Since affirm that the MgB₂ is a potentially promising material for the large-scale application as superconducting devices, the proper doping substance that can increase the Jc or Tc has been intensively searched. One of the most interesting doping argent is nano-SiC powder.
We investigated the effect of the nano-powder SiC doping of two average grade batches: 6 nm and 18 nm, with the content up to 10 at. % for the commercial MgB₂ powder made by Alfa Aesar.
The syntheses have been made on the cylindrical samples of 3 mm in diameter and 5 to 7 mm in length. Such samples were obtained by uni-axial pressing at 1.5 GPa in three sectors open anvils.
Synthesis were made at an inert gas at pressure of up to 1 GPa at temperature from 1500 K to 1550 K, in the high pressure gas trap system, with the equilibrium magnesium vapor made by the melting of Mg chips inside close vessels, during the experiment lasting for two hours.
As obtained samples thus were superconducting with Tc over 39 K and the highest Tc at 42.6 K was recorded for the sample doped with 1.5 at % of the 6nm SiC. The XRD examinations indicated the MgB₂ phase and a very low addition of Mg, Si and C composites and/or SiC as well as Mg₂Si nano-crystallites. The compositions of the additional phase were strictly dependent of the nano-size grains dimensions (their solubility) and quantity. The lattice parameters for all samples were smaller than for pure MgB₂ initial samples. The SEM, EDX and superconducting properties Hc₂, Tc, Jc, were measured and discussed. The probably effect of tangential strain caused by nano-inclusion of thin amorphous or crystalline layer between the pure or carbon doped MgB₂ larger grain are considered for increasing the Tc of our samples.