DOI: 10.1126/science.1083842. High-Density Electron Anions in a Nanoporous Single Crystal: [Ca 24 Al 28 O 64 ] 4 + (4 e - )

High-Density Electron Anions in a Nanoporous Single Crystal: [Ca 24 Al 28 O 64 ] 4 + (4 e - )

10.1126/science.1083842

Crossref journal-article

American Association for the Advancement of Science (AAAS)

Science (221)

Abstract

We removed ∼100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO·7Al 2 O 3 , leading to the formation of high-density (∼2 × 10 21 cm – 3 ) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an F + center and migrates throughout the crystal by hopping to a neighboring cage with conductivity ∼100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca 24 Al 28 O 64 ] 4 + (4 e – ) may be regarded as a thermally and chemically stable single crystalline “electride.”

Bibliography

Matsuishi, S., Toda, Y., Miyakawa, M., Hayashi, K., Kamiya, T., Hirano, M., Tanaka, I., & Hosono, H. (2003). High-Density Electron Anions in a Nanoporous Single Crystal: [Ca 24 Al 28 O 64 ] 4 + (4 e - ). Science, 301(5633), 626â629.

Authors 8

Satoru Matsuishi (first)
Yoshitake Toda (additional)
Masashi Miyakawa (additional)
Katsuro Hayashi (additional)
Toshio Kamiya (additional)
Masahiro Hirano (additional)
Isao Tanaka (additional)
Hideo Hosono (additional)

References 28 Referenced 789

J. L. Dye, Inorg. Chem. 36, 3817 (1997). / Inorg. Chem (1997)
10.1103/PhysRevLett.80.2449
10.1021/ar950152c
10.1021/ja016554z
H. Bartl, T. Scheller, Neues Jahrb. Mineral. Monatshefte35, 547 (1970). / Neues Jahrb. Mineral. Monatshefte (1970)
10.1016/0008-8846(71)90083-4
10.1111/j.1151-2916.1964.tb15669.x
10.1021/ic00255a003
10.1021/ja016112n
10.1038/nature01053
10.1080/00018736800101386
10.1002/adma.200304925
We used C12A7 single crystals grown by the floating zone method ( 18 ) as starting material. These were sliced into 0.4-mm-thick plates and polished.
After the Ca treatment the inner surface of the glass tubes resembled a mirror owing to the formation of a metal calcium layer on the glass wall. However the surfaces of the C12A7 crystals remained transparent.
The CaO layer was transparent when the sample was sealed inside the tube but turned white within a few days after the seal was broken owing to the formation of CaCO 3 and Ca(OH) 2 by reaction with CO 2 and H 2 O in air.
A cross section of the treated sample gives a homogeneous color within the thickness used in the experiment which guarantees the accuracy of the present measurements and calculations. This is a reasonable supposition because C12A7 is a fast O 2 – ion conductor at high temperatures ( 17 ) and the extraction of free O 2 – ions is controlled by surface reactions between a C12A7 crystal and the metallic Ca layer formed.
10.1038/332525a0
S. Watauchi, I. Tanaka, K. Hayashi, M. Hirano, H. Hosono, J. Cryst. Growth237, 496 (2002). / J. Cryst. Growth (2002)
The absorption edge of stoichiometric C12A7 is ∼5 eV. However the as-grown single crystal contains O 2 – (4 × 10 18 cm – 3 ) that gives an absorption band peaking at 5 eV. Thus the apparent absorption edge is shifted to ∼4 eV.
According to a quantum-chemical calculation based on the embedded cluster model for UV-illuminated C12A7:H ( 21 ) an electron trapped in the cage is localized in the cage at the ground state and the 0.4- and 2.8-eV bands are due to the electronic transition to an adjacent cage and s→p excitation within the cage respectively. This result also provides a model in which the transfer of the clathrated electron is controlled by polaron associated with the 0.4-eV optical absorption band.
P. Sushko K. Schluger K. Hayashi M. Hirano H. Hosono in preparation.
In the polaron model the barrier height for thermal hopping to a nearest site is about four times as large as that for hopping by optical excitation. The latter is calculated to be 0.4 eV ( 21 ) and the thermal barrier height is predicted to be ∼0.16 eV.
N. F. Mott E. A. Davis Electronic Processes in Non-Crystalline Materials (Oxford Univ. Press Oxford ed. 2 1979).
10.4028/www.scientific.net/MSF.321-324.198
Fachinformationszentrum Karlsruhe and the National Institute of Standards and Technology (FIZ/NIST) Inorganic Crystal Structure Database (ICSD) 6287.
10.1103/PhysRev.98.337
10.1103/PhysRev.98.349
The concentration of paramagnetic species cannot be obtained from a Dysonian-type signal because of the shallow skin depth of microwaves. Thus the single crystal was crushed into fine powder with particle sizes smaller than the penetration depth of microwaves (∼1 μm diameter). CuSO 4 ·5H 2 O was used as a spin standard reference.

Dates

Type	When
Created	22 years, 1 month ago (July 31, 2003, 11:27 p.m.)
Deposited	1 year, 7 months ago (Jan. 9, 2024, 9:39 p.m.)
Indexed	2 days, 21 hours ago (Aug. 29, 2025, 6:01 a.m.)
Issued	22 years, 1 month ago (Aug. 1, 2003)
Published	22 years, 1 month ago (Aug. 1, 2003)
Published Print	22 years, 1 month ago (Aug. 1, 2003)

Funders 0

None

BibTeX

@article{Matsuishi_2003, title={High-Density Electron Anions in a Nanoporous Single Crystal: [Ca 24 Al 28 O 64 ] 4 + (4 e - )}, volume={301}, ISSN={1095-9203}, url={http://dx.doi.org/10.1126/science.1083842}, DOI={10.1126/science.1083842}, number={5633}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Matsuishi, Satoru and Toda, Yoshitake and Miyakawa, Masashi and Hayashi, Katsuro and Kamiya, Toshio and Hirano, Masahiro and Tanaka, Isao and Hosono, Hideo}, year={2003}, month=aug, pages={626–629} }

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  "abstract": "<jats:p>\n            We removed \u223c100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO\u00b77Al\n            <jats:sub>2</jats:sub>\n            O\n            <jats:sub>3</jats:sub>\n            , leading to the formation of high-density (\u223c2 \u00d7 10\n            <jats:sup>21</jats:sup>\n            cm\n            <jats:sup>\u2013</jats:sup>\n            <jats:sup>3</jats:sup>\n            ) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an\n            <jats:italic>F</jats:italic>\n            <jats:sup>+</jats:sup>\n            center and migrates throughout the crystal by hopping to a neighboring cage with conductivity \u223c100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca\n            <jats:sub>24</jats:sub>\n            Al\n            <jats:sub>28</jats:sub>\n            O\n            <jats:sub>64</jats:sub>\n            ]\n            <jats:sup>4</jats:sup>\n            <jats:sup>+</jats:sup>\n            (4\n            <jats:italic>e</jats:italic>\n            <jats:sup>\u2013</jats:sup>\n            ) may be regarded as a thermally and chemically stable single crystalline \u201celectride.\u201d\n          </jats:p>",
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