Influence of CaCuO2 Particle Size on Phase Evolution of Bi-based High Temperature Superconductors Prepared by Two-powders Route

Bi1.76Pb0.34Sr1.93Ca2.0Cu3.06O8+delta (Bi-2223) precursor powders were fabricated with a two-powder route based on co-precipitation process. During this process, Bi1.76Pb0.34Sr1.93Ca2.0Cu3.06O8+delta (Bi-2212) and CaCuO2 (with the actual phase composition of Ca2CuO3 and CuO) powders were first synthesized and calcined separately, and then mixed together before packed into Ag sheath. By adjusting the pH values during the co-precipitation process, CaCuO2 powders with different average particle sizes of about 1.10, 0.75, and 0.60 p.m were obtained. Then single filament Bi-2223/Ag tapes were fabricated by powder in tube (PIT) process with precursor powders obtained by mixing the different particle sized CaCuO2 powders and well-calcinated Bi-2212 powders. The influences of CaCuO2 particle size on microstructure, phase evolution dynamics and superconducting current capacity of sintered Bi-2223 tapes were studied. Results show that due to higher uniformity of Ca2CuO3 and CuO distribution in filaments, clustering of secondary phases and insufficiently reacted areas are effectively avoided. Therefore, higher current density of similar to 12 200 A.cm(-2) is obtained for the 1# tape by further optimizing the final dimension of the tapes.