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


Phase relationship and structural behaviour in the substitutional series LaNi13–xGax and CeNi13–xGax has been studied by a combination of X-ray powder diffraction measurements, differential scanning calorimetry, electron diffraction tomography and metallographic analyses. The sequence of the 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 Fm 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 (new derivative of 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 analogous, the phase with cubic symmetry was not found for this system. Complex twinned and multiple twinned (twinning of twins) domain structures which are revealed for the tetragonal and both orthorhombic phases clearly indicate the temperature-induced polymorphic phase transitions during the formation of these phases. LaNi13–xGax samples show paramagnetic behavior, whereas the CeNi13–xGax series exhibits Curie-Weiss paramagnetism.

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Publication details

The article was received on 03 Jun 2018, accepted on 06 Aug 2018 and first published on 07 Aug 2018

Article type: Paper
DOI: 10.1039/C8DT02273A
Citation: Dalton Trans., 2018, Accepted Manuscript
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    Compositional evolution of the NaZn13 structure motif in the systems La–Ni–Ga and Ce–Ni–Ga

    Y. Prots, L. Vasylechko, W. Carrillo-Cabrera, C. Drathen, M. Coduri , D. Kaczorowski, U. Burkhardt and Y. Grin, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C8DT02273A

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