MELTING INVESTIGATION OF BI2SR1.9CA2.1CU3O10-TEMPERATURE X-RAY-DIFFRACTION AND QUENCHING(X BY HIGH)

A combination of in-situ high temperature X-ray (HTXRD), quenching exp eriments and energy dispersive X-ray spectrometry (EDS) was used to in vestigate the melting sequence of the high T-c 2223 (Bi:Sr:Ca:Cu) supe rconductor phase. The occurrence and disappearance of various phases a ssociated with the melting of this phase are discussed for both Ag-fre e 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 a nd 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 abo ut 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 initi al melting temperature of the 2223 phase was lowered by about 20-30 de grees C. Ag was found to enter the liquid. It appears that this liquid promotes grain growth and preferred orientation. It was found that th e 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 ph ase 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.