The system Ce-Zn-Si for <33.3% at. Ce

Author(s)

Fainan Failamani, Andrij Grytsiv, Raimund Podloucky, Herwig Michor, Ernst Bauer, Pavel Broz, Gerald Giester, Peter Franz Rogl

Abstract

Phase equilibria of the system Ce-Zn-Si have been determined for the isothermal section at 600 °C for <33.3 at.% Ce by XRPD and EPMA. This partial section is characterized by the formation of five ternary compounds with homogeneity regions at constant Ce-content and partial substitution of Zn/Si: τ₁-Ce₇Zn₂₁(Zn_1-xSi_x)₂ (unique type; 0.45 ≤ x ≤ 0.99), τ₂-Ce(Si_1-xZn_x)₂ (AlB₂-type; 0.36 ≤ x ≤ 0.73), τ₅-CeZn(Zn_1-xSi_x)₂ (CeNiSi₂-type; 0.68 ≤ x ≤ 0.76), τ₆-CeZn₂(Si_1-xZn_x)₂ (ThCr₂Si₂-type; 0.25 ≤ x ≤ 0.30) and τ₇-Ce₃₇Zn₄₈Si₁₅ (structure unknown). Whereas τ₁, τ₂ and τ₅ are stable at 600 and 800°C, the phases τ₆, τ₇ are unstable at 800°C. Atom site distribution in the crystal structures of τ₅, τ₆ and {La,Ce}₇Zn₂₁(Zn_1-xGe_x)₂ have been elucidated from X-ray intensity refinements on single crystals. The small amounts of the stabilizing tetrel element in {La,Ce}₇Zn₂₁[Zn_1-xSi(Ge)_x]₂ suggest a hypothetical binary phase "{La,Ce}₇Zn₂₃". The stabilizing effect of Ge in Ce₇Zn_23-xGe_x has been elucidated from density functional theory (DFT) calculations discussing the electronic structure in terms of the density of states (DOS) and defining enthalpies of formation for Ce₇Zn_23-xGe_x (x = 0, 0.5, 2) as well as for several neighbouring binary Ce-Zn phases. A Schultz-Scheil diagram for the solidification behaviour in the (Zn,Si)-rich part of the diagram was constructed from DTA measurements in closed silica crucibles along with partial isothermal sections determined in the temperature range from 400 to 900°C. The phases τ₅ and τ₆ both form in degenerate ternary peritectic reactions: L + CeSi₂,β-Ce₂Zn₁₇ ζ τ₅ at 865 ± 5°C and L + τ₅,CeZn₁₁ ζ τ₆ at 695 ± 5°C, respectively. Magnetic susceptibility, specific heat and resistivity measurements of τ₅-CeZn(Zn_1-xSi_x)₂ revealed Kondo lattice behavior with ferromagnetic ordering below T_C = 4.4 K, whereas susceptibility and specific heat studies of τ₆-CeZn₂(Zn_0.28Si_0.72)₂ revealed Curie-Weiss paramagnetic behaviour down to 3 K. The effective paramagnetic moments of Ce obtained from Curie-Weiss fits of τ₅ (2.50μ_B) and τ₆ (2.34μ_B) reveal a ground state close to trivalent Ce.

Organisation(s)

Department of Physical Chemistry, Department of Mineralogy and Crystallography

External organisation(s)

Technische Universität Wien, Masaryk University

Journal

RSC Advances

Volume

5

Pages

36480-36497

No. of pages

18

ISSN

2046-2069

DOI

https://doi.org/10.1039/c5ra02789f

Publication date

03-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

104017 Physical chemistry, 104011 Materials chemistry, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Chemical Engineering(all), Chemistry(all)

Portal url

https://ucrisportal.univie.ac.at/en/publications/the-system-ceznsi-for-333-at-ce(9c43ad5c-7318-4bba-b56e-542a8add20fe).html