Electrical Conductivity of Synthetic Crystalline Zeolites

Freeman, Donald C.; Stamires, Dennis N.

doi:10.1063/1.1701219

Cited by 150 publications

(70 citation statements)

References 7 publications

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“…By irradiation of zeolites and zeolite-like materials, it is possible to change their granular structure, to form non-equilibrium electrons and holes, and different type of radicals on the samples surface [23,24]. All listed processes may result in a change of parameters for electrical-carrier transport of zeolite, such as concentration of protons and their mobility, length of free path of charge carriers (various ions), and polarization of the crystal cage [20,25]. Fig.…”

Section: Specific Conductivitymentioning

confidence: 99%

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Dielectric properties and specific conductivity of armenian natural clinoptilolite irradiated by electrons

et al. 2005

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Abstract:The results of dielectric properties and direct current specific electric conductivity measurements in Armenian natural clinoptilolite samples are presented. Electron irradiation with energy 8 MeV and thermal treatment of samples are performed to elucidate possible enhancement mechanisms of clinoptilolite parameters. The results are discussed on the basis of new point structural defects formation and recombination of initial ones in samples. It was shown that the irradiation dose of 3·10 16 el/cm 2 is critical for natural zeolite structural change, which is manifested by significant changes in dielectric properties and other characteristics. The samples subjected to high temperature heating after electron irradiation, in comparison with an unquenched one, have a significantly higher (about an order of magnitude) value of specific conductivity.

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Section: Specific Conductivitymentioning

confidence: 99%

“…The main reason for such relaxation is the polarization of a sample, which is taken into account by a method described in refs. [17][18][19][20].…”

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confidence: 99%

Dielectric properties and specific conductivity of armenian natural clinoptilolite irradiated by electrons

et al. 2005

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“…Similar behavior is to be expected in the variation with Al-content of the thermal stability of the NH4*-exchanged faujasite series. Stamires (1960Stamires ( , 1962; Freeman and Stamires (1961 );Schoonheydt and Uytterhoeven (1969) have shown that the current-carrying species in synthetic zeolites are cations migrating in the structure by a "jump" mechanism. Further, the activation energy for conduction is due to the electrostatic interaction of the cation with its site in the alumino--silicate framework.…”

Section: Mechanism Of Structural Degradation By Steamingmentioning

confidence: 99%

Properties of the Zeolite, Faujasite, Substitutional Series: A Review with New Data

Stamires¹

1973

Clays and clay miner.

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Abstract--New information is presented relating to the hydrothermal stability, lattice parameters, and adsorptive, electrical, and catalytic properties of synthetic and natural faujasite. Present concepts concerning the nature and relationship of synthetic and natural faujasite are restated to be consistent with the experimental evidence and the developed physical model. The major structural and physicochemical properties reflect the close similarities and smooth gradations expected of substitutional members of a continuous series. The existing division of the range (2-6) of SiO2/A1203 mole ratios (S/A) at 3 into two compositional subranges is shown to be unjustifiable and rather misleading. Individual compositions from these two subranges do not represent distinctly different zeolite species; instead, it is demonstrated that they are members of a continuous series with smoothly changing properties over the studied range of SiO2/AI~O3. Some of the properties of the natural mineral faujasite are found to be very similar to those of the synthetic analogs with the same SiO2/A1203 mole ratio.Finally, a plea is made for a uniform nomenclature which will serve to identify specific (single) compositions (instead of ranges of compositions); reflect the continuity, close similarities and interrelationships in their main structural and physicochemical properties; and also identify the characteristics of the faujasite group. INTRODUCTION HISTORICALLY, experimental work on crystalline aluminosilicates of the faujasite type started when Damour (1848) published a chemical analysis of faujasite. Synthetic zeolites designated as X and Y were produced by Milton (1959) and Breck (1964). The X-ray work of Baur (1964), Bergerhoff et al. (1956) and Broussard and Shoemaker (1960) and the adsorption studies of Barrer et al. (1957) established the structural identities of these synthetic zeolites and the natural mineral. However, the location of certain cations in the aluminosilicate framework and the relative degree of (Si, A1) ordering in the lattice still remain uncertain and may be different in the synthetic and natural species.It is possible to synthesize hydrothermally a continuous series of faujasite zeolites with uniform compositional wariation. Breck (1964) has divided this series into two compositional ranges, one a high alumina species designated as type X, the other a high silica species designated as type Y. Over the entire silica-alumina range from 2--6, the unit cell dimensions for zeolites in both ranges were found (Breck arid Flanigen, 1968) to vary linearly

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“…Ducros and Rimsky (176) claim that the Ca++ ions in hydrated natural chabazite are situated near the centres of the hexagonal prisms at the top and bottom of each cage, They were unable to place the This is probably due to the additional loss contribution from the increased number of water molecules, to the lowering of the energy barrier to cation migration and to a wider distribution of relaxation times. It is (160,161,165,168) …”

Section: Use Of Bottoberis Equationmentioning

confidence: 99%