PROBLEMS IN THE LOW-TEMPERATURE SYNTHESIS OF 92-K SUPERCONDUCTING YBCO

YBCO with high granulometric perfection and low dispersion can be obtained by a low-temperature reaction (approximate to 800 degrees C) of atomic-scale dispersed powders, produced through the thermal decomposition of liquid precursors. As reacted such powders are tetragonal and not superconducting, but they transform into the high-T-c phase after optimized annealing treatments. We describe the method we developed and the characteristics of the materials we achieved, and we discuss the main features of the process in the light of the current know-how.