Dielectric Loss and Hydration of Sodium Chabazite

Barrer, R. M.; Coen, P. J.

doi:10.1038/199587a0

Cited by 6 publications

(2 citation statements)

References 5 publications

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“…However, after dehydration, it is expected that any measured conductivity will be due to the migration of interstitial cations, commonly alkali metal or alkaline earth metal cations [19][20][21]. This migratory cation behavior is also expected to occur in chabazite, however, to the best of the authors' knowledge, few studies of the electrical properties of chabazites have been published [22][23][24][25]. For example, Beattie [20] examined a range of ion-exchanged chabazites based on the natural mineral of chabazite since it could not be synthesized at that time and an increase in activation energy with increasing ionic radii was observed, which ranged from ~0.65 to 0.8 eV [20].…”

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confidence: 99%

Understanding the AC conductivity and permittivity of trapdoor chabazites for future development of next-generation gas sensors

Bordeneuve

Wales

Physick

et al. 2018

Microporous and Mesoporous Materials

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Synthetic K + chabazite (KCHA), Cs + chabazite (CsCHA) and Zn 2+ chabazite (ZnCHA) have been synthesized and investigated in order to relate the differences in their crystalline structures to their thermal stability, moisture content and frequency dependent alternating current (AC) conductivity, permittivity and phase angle at a range of temperatures. The materials are shown to exhibit the universal dielectric response, which is typical of materials consisting of both conductive and insulating regions. Due to the presence of porosity the three chabazites were hydrated significantly at room temperature and so the dehydrated state was achieved by heating the chabazites to high temperatures to ensure that all different energetic types of water were removed. Cation migration activation energies for KCHA (0.66 ± 0.10) eV, CsCHA (0.88 ± 0.01) eV and ZnCHA (0.90 ± 0.01) eV were determined during the cooling cycle from the fully dehydrated state to provide an accurate measurement the activation energies. Good thermal stability of the materials was observed up to 710 °C and below 200 °C the electrical properties can be strongly influenced by hydration level. Overall, it was determined that when either hydrated or dehydrated, KCHA had the highest conductivity and lowest cation migration activation energy of the three studied chabazites and thus has the most promising electrical properties for potential use as a gas sensing material in next-generation electrical-based gas sensors.

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Section: Position Of Caption For Figure 1a and 1bmentioning

confidence: 99%

Understanding the AC conductivity and permittivity of trapdoor chabazites for future development of next-generation gas sensors

Bordeneuve

Wales

Physick

et al. 2018

Microporous and Mesoporous Materials

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“…Movements of an extra framework cation in a zeolite directly relate to its electric and dielectric properties and an interaction with microwaves. − Hence, in order to understand and use these properties and phenomena, it is necessary to elucidate and grasp the movements and behaviors of the cation. One way to elucidate them is to apply theoretical methods.…”

Section: Introductionmentioning

confidence: 99%

Relaxation Theory for Sodium Ion in Dehydrated Na-A Zeolite (LTA) and Elucidation of Ion Movements

Ohgushi

2007

J. Phys. Chem. C

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In order to elucidate details of relaxations caused by the sodium ion in dehydrated Na-A zeolite, a simplified jump model was constructed for the sodium ion on site 3, Na + /S3. In the model, Na + /S3 was set up to jump around among three adjacent unequivalent sites, that is, S3, a position in (or near) the 8-ring (S2′) and a position near the 6-ring (S1′). A relaxation theory was developed for the model. The equations derived showed that the relaxations were expressed with two relaxation times, τ, which related to transition frequencies of S3 T S2′ and S3 T S1′. In order to obtain a clear picture of relaxations, the expressions of τ were approximated and simplified. The simplified expressions clearly indicated that the relaxations observed at the lower and higher frequency sides mainly reflect the jumps of the sodium ion from S2′ to S3 and from S1′ to S3, respectively. Therefore, the concrete meaning of activation energy determined experimentally was also elucidated; the activation energies for the relaxations at the lower and higher frequency sides reflect the heights of the potential barrier in jumps from S2′ to S3 and from S1′ to S3, respectively. The transition frequencies for both jumps were calculated based on the measured frequencies of loss peaks. The validities of relationships used for approximation of τ were examined by using the calculated transition frequencies and were confirmed to be fully satisfied in the concerned temperature range (300-550 K). It is the first time that the relaxations in zeolite with a complicated configuration of cations and their sites are theoretically and minutely analyzed.

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The mobility of water in zeolites—II

Dyer

Molyneux

1968

Journal of Inorganic and Nuclear Chemistry

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Dielectric Loss and Hydration of Sodium Chabazite

Cited by 6 publications

References 5 publications

Understanding the AC conductivity and permittivity of trapdoor chabazites for future development of next-generation gas sensors

Understanding the AC conductivity and permittivity of trapdoor chabazites for future development of next-generation gas sensors

Relaxation Theory for Sodium Ion in Dehydrated Na-A Zeolite (LTA) and Elucidation of Ion Movements

The mobility of water in zeolites—II

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