-based polymers over a large range of electrical conductivity that is independent of the means of electrical doping. This relationship is not predicted by commonly used transport models for semiconducting polymers and is demonstrated to hold for other semiconducting polymers as well.

321 citations


Journal ArticleDOI
TL;DR: The transition metal-semiquinoid system is established as a particularly promising scaffold for achieving tunable long-range electronic communication in MOFs.
Abstract: A three-dimensional network solid composed of FeIII centers and paramagnetic semiquinoid linkers, (NBu4)2FeIII2(dhbq)3 (dhbq2–/3– = 2,5-dioxidobenzoquinone/1,2-dioxido-4,5-semiquinone), is shown to exhibit a conductivity of 0.16 ± 0.01 S/cm at 298 K, one of the highest values yet observed for a metal–organic framework (MOF). The origin of this electronic conductivity is determined to be ligand mixed-valency, which is characterized using a suite of spectroscopic techniques, slow-scan cyclic voltammetry, and variable-temperature conductivity and magnetic susceptibility measurements. Importantly, UV–vis–NIR diffuse reflectance measurements reveal the first observation of Robin–Day Class II/III mixed valency in a MOF. Pursuit of stoichiometric control over the ligand redox states resulted in synthesis of the reduced framework material Na0.9(NBu4)1.8FeIII2(dhbq)3. Differences in electronic conductivity and magnetic ordering temperature between the two compounds are investigated and correlated to the relative r...

298 citations


Journal ArticleDOI
TL;DR: Li et al. as mentioned in this paper applied density functional theory (DFT) to calculate the defect energies and site preference of all possible dopants in Li7La3Zr2O12 (LLZO) materials.
Abstract: Lithium garnet with the formula Li7La3Zr2O12 (LLZO) has many properties of an ideal electrolyte in all-solid state lithium batteries. However, internal resistance in batteries utilizing these electrolytes remains high. For widespread adoption, the LLZO’s internal resistance must be lowered by increasing its bulk conductivity, reducing grain boundary resistance, and/or pairing it with an appropriate cathode to minimize interfacial resistance. Cation doping has been shown to be crucial in LLZO to stabilize the higher conductivity cubic structure, yet there is still little understanding about which cations have high solubility in LLZO. In this work, we apply density functional theory (DFT) to calculate the defect energies and site preference of all possible dopants in these materials. Our findings suggest several novel dopants such as Zn2+ and Mg2+ predicted to be stable on the Li- and Zr-sites, respectively. To understand the source of interfacial resistance between the electrolyte and the cathode, we inves...

274 citations


Journal ArticleDOI
TL;DR: In this paper, the authors established a calculation model of the conductivity of multilayer graphene based on Boltzmann transport equation and 2D electron gas theory, and showed that the conductivities of few-layer graphene and graphene nanosheets are reduced when thickness is increased.

270 citations


Journal ArticleDOI
TL;DR: The results provide important insight for the rational design of conductive metal–organic frameworks, highlighting in particular the advantages of iron for synthesizing such materials.
Abstract: Reaction of FeCl2 and H4DSBDC (2,5-disulfhydrylbenzene-1,4-dicarboxylic acid) leads to the formation of Fe2(DSBDC), an analogue of M2(DOBDC) (MOF-74, DOBDC4– = 2,5-dihydroxybenzene-1,4-dicarboxylate). The bulk electrical conductivity values of both Fe2(DSBDC) and Fe2(DOBDC) are ∼6 orders of magnitude higher than those of the Mn2+ analogues, Mn2(DEBDC) (E = O, S). Because the metals are of the same formal oxidation state, the increase in conductivity is attributed to the loosely bound Fe2+ β-spin electron. These results provide important insight for the rational design of conductive metal–organic frameworks, highlighting in particular the advantages of iron for synthesizing such materials.

