Synthesis of superconductor oxide ceramics by combustion of carbon nanoparticles

We report a novel cost-effective and simple method to produce superconductor YBa2Cu3O7-delta (YBCO) powder by a self-sustaining one step process, named Carbon Combustion Synthesis of Oxides (CCSO). In this process the exothermic oxidation of carbon nanoparticles generates a thermal reaction wave that propagates at a velocity of about 1 mm/s through the solid reactant Y2O3, BaO2, CuO mixture, converting it rapidly (order of seconds) to YBCO. The carbon is not incorporated in the product and is emitted as CO2 from the sample generating a highly porous (similar to 70%) and friable product. Most of the grains have a plate-like shape, are well connected and have a size distribution ranging from 1 to 3 mu m. Carbon analysis indicated that the concentration of the residual carbon was less than 0.06 wt %. The magnetization of as-synthesized samples, determined by SQUID magnetometer showed an onset of superconducting (SC) transition at similar to 91 K, with a 44% shielding fraction of the -1/(4 pi) value.