Bi-Sr-Ca-Cu-O系のガラス形成能及び超伝導特性に対するGa添加効果

概要

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The effect of the addition of Ga_2O_3, a conditional glass former, on the glass-forming ability and superconducting properties of samples with Bi_<2-x>Ga_xSr_2Ca_2Cu_3O_y (x=0-1.5) compositions has been investigated. The quantity T_x-T_g increases from 54 to 68 K, indicating an improvement in the glass forming ability of the samples, where T_g and T_x are glass transition and crystallization temperatures, respectively. The superconducting properties deteriorate due to the migration of Ga ions into the 2212 phase: the superconducting critical temperature of the 2212 phase decreases from 85 K for Ga-free sample to 72 K for the sample with x=0.5, and the sample with x=1.5 shows semiconducting properties. The c-axis length of the 2212 phase decreases from 3.081 nm for Ga-free sample to 3.074 nm for the sample with x=0.5, but a- and b-axis lengths remain constant. A new Ga-compound formed in Ga-added samples was identified to be GaSr_<0.55>Ca_<1.05>Cu_<0.5>O_x. Superconducting phases of the Ga-based system are not formed even in Ga-rich samples.
社団法人日本セラミックス協会の論文
1997-03-01