Awan, V. P. S. and Vajpayee, A. and Mudgel, M. and Ganesan, V. and Awasthi, A. M. and Bhalla, G. L. and Kishan, H. (2008) Physical property characterization of bulk MgB2 superconductor. European Physical Journal B, 62 (3). 281 -294 . ISSN 1434-6028

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Abstract

We report synthesis, structure/micro-structure, resistivity under magnetic field [rho(T)H], Raman spectra, thermoelectric power S(T), thermal conductivity kappa(T), and magnetization of ambient pressure argon annealed polycrystalline bulk samples of MgB2, processed under identical conditions. The compound crystallizes in hexagonal structure with space group P6/mmm. Transmission electron microscopy (TEM) reveals electron micrographs showing various types of defect features along with the presence of 3-4 nm thick amorphous layers forming the grain boundaries of otherwise crystalline MgB2. Raman spectra of the compound at room temperature exhibited characteristic phonon peak at 600 cm(-1). Superconductivity is observed at 37.2 K by magnetic susceptibility chi(T), resistivity rho(T), thermoelectric power S(T), and thermal conductivity kappa(T) measurements. The power law fitting of rho(T) give rise to Debye temperature (circle minus(D)) at 1400 K which is found consistent with the theoretical fitting of S(T), exhibiting circle minus(D) of 1410 K and carrier density of 3.81 x 10(28)/m(3). Thermal conductivity kappa(T) shows a jump at 38 K, i.e., at T-c, which was missing in some earlier reports. Critical current density (J(c)) of up to 10(5) A/cm(2) in 1-2 T (Tesla) fields at temperatures (T) of up to 10 K is seen from magnetization measurements. The irreversibility field, defined as the field related to merging of M(H) loops is found to be 78, 68 and 42 kOe at 4, 10 and 20 K respectively. The superconducting performance parameters viz. irreversibility field (H-irr) and critical current density J(c)(H) of the studied MgB2 are improved profoundly with addition of nano-SiC and nano-diamond. The physical property parameters measured for polycrystalline MgB2 are compared with earlier reports and a consolidated insight of various physical properties is presented.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/S Springer Verlag.
Subjects:	Physics
Divisions:	UNSPECIFIED
Depositing User:	Ms Neetu Chandra
Date Deposited:	27 Nov 2015 09:33
Last Modified:	27 Nov 2015 09:33
URI:	http://npl.csircentral.net/id/eprint/1648

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