THERMAL EFFECTS ON THE MICROSTRUCTURE OF SUPERCONDUCTING (BI1.8PB0.35)SR2CA2CU3OY

Thermal effects on the microstructure of Bi2Sr2CaCu2Oy and (Bi, Pb)2Sr 2Ca2Cu3Oy superconductors are studied by electron diffraction and diff erential thermal analySiS (DTA). The DTA results show that there exist two endothermal peaks and one exothermal peak at about 530, 680 and 7 40-degrees-C respectively. The electron diffraction indicates that a 2 a, 2b, c superstructure is formed at about 450-degrees-C. The superstr ucture begins to disappear at about 650-degrees-C and the collapse of the crystal structure occurs at about 700-degrees-C, which is consiste nt with the results Of DTA. The superstructure originates in oxygen-va cancy ordering as for similar superstructures occurring in Bi2Sr2YCu2O y and YBa2Cu3O7-x.