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

Abstract

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.