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On the synthesis and characterization of La doped MgB2 superconductor
Authors:C Shekhar  R Giri  R S Tiwari  O N Srivastava
Abstract:We report the synthesis of La doped MgB2 superconductors with nominal compositions Mg1‐xLaxB2 (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 MgB2 samples. The bulk polycrystalline samples possess superconducting transition temperature Tc(R=0) ranging between 36‐39 K. It has been found that transport critical current density Jc of the samples change significantly with the doping level of La. A high transport (Jc) value ~1.9 x 103 A/cm2 at 15 K has been achieved for Mg0.97La0.03B2 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 MgB2 is done through sintering of Mg and B powders. The detailed microstructural investigations of Mg0.97La0.03B2 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 Mg0.97La0.03B2 superconductor has been attributed to the partial dislocations which are capable of providing pinning centres. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Keywords:superlattice structure  partial dislocation  moiré  fringe  transport critical current density
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