Progress in Superconductivity

The Korean Superconductivity Society (한국초전도학회)
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Effects of Polyacrylic Acid Doping on Microstructure and Critical Current Density of $MgB_2$ Bulk

$MgB_2$ bulk의 미세구조와 임계전류밀도에 미치는 polyacrylic acid doping 효과

  • Lee, S.M. (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Hwang, S.M. (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Lee, C.M. (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Joo, J. (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Kim, C.J. (Neutron Science Division, Korea Atomic Energy Research Institute)
  • Received : 2010.03.05
  • Accepted : 2010.04.16
  • Published : 2010.04.30
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Abstract

We fabricated the polyacrylic acid (PAA)-doped $MgB_2$ bulks and characterized their lattice parameters, actual C substitutions, microstructures, and critical properties. The boron (B) powder was mixed with PAA using N,N-dimethylformamide as solvent and then the solution was dried out at $200^{\circ}C$ and crushed. The C treated B powder and magnesium powder were mixed and compacted by uniaxial pressing at 500 MPa, followed by sintering at $900^{\circ}C$ for 1 h in high purity Ar atmosphere. We observed that the PAA doping increased the MgO amount but decreased the grain size, a-axis lattice constant, and critical temperature ($T_c$), which is indicative of the C substitution for B sites in $MgB_2$. In addition, the critical current density ($J_c$) at high magnetic field was significantly improved with increasing PAA addition: at 5 K and 6.6 T, the $J_c$ of 7 wt% PAA-doped sample was $6.39\;{\times}\;10^3\;A/cm^2$ which was approximately 6-fold higher than that of the pure sample ($1.04\;{\times}\;10^3\;A/cm^2$). This improvement was probably due to the C substitution and the refinement of grain size by PAA doping, suggesting that PAA is an effective dopant in improving $J_c$(B) performance of $MgB_2$.

Keywords

References

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