Contribution of simultaneous SiC and TaB2 additions on the MgB2 superconducting properties

L.B. SARNO DA SILVA; G. SERRANO; A. SERQUIS; M. T. MALACHEVSKY; D. RODRIGUEZ JR.

Rio de Janeiro

Conferencia; 11th International Conference on Applied Materials ICAM 2009; 2009

The use of MgB2 in superconducting applications that uses large magnetic fields depends on the development of a material where current-carrying performance (i.e. the critical current density Jc) and critical magnetic field (Hc2) are optimized simultaneously [1]. The best results for increasing Jc and the irreversibility field (Hirr) in bulk samples are related to an improvement in grain connectivity [2] but also to the addition of suitable defect nanoparticles or doping, i.e. Mg(B1−xOx)2 [3], SiC [4-6], Al [7], Dy2O3 [8], and carbon nanotubes (CNT) [9–12]. Many groups around the world work to improve the current transport properties of MgB2 at high fields (above 10T) aiming its use in magnets for particle accelerators and systems for nuclear fusion tests. On the contrary, modern magnetic resonance imaging systems work in the range 0.5 to 2.0T. In the present work it is described the production of MgB2 samples by using the mixture of the MgB2 with different additions: other diborides like TaB2 and ZrB2, which have the same C32 hexagonal structure as the MgB2, and SiC, that may contribute with C, to replace B in the crystalline structure of the matrix. The mechanical mixture of the powders, obtained by ball milling, has a positive influence in the final crystalline structure, maintaining the hexagonal structure, and generating intragranular and intergranular pinning centers. Microstructural characterizations through SEM and XRD, were used to determine the distribution and composition of the superconducting phase with the different additions. Magnetization Jc wás used to determine the best composition of the mixture and heat treatment profile. It is interesting to combine the different defects to enhance not only the high-field current carrying performance but also the low-field one. As a result, Jc was improved in low magnetic field when just TaB2 is used as dopant. However, when SiC is added together with TaB2, the result is the improvement of Jc in high fields.