EFFECT OF PARTICLE-SIZE ON BINARY REACTIONS COMMON TO THE Y-BA-CU-O SYSTEM

A systematic study has been conducted to determine the effects of part icle size on the reaction paths leading to binary phases in the Y-Ba-C u-O system. Using dynamic X-ray diffraction (DXRD), three binary react ion sets with stoichiometries equal to that present in the Y-Ba-Cu hig h-T(c) superconductor and having two different particle sizes (nanomet ers and micrometers) were reacted in both air and helium environments. Results indicate that the absence of oxygen and carbon dioxide leads to lower reaction temperatures and to different products in the Y-Cu a nd Ba-Cu binaries. Particle size comparisons show not only a higher re activity in the nanometer system, but also different products due to t he diffusion limitations in the micrometer system. Comparisons between the binary and ternary reactivities point to the Ba-Cu binary as the most critical reaction system for assuring high-quality HTSC.