Multi-step process to prepare bulk BSCCO (2223) superconductor with improved transport properties

• Published in: Physica. C, Superconductivity Vol. 306; no. 1; pp. 21 - 33
• Main Authors: Tampieri, A., Calestani, G., Celotti, G., Masini, R., Lesca, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 10.09.1998; Elsevier Science
• Subjects: Applied sciences; BSCCO superconductor; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Chemistry; Electrotechnical and electronic ceramics; Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...); Exact sciences and technology; Inorganic chemistry and origins of life; Preparations and properties; Pyrolysis; Solid state; Sol–gel; Technical ceramics; Solid state; Pyrolysis; Sol–gel; BSCCO superconductor; Bismuth Oxides; Transition metal Compounds; Experimental study; Oxide ceramics; Alkaline earth metal Compounds; Powder; Multi-element compound; Copper Oxides; Hot pressing; Sol gel process; Sintering; Chemical preparation; Solid state reaction; Calcium Oxides; Manufacturing; Microstructure; Strontium Oxides; High temperature superconductor; Electroceramics
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(98)00353-0

BSCCO (2223) superconducting powders were prepared by three different techniques (solid state, pyrolysis and sol–gel) and with three different stoichiometries, especially based on variations of Ca/Sr ratio and Cu concentration. Pressureless sintering was performed on cold uniaxially pressed (1 GPa) samples, avoiding the drawbacks connected to hot-pressing; different hot-forging cycles were then applied to attain higher density and orientation factor. It was found that the process phenomenology is strictly linked to the powder starting stoichiometry: when composition is very near to the theoretical (2223), effects of secondary phase extrusion are observed during hot-forging, yielding a purification and inhibition of (2212) formation accompanied by an appreciable increase of J c respect to hot-pressed samples. When a Ca/Sr ratio is considerably >1, recrystallisation of (2223) from the liquid takes place, with a remarkable improvement of critical current density ( J c>10 4 A/cm 2). In this case the non-superconducting secondary phases act as intrinsic oxygen reservoir. Finally, when composition diverges even more from (2223) (Ca/Sr≫1 and Cu excess), the formation of too many precipitates of non-superconducting phases hinders the texturing process and more in general deteriorates the intergranular properties.