Relation between Microstructure and Tc of Ba2-xEu1+xCu3O7-y Compounds

Abstract

Relation between Tc and Cu-Cu,Cu-O bond length for Ba2−xEu1+x Cu3O7−y compounds as a function of x (O<x<0.5) and y (0.1<y<0.7) values was investigated. Tc of these compounds decreased with increasing x and y values. The Cu(l)-Cu(2) bond length of Ba2−xEu1+xCu3O7−δ was almost constant for 0 < x < 0.5. The Cu(l)-O(3) and Cu(2)-O(3) bond length was also constant for 0 < x < 0.25, on the other hand, Cu(l)-O(3) bond length decreased and Cu(2)-O(3) bond length increased for 0.3 < x, respectively. The Cu(l)-Cu(2) and Cu(2)-O(3) bond length of Ba2EuCu3O7−y increased for 0<y<0.7, however, Cu(1)-0(3) bond length was almost constant in these y values. The change of bond length of Cu(1)-O(3)-Cu(2) was also measured by Raman spectra. The Raman shift around at 510 cm−1 was associated with Cu(1)-O(3)-Cu(3) axial stretch mode. The Raman shift around at 510 cm−1 for Ba2−xEu1+xCu3O7−δ slightly increased with increasing x values, on the other hand, the shift for Ba2EuCu3O7−y decreased with increasing y values.