Powder X-Ray Reference Patterns of Sr2RGaCu2Oy (R = Pr Nd Sm Eu Gd Dy Ho Er Tm and Y)

摘要

X-Ray Rietveld refinements were conducted on a series of eleven lanthanide phases, Sr2RGaCu2Oy (2112 phase, R = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, and Yb) that are structurally related to the high Tc superconductor Ba2YCu3O7 (213). In the 2112 structure, instead of square planar Cu-O chains, tetrahedral GaO4 chains were found to run in a zig-zag fashion along the diagonal of the basal 213 ab-direction. Reference powder patterns for these compounds were prepared by using the Rietveld decomposition technique. The unit cell volume of these compounds follows the expected trend of the lanthanide contraction. The lattice parameters range from a = 22.9694(3) Å, b = 5.5587(2) Å, and c = 5.44743(7) Å for R = Pr, to a = 22.8059(2) Å, b = 5.46031(5) Å, and c = 5.37773(5) Å for R = Yb. An electon diffraction study of the Sm- and Er-analogs showed characteristic diffuse streaks along the b-axis, suggesting some disorder within the GaO4 chains.