Failamani, Fainan;
Grytsiv, Andriy;
Podloucky, Raimund;
Michor, Herwig;
Bauer, Ernst;
Broz, Pavel;
Giester, Gerald;
(2015)
The system Ce–Zn–Si for <33.3 at.% Ce: phase relations, crystal structures and physical properties.
RSC ADVANCES
, 5
pp. 36480-36497.
10.1039/c5ra02789f.
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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(Zn₁₋ₓSiₓ)₂ (unique type; 0.45 ≤ ₓ ≤ 0.99), τ₂-Ce(Si₁₋ₓZnₓ)₂ (AlB₂-type; 0.36 ≤ ₓ ≤ 0.73), τ₅-CeZn(Zn₁₋ₓSiₓ)₂ (CeNiSi₂-type; 0.68 ≤ ₓ ≤ 0.76), τ₆-CeZn₂(Si₁₋ₓZnₓ)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(Zn₁₋ₓGeₓ)₂ have been elucidated from X-ray intensity refinements on single crystals. The small amounts of the stabilizing tetrel element in {La,Ce}₇Zn₂₁[Zn₁₋ₓSi(Ge)ₓ]₂ suggest a hypothetical binary phase “{La,Ce}₇Zn₂₃”. The stabilizing effect of Ge in Ce₇Zn₂₃₋ₓGeₓ 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 Ce₇Zn₂₃₋ₓGeₓ (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 ⇔ τ₅ at 865 ± 5 °C and L + τ₅, CeZn₁₁ ⇔ τ₆ at 695 ± 5 °C, respectively. Magnetic susceptibility, specific heat and resistivity measurements of τ₅-CeZn(Zn₁₋ₓSiₓ)₂ revealed Kondo lattice behavior with ferromagnetic ordering below T꜀ = 4.4 K, whereas susceptibility and specific heat studies of τ₆-CeZn₂(Zn₀.₂₈Si₀.₇₂)₂ revealed Curie–Weiss paramagnetic behaviour down to 3 K. The effective paramagnetic moments of Ce obtained from Curie–Weiss fits of τ₅ (2.50 μB) and τ₆ (2.34 μB) reveal a ground state close to trivalent Ce.
| Type: | Article |
|---|---|
| Title: | The system Ce–Zn–Si for <33.3 at.% Ce: phase relations, crystal structures and physical properties |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/c5ra02789f |
| Publisher version: | https://doi.org/10.1039/c5ra02789f |
| Language: | English |
| Additional information: | © The Author(s), 2025. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. https://creativecommons.org/licenses/by/3.0/ |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10211361 |
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