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Analysis of YBa 2 Cu 3 O 7-δ Peritectic Reactions and Orientation by High Temperature XRD and Optical Microscopy

1991; International Centre for Diffraction Data; Volume: 35; Issue: A Linguagem: Inglês

10.1154/s0376030800009344

2631-3626

Robert L. Snyder, Mark A. Rodriguez, B. J. Chen, D. P. Matheis, H. Göbel, G. Zorn, B. Seebacher,

Advanced Chemical Physics Studies

Abstract Real time observations of the YBa 2 Cu 3 O 7-δ (123) melting process by high temperature XRD and optical microscopy reveal a reaction sequence which does not correspond well with the literature. CO 2 gas, present in the air, reacts with 123 to produce the Y 2 CU 2 O 5 phase. This reaction begins well below 800°C and persists up to 970°C when BaCuO 2 begins to form. The previously unreported BaCuO 2 reaction occurs in either air or oxygen and this phase grows at the expense of the 123 until both rapidly disappear at 1050°C with the appearance of Y 2 B 2 CuO 5 (211), Formation of Y 2 O 3 from the 211 melt occurs more slowly, beginning at 1150°C. Dynamic 00ℓ orientation has been observed at 950°C upon cooling from the melt. The orientationa) growth is believed to be a surface tension dependent, liquid assisted sintering reaction.