발간논문

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Vol.29, No.7, 695 ~ 703, 1991
Title
Fabrication of Metallic Precursor for High Tc Superconductor by Vacuum Arc Melting Process
이규환Kyu Hwan Lee, 신명철Myung Chul Shin
Abstract
Bi-Pb-Sr-Ca-Cu metallic precursor for high Tc superconductor was manufactured in a vaccuum arc melting furnace and the oxidation mechanism of this precursor was studied by differential scanning calorimetry and X-ray diffractometry. The optimal melting process was to melt the whole alloying elements except Sr in one charge. The master alloys such as Cu-Ca, Bi-Sr-Pb, Cu-Sr, and Pb-Bi do not give the sound melting stock retaining volatile Sr and Ca. The melting of Cu-Bi-Ca-Pb in one charge and then the alloying of this melting stock with Sr gives a sound ingot. The separation of liquid phases during melting was reduced in extent by the addition of Pb in the Bi-Sr-Ca-Cu system. The mechanism for the oxidation of the precursor was revealed as follows. 1. Formation of SrPbO₃ from the matrix in the low temperature range. 2. Formation of the low Tc 2212 phase in the SrPbO₃ with diffusion of Bi and Ca from the matrix and Cu from the separated phase. 3. Formation of high Tc 2223 phase in the 2212 phase with further diffusion of Ca and Cu from the separated phase.
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