THE EFFECT OF OXYGEN NONSTOICHIOMETRY ON THE PROPERTIES AND STRUCTURE OF THE LOW TC PHASE IN BI-SR-CA-CU-O SUPERCONDUCTOR

The properties and structure of the low Tc phase in Bi-Sr-Ca-Cu-O superconductors was greatly affected by the oxygen content, which was varied by annealing specimens in various atmospheres. The Tc of low Tc phase increased up to 100 K by annealing in nitrogen. Annealing in nitrogen caused the reversible weight loss of about 0.2% and the increase in the c-axis by 0.01 nm. The variation of microstructure was examined by TEM. The average period of modulation in Bi-O layer was found to be unvaried (2.7nm) but the detailed local structure seemed to be disordered by oxygen evolution.