Spectroscopic behaviour of some superconducting materials containing tetraoxoanions

A number of materials of composition YSr₂Cu₂.(XO₄)₀.₂Oy(X = S, P, V) and others in which Y (III) was partially replaced by Sr(II) and/or Ca(II) were prepared by solid state reactions. Their unit cell parameters were determined and refined from X-ray powder data. The infrared spectra of the different tetraoxoanions incorporated in these materials were analyzed and discussed in detail. The vibrational modes of the other structural units present in these lattices were also approximately assigned in comparison with known spectral data of related materials.Centro de Química Inorgánic

The vibrational spectrum of Nd<SUB>2</SUB>BaCuO<SUB>5</SUB>

Compounds of general composition Ln2BaCuO5 (Ln=lanthanide) adopt different structural types. Two series of structures have been reported for LnzBaCuO5 compounds. For lanthanide ions smaller than Nd(III) (Y and Sm-Lu) the so-called "green phases" (orthorhombic, space group Pbnm) are stabilized. They are one of the main impurities generated during the synthesis of the LnBa2Cu3OT_x-type high-T¢ superconducting oxides. A different structural type (tetragonal, space group P4/mbm) becomes stabilized for Ln = La or Nd, although in the case of the lanthanum-containing material the totally stoichiometric composition does not seem to be attainable.Facultad de Ciencias Exacta