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 particle size on the reaction paths leading to binary phases in the Y-Ba-Cu-O system. Using dynamic X-ray diffraction (DXRD), three binary reaction sets with stoichiometries equal to that present in the Y-Ba-Cu high-Tc superconductor and having two different particle sizes (nanometers 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 and Ba-Cu binaries. Particle size comparisons show not only a higher reactivity in the nanometer system, but also different products due to the 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