Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Hot Isostatic Pressure Process, Microstructure and Critical Parameters of MgB₂ and FeSe Superconductors Material

G. Gajda, A. Morawski, E. Nazarova, N. Balchev, K. Buchkov, T. Cetner

International Laboratory of High Magnetic Fields and Low Temperatures,Wroclaw, Poland

The annealing at high isostatic pressure (HIP – hot isostatic pressure) is very advantageous because it allows increase the uniformity and density of the superconducting material and increases the melting point of Mg. Higher density and better uniformity allows to obtain more connections between the grains. The higher melting temperature allows for smaller grains. Small grains also lead to more connectivity, between the grains. Moreover, HIP process increases the density of pinning centers, irreversible magnetic field (B_irr) and upper magnetic field (B_c2). The greater number of connections between the grains and the more pinning centers increases the critical current density.

We show results (MgB₂ bulks) of the magnetic critical current density at 4.2 K and 20 K (J_cm), critical temperature (T_c), irreversible magnetic field (B_irr), and photo with scanning electron microscope (SEM). Magnetic critical current was calculated with Bean model. The bulks were manufactured by Institute of High Pressure Physics PAS., with the precursor Mg+B powder. The Hot Isostatic Pressing (HIP) process has been performed at IHPP PAS Unipress with high Ar gas pressure for bulks samples of about 5 mm length. The 0.1 MPa to 1 GPa argon gas pressure was used in the HIP annealing, at temperature of 800 °C by 1h.

Moreover, we present transport results for FeSe bulks e g. critical temperature (T_c), irreversible magnetic field (B_irr), upper magnetic field (B_c2) and photo with scanning electron microscope (SEM). These bulks were manufactured by Institute of Solid State Physics BAS in Sofia. The Hot Isostatic Pressing (HIP) process has been performed at IHPP PAS Unipress with high Ar gas pressure of 1 GPa at 700 ^oC by 1h.