EFFECT OF LEAD LOSS AND SHEATH STRUCTURE ON PHASE-FORMATION AND ALIGNMENT IN (BI,PB)(2)SR2CA2CU3O10+DELTA AG COMPOSITE CONDUCTORS/

The effects of metallic constituent evaporation and sheath structure o n grain growth and alignment in silver-sheathed (Bi,Pb)(2)Sr2Ca2Cu3O10 +delta (Bi-2223)/Ag composites have been investigated by inductively c oupled plasma/atomic emission spectroscopy (ICP/AES), X-ray diffractio n, scanning electron microscopy, and energy dispersive X-ray spectrosc opy, Specimens of Bi-2223/Ag composites fabricated by the oxide-powder -in-tube technique mere peeled (opened) lengthwise to expose the ceram ic powder core, and then heat-treated in 0.075 atm of oxygen for selec ted temperatures and times, The results were compared with those for a s-processed samples with closed silver sheaths treated under identical conditions, ICP/AES analysis indicated that lead was the only metalli c element to undergo substantial evaporation during annealing of opene d samples, The lead-release process in parallel with the Bi-2223 forma tion reaction had an activation energy of similar to 25 kJ/mol, Lead l oss from the opened samples resulted in incomplete conversion to Bi-22 23, The combined results show that the silver sheath effectively preve nts evaporative lead loss, preserves and promotes densification, and i nduces texturing of the layered phases.