Effect of synthesis route on the structure of Nd3-xBa3+xCu6O14-2δ (x=0,1) system:: a neutron diffraction study

Structural studies on Nd3-xBa3+xCu6O14-2delta with 0less than or equal toxless than or equal to1 were carried out by Rietveld refinement procedure using neutron diffraction data. The composition x=1 was prepared both by the solid-state method and the nitrate-decomposition method. Quantitative multiphase analysis coupled with variation in the method of synthesis has shown conclusively that Nd did substitute for Ba even in a stoichiometric composition NdBa2Cu3O7-delta, irrespective of the method of synthesis. The fractional atomic substitution of Nd at the Ba site has been determined to be about 15%. The composition x=0, synthesised by the nitrate-decomposition method, has been found to be tetragonal with the space group P4/mmm. Nd has been found to substitute for Ba according to Nd(Ba0.75Nd0.25)(2)Cu3O7-delta and no random distribution of cations has been found along the c-direction. The observed tetragonality has been attributed to the additional oxygen taken into the basal (001) plane due to the substitution of trivalent Nd at the divalent Ba site. (C) 2002 Elsevier Science Ltd. All rights reserved.