Melting investigation of Bi2Sr1.9Ca2.1Cu3O10+x by high temperature X-ray diffraction and quenching

A combination of in-situ high temperature X-ray (HTXRD), quenching experiments and energy dispersive X-ray spectrometry (EDS) was used to investigate the melting sequence of the high T-c 2223 (Bi:Sr:Ca:Cu) superconductor phase. The occurrence and disappearance of various phases associated with the melting of this phase are discussed for both Ag-free and Ag-containing samples. In both Ag-free and Ag-containing samples, three insulator phases were observed during the melting process with HTXRD. In the Ag-free sample, melting started between 880 degrees C and 890 degrees C. At 890 degrees C, both (Sr,Ca)(14)Cu24O41 and (Ca,Sr)(2)CuO3 were present. The (Sr,Ca)(14)Cu24O41 phase disappeared at about 900 degrees C and (Ca,Sr)(2)CuO3 persisted until approximate to 950 degrees C, at which point (Ca,Sr)O was observed. In the Ag-containing sample, a similar melting sequence was observed except that the initial melting temperature of the 2223 phase was lowered by about 20-30 degrees C. Ag was found to enter the liquid. It appears that this liquid promotes grain growth and preferred orientation. It was found that the melting process of the 2223 phase is similar to that of the 2212 (Bi:Sr:Ca:Cu) phase in that both melt incongruently to strontium calcium cuprates. The quench experiments showed that the 119 x 5/22 x 1 phase was an additional primary phase during melting. The absence of this phase during the HTXRD experiment could be due to the fact that the 119 x 5/22 x 1 grains are denser than the liquid and therefore sink below the surface of the sample. (C) 1998 Published by Elsevier Science B.V. All rights reserved.