PHASE-RELATIONS AND HOMOGENEITY REGION OF THE HIGH-TEMPERATURE SUPERCONDUCTING PHASE (BI,PB)(2)SR2CA2CU3O10+D

For the nominal composition of Bi2.27-xPbxSr2Ca2Cu3O10+d, the lead con tent was varied from x = 0.05 to 0.45. The compositions were examined between 800 and 890 degrees C which is supposed to be the temperatue r ange over which the so-called 2223 phase (Bi2Sr2Ca2Cu3O10+d) is stable . Only compositions between x = 0.18 to 0.36 could be synthezised in a single phase state. For x > 0.36, a lead-containing phase with a stoi chiometry of Pb-4(Sr,Ca)(5)CuOd with a small solubiliy of Bi is formed , for x < 0.18 mainly Bi2Sr2CaCu2O8+d and cuprates are the equilibrium phases. The temperature range for the 2223 phase was found to be 800 to 890 degrees C but the 2223 phase has extremely varying cation ratio s over this temperaure range. Former single phase 2223 samples turn to multiphase samples when annealed at slightly higher or lower temperau res. A decrease in the Pb solubility with increasing as well as decrea sing temperature with a maximum at about 850 degrees C was found for t he 2223 phase.