257 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the alignment of the O 2p valence bands and the unoccupied Co 3d conduction bands improves the conductivity of the La1-xSrxCoO3 perovskite series.
Abstract: The bulk electronic structure, surface composition, conductivity, and electrochemical activity toward the oxygen evolution reaction for the La1–xSrxCoO3 perovskite series (with x = 0, 0.2, 0.4, 0.6, 0.8, 1) are investigated experimentally and theoretically. It is found that Sr substitutions have the effect of straightening the octahedral cage, aligning atoms along the Co–O–Co axis, and increasing the average oxidation state of the Co cations. As a consequence, both the ex situ electronic conductivity as well as the activity toward the oxygen evolution reaction are considerably improved. According to density-functional theory calculations, the alignment of the Co–O–Co bonds and the oxidation of the Co cations enhance the overlap between the occupied O 2p valence bands and the unoccupied Co 3d conduction bands, rationalizing the improvement of the conductivity as a function of the Sr fraction. Additionally, a study of the surface properties as a function of the Sr fraction, carried out by X-ray photoelectro...

238 citations


Journal ArticleDOI
TL;DR: This work shows imidazole loaded tetrahedral polyimides with mesopores and good stability exhibiting a high anhydrous proton conductivity over a wide temperature range from -40 to 90 °C.
Abstract: On-board fuel cell technology requires proton conducting materials with high conductivity not only at intermediate temperatures for work but also at room temperature and even at subzero temperature for startup when exposed to the colder climate. To develop such materials is still challenging because many promising candidates for the proton transport on the basis of extended microstructures of water molecules suffer from significant damage by heat at temperatures above 80 °C or by freeze below -5 °C. Here we show imidazole loaded tetrahedral polyimides with mesopores and good stability (Im@Td-PNDI 1 and Im@Td-PPI 2) exhibiting a high anhydrous proton conductivity over a wide temperature range from -40 to 90 °C. Among all anhydrous proton conductors, the conductivity of 2 is the highest at temperatures below 40 °C and comparable with the best materials, His@[Al(OH)(1,4-ndc)]n and [Zn3(H2PO4)6(H2O)3](Hbim), above 40 °C.

215 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyzed the properties of Na superionic conductor (NASICON) materials in terms of their crystal structure, compositional diversity and ionic conductivity.

Journal ArticleDOI
TL;DR: The structural-chemical composition-ionic conductivity relationship of Li-stuffed garnets, followed by a discussion on the Li ion conduction mechanism, as well as the electrochemical and chemical stability of these materials are discussed.
Abstract: Lithium ion batteries are the most promising energy storage system on the market today; however, safety issues associated with the use of flammable organic polymer-based electrolytes with poor electrochemical and chemical stabilities prevent this technology from reaching maturity. Solid lithium ion electrolytes (SLIEs) are being considered as potential replacements for the organic electrolytes to develop all-solid-state Li ion batteries. Out of the recently discovered SLIEs, the garnet-related structured Li-stuffed metal oxides are the most promising electrolytes due to their high total (bulk + grain boundary) Li ion conductivity, high electrochemical stability window (∼6 V versus Li+/Li at room temperature), and chemical stability against reaction with an elemental Li anode and high-voltage metal oxide Li cathodes. This Perspective discusses the structural–chemical composition–ionic conductivity relationship of Li-stuffed garnets, followed by a discussion on the Li ion conduction mechanism, as well as th...

Journal ArticleDOI
TL;DR: In this paper, high conductivity nanocomposites of molybdenum disulfide (MoS2)/polyaniline (PANI) were prepared via direct intercalation of aniline monomer and doped with dodecyl benzene sulfonic acid (DBSA).


