Abstract
The electron doped Ln2−xCexCuO4 (Ln=lanthanide) oxides have intergrowth structures consisting of superconductively active CuO2 sheets alternating with inactive (Ln, Ce)2O2 fluorite layers along the c-axis. Stabilization of such intergrowth structures requires bond length matching across the intergrowth interface. The bond length matching criterion causes a monotonic decrease in the Ce solubility limit from x=0.24 to x=0.15 as the size of Ln3+ decreased from Ln=La0.5Nd0.5 to Ln=Gd. Annealing in N2 atm of Ln2−xCexCuO4 at temperatures above 900°C creates oxygen vacancies and the number of vacancies decreases with increasing Ce content. The value of x at which a semiconductor to superconductor transition occurs in Ln2−xCexCuO4 increases with decreasing size of Ln3+ due to an increasing Madelung energy caused by a decreasing Cu−O bond length.
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Manthiram, A., Zhu, Y.T. Chemistry of electron doped Ln2−xCexCuO4 superconductors. J. Electron. Mater. 22, 1195–1198 (1993). https://doi.org/10.1007/BF02818060
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DOI: https://doi.org/10.1007/BF02818060