Effects of grain boundaries on electrical and magnetic properties of melt-processed SmBa2Cu3Ox superconductors

In the present study, we examine the energy dissipation mechanisms and grain boundary effects on the superconducting properties of high-Tc SmBa2Cu3O7−x samples. Sm-123 was synthesized with the top-seeded-melt-growth technique. Grain sizes, as determined by optical microscopy, ranged between 0.5 mm and 1.5 mm. Thus, each specimen, on which the electrical and magnetic measurements were carried out, contained several grains. Some of our findings are as follows: (1) the intragrain Tc is 93.5 K and the intergrain Tc is 87.5 K. Superconducting transition width is narrow and is not affected much by the magnetic field. (2) The intragrain Jc is 110,000 A cm−2 while the intergrain Jc is 210 A cm−2 at 10 K. (3) The intergrain Jc shows a secondary peak with the increase in temperature from 10 K to 30 K. The main reasons behind these observations are discussed in detail.