Volume 86, Number 3, May 2009
|Number of page(s)||4|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||22 May 2009|
Preparation and superconductivity of stoichiometric β-FeSe
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences - Shanghai 200050, PRC
2 Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences Shanghai 200050, PRC
Corresponding author: email@example.com
Accepted: 6 April 2009
The stoichiometric -FeSe superconductor was prepared for the first time by mechanical alloying (MA) from elemental powders of iron and selenium (1 : 1) and subsequent annealing process. The formation of the stoichiometric -FeSe is attributed to the MA resulting nanometric precursor containing high reaction activity for the following annealing process, and the MA mechanism here is a mechanic collision reaction (MCR). The crystalline phases in the MA precursor are tightly related to the milling time (t). Hexagonal γ-Fe7Se8, tetragonal -FeSe, and residual Fe coexist when t 5 h. A single -FeSe phase is observed when t = 10 h, and the crystalline size further decreases to ~ 10 nm. In the nanocrystalline state, hexagonal -FeSe is the stable and preferred phase. With the increase of the annealing temperature, -FeSe rapidly transforms to the well-crystallized -FeSe. At 400 °C, the pure stoichiometric -FeSe phase is successfully obtained with size of ~ 60 nm and the highest superconductor transition temperature of about 8.9 K in the -FeSe series.
PACS: 74.70.-b – Superconducting materials / 74.70.Ad – Metals; alloys and binary compounds (including A15, MgB2, etc.)
© EPLA, 2009
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