Journal ArticleDOI
TL;DR: It is shown that thermoelectric performance of PEDOT:PSS can be enhanced by greatly improving its electrical conductivity in contrast to inorganic thermoeLECTric materials.
Abstract: For inorganic thermoelectric materials, Seebeck coefficient and electrical conductivity are interdependent, and hence optimization of thermoelectric performance is challenging. In this work we show that thermoelectric performance of PEDOT:PSS can be enhanced by greatly improving its electrical conductivity in contrast to inorganic thermoelectric materials. Free-standing flexible and smooth PEDOT:PSS bulky papers were prepared using vacuum-assisted filtration. The electrical conductivity was enhanced to 640, 800, 1300, and 1900 S cm(-1) by treating PEDOT:PSS with ethylene glycol, polyethylene glycol, methanol, and formic acid, respectively. The Seebeck coefficient did not show significant variation with the tremendous conductivity enhancement being 21.4 and 20.6 μV K(-1) for ethylene glycol- and formic acid-treated papers, respectively. This is because secondary dopants, which increase electrical conductivity, do not change oxidation level of PEDOT. A maximum power factor of 80.6 μW m(-1) K(-2) was shown for formic acid-treated samples, while it was only 29.3 μW m(-1) K(-2) for ethylene glycol treatment. Coupled with intrinsically low thermal conductivity of PEDOT:PSS, ZT ≈ 0.32 was measured at room temperature using Harman method. We investigated the reasons behind the greatly enhanced thermoelectric performance.

Journal ArticleDOI
TL;DR: In this paper, the phase stability, dopant formation energy and Na+ conductivity of pristine and doped cubic Na3PS4 (c-Na3PS 4) were investigated.
Abstract: In this work, we performed a first-principles investigation of the phase stability, dopant formation energy and Na+ conductivity of pristine and doped cubic Na3PS4 (c-Na3PS4). We show that pristine c-Na3PS4 is an extremely poor Na ionic conductor, and the introduction of Na+ excess is the key to achieving reasonable Na+ conductivities. We studied the effect of aliovalent doping of M4+ for P5+ in c-Na3PS4, yielding Na3+xMxP1–xS4 (M = Si, Ge, and Sn with x = 0.0625; M = Si with x = 0.125). The formation energies in all the doped structures with dopant concentration of x = 0.0625 are found to be relatively low. Using ab initio molecular dynamics simulations, we predict that 6.25% Si-doped c-Na3PS4 has a Na+ conductivity of 1.66 mS/cm, in excellent agreement with previous experimental results. Remarkably, we find that Sn4+ doping at the same concentration yields a much higher predicted Na+ conductivity of 10.7 mS/cm, though with a higher dopant formation energy. A higher Si4+ doping concentration of x = 0.125...

Journal ArticleDOI
TL;DR: In this paper, a two-scale composite model consisting of graphene-rich regions serving as the agglomerates and a graphene-poor region as the matrix is presented, and the effective medium theory is introduced to determine the percolation threshold and electrical conductivity of the agglerate and the composite.
Abstract: The dispersion state or degree of agglomeration of graphene is known to have a significant influence on the percolation threshold and electrical conductivity of graphene-based polymer nanocomposites. In addition, an imperfectly conducting interface and tunneling-assisted interfacial conductivity can also affect the overall conductivity. In this paper, a continuum theory is developed that considers all these factors. We first present a two-scale composite model consisting of graphene-rich regions serving as the agglomerates and a graphene-poor region as the matrix. We then introduce the effective-medium theory to determine the percolation threshold and electrical conductivity of the agglomerate and the composite. To account for the effect of imperfect interfaces, a thin layer of interphase with low conductivity is introduced to build a thinly coated graphene, while to account for the contribution of electron hopping from one graphene to another, Cauchy's statistical function which can reflect the increased...

