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Conductivity of Mono- and Divalent Cations in the Microporous Zincosilicate VPI-9

McKeen, John C. and Davis, Mark E. (2009) Conductivity of Mono- and Divalent Cations in the Microporous Zincosilicate VPI-9. Journal of Physical Chemistry C, 113 (22). pp. 9870-9877. ISSN 1932-7447. doi:10.1021/jp902235z. https://resolver.caltech.edu/CaltechAUTHORS:20090901-142619577

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Abstract

Impedance spectroscopy is used to investigate the long-range ionic conductivity of the microporous, zincosilicate VPI-9 (Si/Zn = 4.0) (International Zeolite Association framework type VNI) containing the alkali cations Li^+, Na^+, K^+, Rb^+, and Cs^+, and the alkaline earth cations Mg^(2+), Ca^(2+), and Sr^(2+). Monovalent cation-exchanged samples Li- and Na-VPI-9 lose X-ray crystallinity upon vacuum dehydration at 450 °C, whereas K-, Rb-, and Cs-VPI-9 remain crystalline and exhibit conductivities of 1.7 × 10^(−4), 3.5 × 10^(−4), and 4.9 × 10^(−4) S/cm, respectively, at 450 °C and activation energies of 0.72, 0.64, and 0.69 eV, respectively, in the temperature range 150−450 °C. Divalent cation-exchanged sample Mg-VPI-9 also loses X-ray crystallinity, but Ca- and Sr-VPI-9 remain crystalline and exhibit conductivities of 2.3 × 10^(−6) S/cm and 7.7 × 10^(−7) S/cm, respectively, at 450 °C, and activation energies of 0.88 and 0.91 eV, respectively, over the temperature range 150−450 °C. When compared to aluminosilicate zeolite X (Si/Al = 1.25) exchanged with the same cations, all crystalline M-VPI-9 materials have greater conductivities than M-X, with the exception of K-X (1.6 × 10^(−3) S/cm at 450 °C), with the greatest differences arising between the divalent exchanged materials. Dense, crystalline zincosilicate samples with the compositions K_2ZnSi_xO_(2(x+1)) (x = 2−5), Rb_2ZnSi_5O_(12), and Cs_2ZnSi_5O_(12) are also prepared and characterized for comparison with the microporous materials and exhibit much lower conductivities than their microporous counterparts at the same composition.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/jp902235zDOIUNSPECIFIED
http://pubs.acs.org/doi/abs/10.1021/jp902235zPublisherUNSPECIFIED
ORCID:
AuthorORCID
Davis, Mark E.0000-0001-8294-1477
Additional Information:Copyright © 2009 American Chemical Society. Received: March 12, 2009; Revised Manuscript Received: April 21, 2009. Publication Date (Web): May 12, 2009. J.C.M. acknowledges the Fannie and John Hertz Foundation and the National Science Graduate Research Fellowship Program for financial support. Supporting Information: A photograph of the experimental apparatus along with modulus spectra from sodium exchanged zeolite X and discussion thereof are provided in the Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org.
Funders:
Funding AgencyGrant Number
Fannie and John Hertz FoundationUNSPECIFIED
NSFUNSPECIFIED
Issue or Number:22
DOI:10.1021/jp902235z
Record Number:CaltechAUTHORS:20090901-142619577
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20090901-142619577
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15533
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:09 Sep 2009 18:14
Last Modified:08 Nov 2021 23:20

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