New quadruple perovskites Ln2Ba2TixSn2–xCu2O11, (0⩽x⩽2): controlling copper–oxygen distances in potential superconducting parent phases
- 1 January 1993
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry
- Vol. 3 (9) , 979-982
- https://doi.org/10.1039/jm9930300979
Abstract
The compounds Nd2Ba2Cu2SnTiO11, Sm2Ba2Cu2Sn0.5Ti1.5O11 and Gd2Ba2Cu2Ti2O11 have been synthesized by reaction of the component oxides at 1025 °C and their structures refined from powder X-ray diffraction data. The materials crystallise with a quadrupled perovskite unit cell, similar to that of La2Ba2Cu2Sn2O11 containing alternating double layers of copper and titanium/tin. Decreasing lanthanide size and increasing titanium content is associated with a marked unit cell contraction and a reduction in the mismatch between the different double-layer dimensions. A reduction in the copper–oxygen distances in the CuO2 planes from 2.007 Å in La2Ba2Cu2Sn2O11 to 1.951 Å in Gd2Ba2Cu2Ti2O11 produces a copper–oxygen interaction similar to that found in high-temperature superconductors.Keywords
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