X-ray and neutron powder diffraction studies of Ba(NdxY2−x)CuO5

Ba(R,R′)2CuO5 (R,R′=lanthanides and Y) plays an important role as a flux-pinning agent in enhancing the superconducting properties of the Ba2(R,R′)Cu3O6+x (R,R′=lanthanides and Y) coated conductors. Using X-ray diffraction and neutron diffraction, we found that the Ba(NdxY2−x)CuO5 solid solution adopts two structure types. In the Nd-rich region (1.8⩽x⩽2.0), the materials are of brown color (commonly referred to as the ‘brown phase’), and the structure is tetragonal with space group I4/mbm (no. 127). In the Y-rich region (0.0⩽x⩽1.4), the materials are green (commonly referred to as the ‘green phase’) and the structure is orthorhombic with space group Pnma (no. 62). A two-phase region (1.4