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On the synthesis and characterization of La doped MgB 2 superconductor
Author(s) -
Shekhar C.,
Giri R.,
Tiwari R. S.,
Srivastava O. N.
Publication year - 2004
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200310244
Subject(s) - superconductivity , materials science , crystallite , doping , transmission electron microscopy , analytical chemistry (journal) , critical current , electrical resistivity and conductivity , crystallography , nanotechnology , condensed matter physics , chemistry , metallurgy , optoelectronics , physics , quantum mechanics , chromatography
We report the synthesis of La doped MgB 2 superconductors with nominal compositions Mg 1‐x La x B 2 (with x = 0.01, 0.03, 0.05, 0.07) by solid state reaction at ambient pressure. A special encapsulation technique has been used by us to prepare high quality superconducting MgB 2 samples. The bulk polycrystalline samples possess superconducting transition temperature T c(R=0) ranging between 36‐39 K. It has been found that transport critical current density J c of the samples change significantly with the doping level of La. A high transport (J c ) value ∼1.9 x 10 3 A/cm 2 at 15 K has been achieved for Mg 0.97 La 0.03 B 2 sample. The XRD and TEM investigations indicate that the samples prepared by encapsulation method are devoid of MgO, which is generally found when synthesis of MgB 2 is done through sintering of Mg and B powders. The detailed microstructural investigations of Mg 0.97 La 0.03 B 2 specimens by transmission electron microscopy (TEM) reveal the presence of partial dislocation network, moiré fringes and superlattice structure in the as synthesized samples. The higher transport critical current density observed in Mg 0.97 La 0.03 B 2 superconductor has been attributed to the partial dislocations which are capable of providing pinning centres. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)