The effect of C and (Er, Sm, Eu)2O3 doping and high isostatic pressing on superconducting properties of MgB2 phase and volume of cylindrical MgB2 ceramic samples

Abstract

We present our research on the influence of pressure on the synthesis of the MgB2 phase and, consequently, on the superconducting properties of the MgB2 system. We investigated undoped, C-doped, and double-doped, i.e. C and Re2O3 Re = Sm, Eu, Er), MgB2 samples. We conducted comparative studies of critical temperature, irreversibility field, critical current and pinning force for ceramic samples annealed at ambient pressure and 1 GPa. Heat treatment under high isostatic pressing (HIP) of 1 GPa reduced the volume of the undoped MgB2 cylinder by 40%. This significantly increases the density, homogeneity and number of connections between the grains, and also eliminates voids in the undoped material. However, we did not observe any reduction in the volume of C-doped and double-doped MgB2 cylinders. Our research shows that the critical parameters of the MgB2 superconductor can be increased more effectively by doping C and the HIP process than by double doping C with Er, Sm or Eu and the HIP process. The HIP process improved the efficiency of pinning centers created by magnetic admixtures with a low magnetic moment (Sm and Eu), but on the other hand, reduced this efficiency for admixture with a high magnetic moment (Er).