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Phase evolution of MgB2 prepared under high pressure

Published online by Cambridge University Press:  29 February 2012

Yaxin Sun  and
Dongli Yu
Yaxin Sun
Affiliation:
State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, China and School of Materials Science and Engineering, Anhui University of Technology, Ma’anshan 243000, China
Dongli Yu
Affiliation:
State Key Laboratory of Metastable Materials Science and Technology and College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, China
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Abstract

MgB2 superconductors were synthesized at high pressure and high temperature (HPHT) using pure Mg and B as raw materials. The effects of the experimental conditions such as pressure and temperature on phase evolution were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), and DC magnetization techniques. Results showed that high pressure and high temperature are two important factors for synthesizing the MgB2 phase. Stable MgB2 can be most effectively obtained in a pressure-temperature region from 3 to 6 GPa and between the melting points of Mg up to 1100 to 1300 °C. MgB2 starts to decompose into MgB4 at higher temperatures and pressures. The decomposition temperature of MgB2 increases with increasing pressure. The superconducting transition temperature Tc(bulk) was measured to be 38.0 to 38.8 K for MgB2 prepared at 900 to 1000 °C under 3 GPa. The larger grains and better crystalline perfection contribute to the higher Tc(bulk) and the narrower ΔT.

Keywords

MgB2high pressurehigh temperaturephase evolution

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Type
Technical Articles
Information
Powder Diffraction , Volume 23 , Issue 4 , December 2008 , pp. 334 - 337
Copyright
Copyright © Cambridge University Press 2008

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