Compositional evolution of the NaZn13 structure motif in the systems La-Ni-Ga and Ce-Ni-Ga

Dalton Transactions : an International Journal of Inorganic Chemistry
Yurii ProtsYuri Grin

Abstract

Phase relationship and structural behaviour in the substitutional series LaNi13-xGax and CeNi13-xGax have been studied by a combination of X-ray powder diffraction measurements, differential scanning calorimetry, electron diffraction tomography and metallographic analyses. The sequence of morphotropic phase transformations has been found in the series LaNi13-xGax resulting in five varieties of the NaZn13 structure: the cubic phase with aristotype structure at x = 2 (space group Fm3[combining macron]c, Pearson symbol cF112), two tetragonal phases at x = 2.5-4.25 (space group I4/mcm, Pearson symbol tI56-I) and 7-7.5 (space group I4/mcm, Pearson symbol tI56-II), both with an atomic arrangement of the CeNi8.5Si4.5 type and two orthorhombic phases at x = 4.5-5.75 (LaNi7In6 structure type, space group Ibam, Pearson symbol oI56) and x = 6.37-6.87 (a new derivative of the NaZn13, prototype structure, space group Fmmm, Pearson symbol oF112). The related series CeNi13-xGax shows similar behaviour. The corresponding tI56-I ↔oI56 ↔oF112 ↔tI56-II phases are formed at x = 4-4.25, 4.5-6, 6.37-6.87 and 7-7.37, respectively. In contrast to the lanthanum analogues, the phase with cubic symmetry was not found for this system. Complex twinned and ...Continue Reading

References

Feb 2, 2002·Chemistry : a European Journal·Y M KalychakR Pöttgen
Dec 25, 2007·Acta Crystallographica. Section A, Foundations of Crystallography·George M Sheldrick
Jun 10, 2009·Journal of Physics. Condensed Matter : an Institute of Physics Journal·L PeykerH Michor

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Methods Mentioned

BETA
X-ray
electron diffraction
thermal treatment

Software Mentioned

WinCSD
ADT3D
SHELXL
SIR2011

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