Singh, K. P. and Awana, V. P. S. and Shahabuddin, Md. and Husain, M. and Saxena, R. B. and Nigam, Rashmi and Ansari, M. A. and Gupta, Anurag and Narayan, Himanshu and Halder, S. K. and Kishan, H. (2006) Phase formation and superconductivity of Fe-TUBE encapsulated and vacuum-annealed MgB2. Modern Physics Letters B, 20 (27). pp. 1763-1769. ISSN 0217-9849

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Abstract

We report optimization of the synthesis parameters viz. heating temperature (T-H), and hold time (t(hold)) for vacuum-annealed (10(-5) Torr) and LN2 (liquid nitrogen) quenched MgB2 compound. These are single-phase compounds crystallizing in the hexagonal structure (space group P-6/mmm) at room temperature. Our XRD results indicated that for phase-pure MgB2, the T-H for 10(-5) Torr annealed and LN2-quenched samples is 750 degrees C. The right stoichiometry i.e., MgB2 of the compound corresponding to 10(-5) Torr and T-H of 750 degrees C is found for the hold time (t(hold)) of 2.30 hours. With varying t(hold) from 1-4 hours at fixed TH (750'C) and vacuum (10(-5) Torr), the c-lattice parameter decreases first and later increases with t(hold) (hours) before a near saturation, while the a-lattice parameter first increases and later decreases beyond a t(hold) of 2.30 hours. The c/a ratio versus t(hold) plot showed an inverted bell-shaped curve, touching the lowest value of 1.141, which is the reported value for perfect stoichiometry of MgB2. The optimized stoichimetric MgB2 compound exhibited superconductivity at 39.2 K with a transition width of 0.6 K. In conclusion, the synthesis parameters for phase pure stoichimetric vacuum-annealed MgB2 compound are optimized and are compared with widely-reported Ta tube encapsulated samples.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s World Scientific Publishing.
Subjects:	Applied Physics/Condensed Matter Physics > Mathematical Physics
Divisions:	UNSPECIFIED
Depositing User:	Users 27 not found.
Date Deposited:	09 Aug 2018 08:34
Last Modified:	09 Aug 2018 08:34
URI:	http://npl.csircentral.net/id/eprint/2587

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