Electrical conductivity in iron-containing oxide glasses

Murawski, L.

doi:10.1007/bf00543723

Cited by 89 publications

(39 citation statements)

References 34 publications

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“…Since the charge carrier concentrations are related to the iron ion content, the decrease in s dc is attributed to a decrease in the number of carriers with decreasing iron content. These results agree with previously reported ones [33][34][35] where s dc for alkaline earth-free iron phosphate glasses is attributed to the migration of polarons and charge transport can be visualized as carriers hopping a distance between the phosphate chains. The hopping conductivity depends upon the distance between iron ions and the conductivity is less than that in ionic conductive glass [32].…”

Section: Conductivity and Activation Energysupporting

confidence: 83%

Electrical Conductivity in Mixed Calcium and Barium Iron Phosphate Glasses

El‐Desoky

Kashif

2002

phys. stat. sol. (a)

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The electrical properties of xCaO–(20 — x)BaO–20Fe2O3–60P2O5 glasses with x = 0, 5, 10, 15 and 20 mol% have been studied in the frequency range 400 Hz–200 kHz and over a temperature range 323–593 K. The ac conductivity as a function of temperature was divided into two domains, one where the absolute magnitude of the ac conductivity was close to the dc conductivity and another where it was larger than the dc conductivity. At the same temperature, the dc conductivity varied only slightly in glasses with different CaO and BaO content. It is concluded that the conductivity in these mixed CaO and BaO iron phosphate glasses is electronic and depends upon the Fe2+/(Fe2+ + Fe3+) ratio. In the high‐temperature region above θD/2 (where θD is the Debye temperature) the Mott model of small polaron hopping (SPH) between nearest neighbours is consistent with the conductivity data, while at low temperature (below θD) the Greaves intermediate variable‐range hopping (VRH) model is found to be appropriate. The electrical conduction of the glasses is confirmed to be non‐adiabatic SPH. Mössbauer spectral analysis indicates the presence of both Fe2+ and Fe3+ ions.

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Section: Conductivity and Activation Energysupporting

confidence: 83%

Electrical Conductivity in Mixed Calcium and Barium Iron Phosphate Glasses

El‐Desoky

Kashif

2002

phys. stat. sol. (a)

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“…For instance, E a =0.61 ±0.03 eV in binary iron phosphate xP 2 O 5 -(1−x)FeO, for any x in the range 40-55 mol% investigated [21]. The value E a =0.65±0.05 eV relevant to LiFePO 4 also applies to (50−x)FeO-50 P 2 O 5 -xBaO in the range of composition that has been explored (10≤x≤35 mol%) [20] and also where the modifier BaO is replaced by CaO or by Na 2 O [21]. We can then conclude that this value of E a is a property characteristic of the Fe 2+ /Fe 3+ redox couple in a phosphate, which entirely determines the ability of the small polaron to hop to a neighbouring site.…”

Section: Electronic Propertiesmentioning

confidence: 92%

“…The electronic conductivity of these glasses is the archetype of small-polaron hopping [20] that also results from the transfer of an electron between Fe 2+ and Fe 3+ as in LiFePO 4 . The remarkable feature of all these iron phosphate glasses is that E a is about the same as in LiFePO 4 .…”

Section: Electronic Propertiesmentioning

confidence: 99%

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Small magnetic polaron effect in lithium iron phosphates

Mauger

Zaghib

Giligny

et al. 2007

Ionics

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International audienceThe small polarons in LiFePO4 are associated with the presence of Fe3+ ions introduced by the native defects in relative concentration [Fe3+]/[Fe2+ + Fe3+] 3 x 10(-3) in the samples known to be optimized with respect to their electrochemical properties. The nearest iron neighbours around the central polaron site are spin-polarized by the indirect exchange mediated by the electronic charge in excess. These small magnetic polarons are responsible for the interplay between electronic and magnetic properties that are quantitatively and self-consistently analysed. Comparison is made with other magnetic polaron effects in other members of the family of magnetic semiconductors to which this material belongs

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“…In this hopping process, in which the hole is in a bound polaron state with the same energy after and before the hop, the activation energy is simply the energy barrier that the hole has to overcome to jump to the next site. This is much less than the binding energy required to send a d-electron from an Fe 2+ valence band to the conduction band, an energy of 0.65 eV that is typical of the hopping process in iron systems [10,11]. Nevertheless, this activation energy is still too large, and thus the electronic mobility is too small, to envision the use of LiFePO 4 as a cathode for Li-ion batteries with bare particles.…”

Section: Introductionmentioning

confidence: 96%

Overview of olivines in lithium batteries for green transportation and energy storage

Zaghib

Mauger

Julien

2012

J Solid State Electrochem

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We present the progress on the physical chemistry of the olivine compounds since the pioneering work of Prof. John Goodenough. This progress has allowed LiFePO 4 to become the active cathode element of a new generation of Li-ion batteries that makes a breakthrough in the technology of the energy storage and electric transportation. This achievement is the fruit of about a decade of intensive research in the electrochemical community during which chemists, electrochemists, and physicists added there efforts to understand the properties of the material, to overcome the obstacles that were met on the way, and finally to reach the state of the art that allows its commercial use for worldwide applications in the industry today. These obstacles involved carbon coating, purification, control of the surface, the progressive decrease of the size of the particles down to nanoscale, and comprehensive investigation of surface effects. Nevertheless, heterogeneity in the quality of the product available on the market is damaging and may even be an obstacle to the development of new demanding technologies such as electric transportation. Emphasis is placed on the quality control that is needed to guarantee the reliability and the optimum electrochemical performance of this material as the active cathode element of Li-ion batteries. The route to increase the performance of Li-ion batteries with the other members of the family is also discussed. Since Prof. John Goodenough not only initiated the work but also played a major role in the research and development on these materials through the years, the present review is dedicated to him.

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Electrical conductivity in iron-containing oxide glasses

Cited by 89 publications

References 34 publications

Electrical Conductivity in Mixed Calcium and Barium Iron Phosphate Glasses

Electrical Conductivity in Mixed Calcium and Barium Iron Phosphate Glasses

Small magnetic polaron effect in lithium iron phosphates

Overview of olivines in lithium batteries for green transportation and energy storage

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