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Powder X-Ray Reference Patterns of Sr 2 RGaCu 2 O y (R = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y)

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ABSTRACT

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.

No MeSH data available.


Selected area (electron) diffraction (SAD) patterns of Sr2SmGaCu2Oy showing various zone-axis orientations. Continuous streaks of diffuse intensity along the b-direction is observed in the [100] zone-axis pattern.
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f6-j64won: Selected area (electron) diffraction (SAD) patterns of Sr2SmGaCu2Oy showing various zone-axis orientations. Continuous streaks of diffuse intensity along the b-direction is observed in the [100] zone-axis pattern.

Mentions: 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. A set of selected area (electron) diffraction (SAD) patterns for the R = Sm sample is illustrated in Fig. 6. In addition to the strong fundamental reflections, the pattern of the [100] zone axis exhibits continuous streaks of diffuse intensity along the b-direction. Formation of a superstructure with a doubled periodicity along the c-direction has been reported for the Sr2YCoCu2O7 and Sr2 (Nd,Ce)2GaCu2O9 compounds by Krekels et al. [13]. However, in the present study, no such doubling was observed. The observed streaks can be attributed to a disorder due to presence of oxygen vacancies and/or copper atoms within tetrahedral GaO4 chains extending along the b-direction, similar to that described by Krekels et al. [12]. X-ray diffraction, however, is not as sensitive as neutron diffraction to the disorder of light elements such as oxygen, as reflected in relatively small values (≈ 0.004 Å) of the refined isotropic temperature factors (Uiso).


Powder X-Ray Reference Patterns of Sr 2 RGaCu 2 O y (R = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y)
Selected area (electron) diffraction (SAD) patterns of Sr2SmGaCu2Oy showing various zone-axis orientations. Continuous streaks of diffuse intensity along the b-direction is observed in the [100] zone-axis pattern.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862828&req=5

f6-j64won: Selected area (electron) diffraction (SAD) patterns of Sr2SmGaCu2Oy showing various zone-axis orientations. Continuous streaks of diffuse intensity along the b-direction is observed in the [100] zone-axis pattern.
Mentions: 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. A set of selected area (electron) diffraction (SAD) patterns for the R = Sm sample is illustrated in Fig. 6. In addition to the strong fundamental reflections, the pattern of the [100] zone axis exhibits continuous streaks of diffuse intensity along the b-direction. Formation of a superstructure with a doubled periodicity along the c-direction has been reported for the Sr2YCoCu2O7 and Sr2 (Nd,Ce)2GaCu2O9 compounds by Krekels et al. [13]. However, in the present study, no such doubling was observed. The observed streaks can be attributed to a disorder due to presence of oxygen vacancies and/or copper atoms within tetrahedral GaO4 chains extending along the b-direction, similar to that described by Krekels et al. [12]. X-ray diffraction, however, is not as sensitive as neutron diffraction to the disorder of light elements such as oxygen, as reflected in relatively small values (≈ 0.004 Å) of the refined isotropic temperature factors (Uiso).

View Article: PubMed Central - PubMed

ABSTRACT

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.

No MeSH data available.