کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1517324 | 1511586 | 2010 | 4 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Insulating state of Na clusters and their metallic transition in low-silica X zeolite
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی مواد
مواد الکترونیکی، نوری و مغناطیسی
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چکیده انگلیسی
Optical and magnetic properties are investigated for low-silica X (LSX) zeolite loaded with Na metals at various loading densities. In LSX, β-cages with the inside diameter of â¼7 Ã
are arrayed in a diamond structure and the supercages with that of â¼13Â Ã
are formed among them. When the average number of guest Na atoms per β cage, n, is smaller than â¼2, optical reflectance shows a peak at â¼2.5 eV. This corresponds to the 1s-1p transition of the cluster formed in β cage. At n>2, this peak disappears and several strong peaks are seen at 1-3 eV. The oscillator strength increases with n. They can be attributed to surface-plasmon-like excitations of the Na clusters formed in supercages. At nâ¤10, clear absorption tails with energy gaps are observed at near IR region indicating insulating states. However, when n is increased up to â¼12, a clear Drude reflection suddenly appears in the IR region, indicating that an insulator-to-metal transition abruptly occurs. This dramatic change of the electronic state may be caused by the successive connection between adjacent clusters in supercages due to some special arrangement of Na+ ions as well as the delocalized wave function of electrons at high Na-loading density.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Physics and Chemistry of Solids - Volume 71, Issue 4, April 2010, Pages 650-653
Journal: Journal of Physics and Chemistry of Solids - Volume 71, Issue 4, April 2010, Pages 650-653
نویسندگان
Takehito Nakano, Takahiro Mizukane, Yasuo Nozue,