Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-23T14:47:50.106Z Has data issue: false hasContentIssue false
  • English
  • Français

Positional ordering in the light RE–Ga systems (RE=rare earth element)

Published online by Cambridge University Press:  10 January 2013

D. Gur  and
G. Kimmel
D. Gur
Affiliation:
Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
G. Kimmel
Affiliation:
Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
Get access Rights & Permissions [Opens in a new window]

Abstract

Crystal data and results of structure refinement, using powder X-ray diffraction and Rietveld analysis, for ε-ordered structures near 75 at. % Ga are reported. The structures are based on the AlB2-type with deviation from stoichiometry due to pairwise substitution of rare earth (RE) atoms by gallium. Weak reflections which are forbidden in the AlB2-type structure were observed and indicate the existence of positional ordering of Ga2 pairs located in the basal planes preserving the hexagonal symmetry (S.G. P6/mmm). This ordering results in a new unit cell with parameters a′, c′, in which a′=a√3 and c′=c. The experimental data of the cells parameters are: a=7.467(2)Å, c=4.276(3)Å for Nd1−xGa2−x (x=0.18), and a=7.400(3)Å, c=4.184(2)Å for Gd1−xGa2+2x (x=0.165).

Type
Research Article
Information
Powder Diffraction , Volume 14 , Issue 2 , June 1999 , pp. 122 - 125
Copyright
Copyright © Cambridge University Press 1999

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Gur, D., Kimmel, G., and Dirnfeld, S. F. (1993). “XRPD of New Intermediate Phases in Gd–Ga and Nd–Ga Systems,” Mater. Sci. Forum 133–136, 479–484.CrossRefGoogle Scholar
Hill, R. J., and Madsen, I. C. (1986). “The Effect Of Profile Step Width on the Determination of Crystal Structure Parameters and Estimated Standard Deviations by X-Ray Rietveld Analysis,” J. Appl. Crystallogr. 19, 10–18.CrossRefGoogle Scholar
Howard, C. J., and Hill, R. J. (1986). “A Computer Program for Rietveld Analysis of Fixed Wavelength X-Ray and Neutron Powder Diffraction Patterns,” Australian Atomic Energy Commission Report No. M112.Google Scholar
Kaplan, W. D., and Kimmel, G. (1990). “Order and Disorder of Phases in Gallium Rich Gallium–Lanthanum Alloys,” Acta Crystallogr., Sect. A: Found. Crystallogr. A46, 281.Google Scholar
Kaplan, W. D., and Kimmel, G. (1992). “Rietvelt Analysis and Pairwise Substitutional Alloys,” Adv. X-Ray Anal. 35a, 63–68.Google Scholar
Kaplan, W. D., and Kimmel, G. (1996). “Ordered LaGa 4 and its Relation to other Structures in the Ga–La Binary System,” J. Alloys Compd. 232, 126–132.CrossRefGoogle Scholar
Kimmel, G., Dayan, D., Grill, A., and Pelleg, J. (1980). “The Gallium Rich Side of Nd–Ga and Ce–Ga Systems,” J. Less-Common Met. 75, 133–140.CrossRefGoogle Scholar
Kimmel, G., Dayan, D., Zevin, L., and Pelleg, J. (1985). “The Structure of R 1−xGa 2+2x (0<x<.33) and its relation to RGa 6 and Ga,” Metall. Trans. A 16, 167–171.CrossRefGoogle Scholar
Kimmel, G., and Kaplan, W. D. (1991). “A New Phase Transition Phenomenon in Gallium-Lanthanides,” Scr. Metall. Mater. 25, 571–574.CrossRefGoogle Scholar
Kimmel, G., and Schreiner, W. N. (1988). “Accuracy in Temperature Factors Determination in Powder Diffractometry,” Aust. J. Phys. 41, 719–728.CrossRefGoogle Scholar
Pelleg, J., Kimmel, G., and Dayan, D. (1981). “RGa 6 (R=Rare Earth Atom), A Common Intermetallic Compound of the R–Ga System,” J. Less-Common Met. 81, 33–44.CrossRefGoogle Scholar
Pelleg, J., Zevin, L., Kimmel, G., and Dayan, D. (1985). “Recent Advances in the Rare Earth-Gallium Systems,” J. Less-Common Met. 110, 91–97.CrossRefGoogle Scholar
Wiles, D. B., and Young, R. A. (1981). “A New Computer Program for Rietveld Analysis of XRPD Patterns,” J. Appl. Crystallogr. 14, 149–151.CrossRefGoogle Scholar
Zevin, L., Pelleg, J., Kimmel, G., and Dayan, D. (1984). “Positional and Orientational Ordering in La 1−xGa 2+2x and Formation of LaGa 4,”Scr. Metall. 18, 1257–1261.CrossRefGoogle Scholar