Effects of carbon additions to melt-processed YBa/sub 2/Cu/sub 3/O/sub x/ and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ compacts

YBa/sub 2/Cu/sub 3/O/sub x/ (Y-123) and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ (Bi-2212) compacts were partial-melt processed. Carbon was introduced into the compacts either by vibratory milling in an organic solution or by heat treating in an atmosphere containing a controlled concentration of CO/sub 2/. The presence of carbon had a strong effect on the melting response of Y-123, but not Bi-2212. For both materials, magnetic-hysteresis width was strongly expanded with added carbon. Transmission electron microscopy revealed nanometer-scale precipitates in specimens exposed to excess carbon. These precipitates are thought to be responsible for enhanced flux pinning.