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
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد مواد الکترونیکی، نوری و مغناطیسی
پیش نمایش صفحه اول مقاله
Insulating state of Na clusters and their metallic transition in low-silica X zeolite
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 ∼7 Å are arrayed in a diamond structure and the supercages with that of ∼13 Å are formed among them. When the average number of guest Na atoms per β cage, n, is smaller than ∼2, optical reflectance shows a peak at ∼2.5 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 n≤10, clear absorption tails with energy gaps are observed at near IR region indicating insulating states. However, when n is increased up to ∼12, 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
نویسندگان
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