Journal ArticleDOI
TL;DR: In this article, it was shown that confining LiBH4 in the pores of ordered mesoporous silica scaffolds leads to high Li+ conductivity (0.1 mS cm(-1)) at room temperature.
Abstract: Designing new functional materials is crucial for the development of efficient energy storage and conversion devices such as all solid-state batteries. LiBH4 is a promising solid electrolyte for Li-ion batteries. It displays high lithium mobility, although only above 110 degrees C at which a transition to a high temperature hexagonal structure occurs. Herein, it is shown that confining LiBH4 in the pores of ordered mesoporous silica scaffolds leads to high Li+ conductivity (0.1 mS cm(-1)) at room temperature. This is a surprisingly high value, especially given that the nanocomposites comprise 42 vol% of SiO2. Solid state Li-7 NMR confirmed that the high conductivity can be attributed to a very high Li+ mobility in the solid phase at room temperature. Confinement of LiBH4 in the pores leads also to a lower solid-solid phase transition temperature than for bulk LiBH4. However, the high ionic mobility is associated with a fraction of the confined borohydride that shows no phase transition, and most likely located close to the interface with the SiO2 pore walls. These results point to a new strategy to design low-temperature ion conducting solids for application in all solid-state lithium ion batteries, which could enable safe use of Li-metal anodes.

Journal ArticleDOI
TL;DR: The highly unique crystal structure of the metal-organic framework (MOF) zirconium 2-sulfoterephthalate is presented, which contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material.
Abstract: Understanding the role that crystal imperfections or defects play on the physical properties of a solid material is important for any application. In this report, the highly unique crystal structure of the metal-organic framework (MOF) zirconium 2-sulfoterephthalate is presented. This MOF contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material. The partially occupied ligand positions give rise to a continuum of pore sizes within this highly porous MOF, supported by N2 gas sorption and micropore analysis. Furthermore, this MOF is lined with sulfonic acid groups, implying a high proton concentration in the pore, but defective zirconium clusters are found to be effective proton trapping sites, which was investigated by a combination of AC impedance analysis to measure the proton conductivity and DFT calculations to determine the solvation energies of the protons in the pore. Based on the calculations, methods to control the pKa of the clusters and improve the conductivity by saturating the zirconium clusters with strong acids were utilized, and a 5-fold increase in proton conductivity was achieved using these methods. High proton conductivity of 5.62 × 10(-3) S cm(-1) at 95% relative humidity and 65 °C could be achieved, with little change down to 40% relative humidity at room temperature.

Journal ArticleDOI
TL;DR: In this paper, the electrical and dielectric parameters of the nanocomposite solid polymer electrolyte (SPE) films were investigated using electrical impedance spectroscopy, and the relationship between the two parameters was analyzed to understand the ion-conduction mechanism.
Abstract: In this study, (1.1111 - x)(0.9CS-0.1NaTf)-xAl(2)O(3)(0.02 <= x <= 0.1) [where CS is chitosan, NaTf is sodium triflate (NaCF3SO3), and Al2O3 is aluminum oxide] nanocomposite solid polymer electrolyte (SPE) films based on CS were prepared by a solution casting technique. X-ray diffraction and scanning electron microscopy analysis revealed that the alumina nanoparticles had a great effect on the structural and morphological behavior of the CS-NaTf (90:10) polymer electrolyte. An investigation of the electrical and dielectric parameters of the nanocomposite SPE films was conducted. Electrical impedance spectroscopy was carried out for this purpose. The relationships between the electrical and dielectric parameters were used to interpret and understand the ion-conduction mechanism. We observed that the direct-current conductivity (sigma(dc)) and dielectric constant followed the same trend with salt concentration. sigma(dc) versus temperature showed the Arrhenius and Vogel-Fulcher-Tammann (VTF) regions. The drops of sigma(dc) at high temperatures were observed for all of the samples. The ion relaxation dynamics were studied from Argand plots. For the first time, we confirmed the existence of a strong experimental relationship between the high-frequency semicircle of the impedance plots and the high-frequency dispersion regions of the alternating-current conductivity (sigma(ac)). The dispersion regions of sigma(ac) were used to study the ion-conduction mechanism. The behavior of the frequency exponent as a function of the temperature was used to interpret sigma(dc) versus the temperature. (C) 2014 Wiley Periodicals, Inc.

