高温押し出し加工したBi系酸化物超伝導セラミックスの微細組織

概要

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Bi2Sr2CaCu2Ox ceramic powder prepared by a solid state reaction was encapsulated in Ag can with a dimensions of 32φ(O.D.)-20φ(I.D.)×55 ?? mm. The bullet (can containing ceramic powder) was preheated at 840°C for about 10 min and was extruded rapidly to avoid excessive heat loss. Many kinds of disordered structure were observed in the hot-extruded ceramics by TEM. They were mechanically disordered grain boundaries, microfractured grains, and amorphous regions. The disordered structure regions changed, however, to polycrystals composed of small grains without grain boundary second phase after annealing at 800°C for 1 hr. The densification mechanism of the Bi-superconducting ceramic powder during the hot-extrusion processing was discussed by considering the microstructural change.