Crystal Structures of Ca-Free Pb2Sr2RCu3O8 (R = La, Pr, Nd, Eu, Tb, and Dy) Single Crystals

Structures of Pb2Sr2RCu3O8 have been determined by single crystal X-ray diffraction. A monoclinic symmetry (C2/m, Z = 2) was found for those crystals with R = Pr, Nd, and Tb, orthorhombic (Cmmm, Z = 2) for R = La, and tetragonal (P4/mmm, Z = 1) for R = Eu and Dy. The relationship among different crystal symmetries can be understood in terms of different oxygen orderings in the PbO layers driven by the Ph2+ lone pair orientation. There is …