Journal ArticleDOI
TL;DR: In this article, the authors presented the synthesis of highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) based polymers using iron(III) trifluoromethanesulfonate as oxidant for the first time.
Abstract: Conductive polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) are used in a wide range of applications as transparent electrodes, hole injecting layers or thermoelectric materials for room-temperature applications. However, progress is needed to enhance the electrical conductivities of the materials and to provide understanding about their structure–transport relationships. This work presents the synthesis of highly conductive PEDOT-based polymers using iron(III) trifluoromethanesulfonate as oxidant for the first time. The metallic behaviour of the polymer is revealed by conductivity monitoring from 3 to 300 K. The electrical conductivity is further improved (to 2273 S cm−1) using acids, leading to a positive temperature coefficient of resistivity at an unprecedented 45.5% oxidation state. X-ray photoemission spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS) analyses demonstrate a complete replacement of the trifluoromethanesulfonate anions by hydrogen sulphate counter ions. This substitution results in an increased concentration of charge carriers (measured in organic electrochemical transistors) along with an enhancement of the mean size of crystalline domains, highlighted by small and wide angle X-ray scattering (SAXS/WAXS), which explains the 80% increase of electrical conductivity.

Journal ArticleDOI
TL;DR: A transparent garnet-type lithium-ion conducting solid electrolyte of 1.0% Al 2 O 3 -doped Li 7 La 3 Zr 2 O 12 (A-LLZ) was prepared using hot isostatic pressing (HIP) as discussed by the authors.

Journal ArticleDOI
TL;DR: An exceptionally high chemical stability in reducing conditions and redox cycles at high temperature, usually unattainable for Bi2O3-based materials, is achieved and at low oxygen partial pressure the layered material shows anomalous high conductivity, equal or superior to pure δ-Bi2O2 in air.
Abstract: Bismuth-oxide-based materials are the building blocks for modern ferroelectrics, multiferroics, gas sensors, light photocatalysts and fuel cells. Although the cubic fluorite δ-phase of bismuth oxide (δ-Bi2O3) exhibits the highest conductivity of known solid-state oxygen ion conductors, its instability prevents use at low temperature. Here we demonstrate the possibility of stabilizing δ-Bi2O3 using highly coherent interfaces of alternating layers of Er2O3-stabilized δ-Bi2O3 and Gd2O3-doped CeO2. Remarkably, an exceptionally high chemical stability in reducing conditions and redox cycles at high temperature, usually unattainable for Bi2O3-based materials, is achieved. Even more interestingly, at low oxygen partial pressure the layered material shows anomalous high conductivity, equal or superior to pure δ-Bi2O3 in air. This suggests a strategy to design and stabilize new materials that are comprised of intrinsically unstable but high-performing component materials.

Journal ArticleDOI
TL;DR: In this article, the Li site occupancy in cubic garnet was studied as a function of Li concentration over the compositions range: Li 7− x La 3 Zr 2−x Ta x O 12 (x = 0.5, 0.75, and 1.5).
Abstract: Solid electrolytes based on the garnet crystal structure have recently been identifi ed as a promising material to enable advance Li battery cell chemistries because of the unprecedented combination of high ionic conductivity and electrochemical stability against metallic Li. To better understand the mechanisms that give rise to high conductivity, the goal of this work is to correlate Li site occupancy with Li-ion transport. Toward this goal, the Li site occupancy is studied in cubic garnet as a function of Li concentration over the compositions range: Li 7− x La 3 Zr 2− x Ta x O 12 ( x = 0.5, 0.75, and 1.5). The distribution of Li between the two interstitial sites (24d and 96h) is determined using neutron and synchrotron diffraction. The bulk conductivity is measured on >97% relative density polycrystalline specimens to correlate Li-ion transport as a function of Li site occupancy. It is determined that the conductivity changes nonlinearly with the occupancy of the octahedral (96h) Li site. It is shown that the effective carrier concentration is dependent on the Li site occupancy and suggests that this is a consequence of signifi cant carrier‐ carrier coulombic interactions. Furthermore, the observation of maximum conductivity near Li = 6.5 mol is explained.

