YBa_2Cu_3O_xセラミックスにおける超伝導特性に及ぼす粒界構造の影響

概要

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The critical current density (J_c) in small-grained YBa_2Cu_3O_x ceramics with varied sintered densities has been found to show characteristic behavior with a peak around a relative sintered density (R.D.) of 90%. This characteristic behavior of J_c in the materials has been investigated from the view points of the changes of both their grain morphologies and grain boundary dislocation structures (GBD) associated with sintered density. GBD networks occurred to relax the localized strain at the grain boundaries regardless the degree of lattice matching thereof, which was estimated using a coincidence-site-lattice (CSL) model. The GBD networks existing at the boundaries were found to reduce the J_c of the materials. The width (δ) of GBD in the materials, determined by transmission electron microscopy, was found to increase rapidly above 90% R.D. The increase in δ isexplained in terms of accumulated internal stresses at the grain boundaries, which are assumed to originate from an increase in the aspect ratio of the ceramic grains.
社団法人日本セラミックス協会の論文
1995-05-01