C6H6掺杂MgB2超导块材的制备及其磁通钉扎机制

Preparation and Flux Pinning Mechanism of C6H6-doped MgB2 Superconductor Bulk

以镁粉(Mg)、硼粉(B)和苯(C6H6)为原料,经高能球磨和固相烧结制备C6H6掺杂的MgB2超导块材,研究C6H6掺杂对MgB2相演化、微观结构及超导临界电流密度Jc的影响。结果表明:C6H6掺杂几乎不改变MgB2的形成温度;C进入MgB2晶格替代B,晶格常数a逐渐减小,晶粒逐渐细化;掺杂C6H6摩尔分数为0.04的MgB2样品具有相对低的超导临界转变温度Tc,为31 K,但却表现出优异的Jc,其在高温20 K、高磁场强度2 T下,Jc保持在3.6×10^4 A/cm^2,这主要得益于晶界钉扎和点钉扎的混合磁通钉扎机制。

C6H6-doped MgB2 superconductor bulks were synthesized by ball milling subsequently solid state sintering using magnesium powder(Mg),boron powder(B)and benzene(C6H6)as raw materials.The effects of C6H6 doping on phase evolution,microstructure and the critical current density Jc of MgB2 were investigated.The results show that C6H6 doping has little effect on the formation temperature of MgB2.C enters the lattice of MgB2 by substitution for B,which makes the decreasing of lattice constant a and the grain size refines gradually.C6H6-doped MgB2 sample with molar fraction of 0.04 has relatively low superconducting transition critical temperature Tc of 31 K,but exhibits the excellent Jc.At high temperature 20 K and high magnetic density 2 T,Jc remains at 3.6×10^4 A/cm^2,which is mainly due to hybrid flux pinning mechanism of grain boundary pinning and point pinning.