# Structure and properties of oxyanion derivatives of 123 cuprate superconductors: effect of substitution of carbonate and nitrate ions in the Cu(1) position of $(YBaSrCu_3O_{7-\delta})$

Rao, CNR and Nagarajan, R and Mahesh, R and Kulkarni, GV and Ayyappan, S and Subbanna, GN (1993) Structure and properties of oxyanion derivatives of 123 cuprate superconductors: effect of substitution of carbonate and nitrate ions in the Cu(1) position of $(YBaSrCu_3O_{7-\delta})$. In: Solid State Communications, 88 (10). pp. 757-760.

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## Abstract

When the Cu(1) site In orthorhombic $YBaSrCu_30_{7-\delta}$ $(T_c$ = 80 K), is partly substituted by the carbonate Ion (upto 50%), the crystal structure becomes tetragonal and the electron diffraction pattern shows evidence for 2a x 2c superstructure; the material however is not superconducting. The same is true when Y is partly replaced by Ca as in $YCaBa_2Sr_2Cu_5(CO_3)0_y$. When the $CO_3$ group is partly replaced by $NO_3$ group as in the $YCaBa_2Sr_2Cu_5(CO_3)_{1-x}(No_3)_xO_y$, the structure, remains the same but superconductivity is retained. IR spectroscopic studies show that both $CO_3$ and $NO_3$ coordinate strongly and are not present as free ions in these oxyanion cuprate derivatives. Cu K-EXAFS studies on the carbonate and carbonato-nitrate derivatives confirm the presence of the oxyanions in the place of $CuO_4$ units in the Cu-O chains.

Item Type: Journal Article Copyright of this article belongs to Elsevier Science. Division of Chemical Sciences > Materials Research CentreDivision of Chemical Sciences > Solid State & Structural Chemistry Unit 03 Jul 2008 19 Sep 2010 04:46 http://eprints.iisc.ernet.in/id/eprint/14575