Analysis of structural, electrical, and levitation properties of (RE: Nd, Sm, Gd) BCO-358 superconducting ceramics prepared by a modified MPMG technique

Abstract

RE3(Nd, Sm, Gd)Ba5Cu8Oy (RE358) superconducting ceramics were prepared by a modified Melt-Powder-Melt-Growth (MPMG) technique. The structural properties of samples were examined with bulk density, an X-Ray Diffractometer (XRD), a Polarized Optical Microscope (POM); their electrical properties were investigated with a four-point probe method; their levitation properties were measured with a closed-cycle cryostat levitation system. In the XRD measurement, minor phases such as RE211 were detected along with the superconductor phase. In the POM micrograph, it was observed that the Gd358 MPMG sample had fewer weak-link, bigger superconductor grains, smaller RE211 particles, and lower pore. The best T-c(onset), T-c(offset), and Delta T-c transition temperatures under applied magnetic field were found in the Gd358 MPMG sample from the electrical resistance measurement. The lowest beta value obtained from the activation energy was calculated as 0.23 for the Gd358 MPMG sample; that is, this value is quite well compared to the literature. It was concluded from the levitation measurement that the Gd358 MPMG sample had the maximum F-z,F-R value at all temperatures. A strong correlation was determined between temperature and alpha value estimated from F-z,F-R equation. It is hoped that the Gd358 sample would be used in superconducting devices from the point of view of technique and economics.