The effect of residual carbon on the superconducting properties of YBa2Cu3O7−x powders

Abstract

Dependence of the contents and the states of residual carbon in YBa2Cu3O7−x powders synthesized by the sol-gel method on heating conditions, and effects of residual carbon on the superconducting properties were investigated. The carbon content of the powder heated at 950 °C for 20 h was reduced to 0.02%. It has been found that a large number of carbonaceous materials in the starting materials that are used in the sol-gel method does not affect the carbon content of synthesized superconducting powders. The volume of diamagnetism was increased and the Tc,onset was raised as the carbon contents were reduced to 0.04%. These properties were further improved by O2–HIP treatment at 500 °C.