Fabrication of bulk Y-Ba-Cu-O superconductors with artificial holes through oxidation of carbon rods

We fabricated bulk Y-Ba-Cu-O superconductors with artificial holes that were created by oxidizing carbon rods embedded in the precursor pellets. Twenty carbon rods 500 μm in diameter and 5 mm in length were compacted with bulk Y-Ba-Cu-O precursor pellets such that carbon rods were parallel to the thickness direction. Then the precursors were heated at 1000 °C and 1050 °C. During the heating process, carbon rods reacted with ambient oxygen and twenty holes were successfully produced. With oxygen annealing treatment, the bulk Y-Ba-Cu-O superconductors with 20 holes exhibited superconductivity. Microstructural observations showed that the grain size around carbon rods was larger than that of the interior region. This was probably due to the fact that the temperature near the carbon rod was raised since the reaction of carbon and oxygen is exothermic. We also noticed that the formation of pores was largely inhibited near the holes.