Journal ArticleDOI
TL;DR: In this article, a starch-chitosan blend based solid polymer electrolyte (SPE) system and its application in electrochemical double layer capacitor (EDLC) and proton batteries are reported.

Journal ArticleDOI
TL;DR: In this article, the ratio of thermal conductivities and electrical conductivities of nanofluids in water: ethylene glycol (EG) mixtures are established. But, the results showed that thermal conductivity reduced as the EG content percentage increases in the water: EG mixture.

Journal ArticleDOI
TL;DR: A practical geometry for device miniaturization is created, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3 and it is shown that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm- doped Ce O2 nanopillars.
Abstract: Enhancement of oxygen ion conductivity in oxides is important for low-temperature (<500 °C) operation of solid oxide fuel cells, sensors and other ionotronic devices. While huge ion conductivity has been demonstrated in planar heterostructure films, there has been considerable debate over the origin of the conductivity enhancement, in part because of the difficulties of probing buried ion transport channels. Here we create a practical geometry for device miniaturization, consisting of highly crystalline micrometre-thick vertical nanocolumns of Sm-doped CeO2 embedded in supporting matrices of SrTiO3. The ionic conductivity is higher by one order of magnitude than plain Sm-doped CeO2 films. By using scanning probe microscopy, we show that the fast ion-conducting channels are not exclusively restricted to the interface but also are localized at the Sm-doped CeO2 nanopillars. This work offers a pathway to realize spatially localized fast ion transport in oxides of micrometre thickness.

Journal ArticleDOI
TL;DR: In this paper, the authors reported some physical properties of AgAlP2O7 compound obtained through the standard solid-state reaction technique and studied the electrical properties over a wide range of temperature (440-640 k) in the frequency range of 40-10MHz.
Abstract: In this paper, we report some physical properties of AgAlP2O7 compound obtained through the standard solid-state reaction technique. AgAlP2O7 has been studied by X-ray diffraction, Raman spectroscopy and impedance spectroscopy. The title compound crystallized at room temperature (T = 300 K) in the monoclinic system with P21/c space group. The electrical properties were studied over a wide range of temperature (440–640 K) in the frequency range of 40 Hz–10 MHz. Study of frequency dependence of AC conductivity suggests that the material obeys the Jonscher’s universal dynamic law. The conductivity is equal to 9.37 × 10−5 Ω cm−1 at 640 K, and it is thermally activated with activation energy of 0.76 eV. The variation of DC conductivity with temperature follows the Arrhenius behavior. The calculated values of s decreased with temperature. This behavior reveals that the conduction mechanism is correlated with barrier hopping. The binding energy W m and the hopping distance R ω were deduced.

Journal ArticleDOI
TL;DR: In this paper, a solid polymer electrolyte (SPE) was prepared by a ball milling method followed by a hot pressing process, and the morphology, ionic conductivity, thermal and mechanical properties of the SPE were also examined.

Journal ArticleDOI
Wenxia Sima1, Jian Shi1, Qing Yang1, Sisi Huang1, Xue-Fei Cao1 
TL;DR: In this paper, the potential well distribution of surface and saturation charges on conductive and dielectric NPs is analyzed and compared with those of pure oil-based NPs.
Abstract: The mechanisms by which conductive and dielectric nanoparticles (NPs) trap electrons are explained by the potential well distribution caused by induced or polarized charges on NPs. Thus, the distributions of surface and saturation charges on conductive and dielectric NPs are determined. Given conductive Fe3O4, semiconductive TiO2, and dielectric Al2O3 NPs, insulation performance tests are conducted and ionization models of nanofluids (NFs) based on transformer oil are developed. These models are compared with those of NFs based on pure oil. The NP whose conductivity or permittivity does not match that of the dielectric liquid has a potential well and an increased amount of saturation charges on its interface. This NP influences streamer development strongly and enhances the breakdown of oilbased NF.