Composition dependence of the critical temperature in superconducting Ga-1212 GaSr₂Tm_1−xCa_xCu₂O₇

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• 作者：Ono ; A. ; Tsutsumi ; M.
• 刊名：Physica C
• 出版年：1996
• 出版时间：November 10, 1996
• 年：1996
• 卷：271
• 期：3-4
• 页码：325-330
• 全文大小：562 K

文摘

GaSr₂Tm_1−xCa_xCu₂O₇ was prepared at 2 GPa. Energy dispersive X-ray (EDX) analysis reveals the formation of two kinds of Ga-1212 phases, GaSr₂(Tm,Sr,Ca)Cu₂O₇ and Ga(Sr,Ca)₂(Tm,Ca)Cu₂O₇, in the same sample. The formal Cu valence of the former phase is higher than that of the latter one. The superconducting transition temperature (T_c) increases with increasing formal Cu valence in the CuO₂ sheet. The optimum value of the formal Cu valence is above 2.23. The high critical value suggests the presence of a significant amount of localized holes not associated with superconductivity.