The Ce-Ni-Si System Revisited: More Homologue Compounds?

Area of Science:

• Materials Science
• Solid State Chemistry
• Crystallography

Background:

• The Ce-Ni-Si ternary system is of interest for its diverse intermetallic compounds.
• Previous studies have identified various phases, but the nickel-rich region requires further investigation.

Purpose of the Study:

• To comprehensively reinvestigate the nickel-rich region of the Ce-Ni-Si system.
• To identify and characterize novel compounds and structural types within this system.

Main Methods:

• Utilized X-ray single-crystal, powder, and electron diffraction techniques.
• Employed electron microprobe and thermal analyses for characterization.
• Performed Rietveld refinement and single-crystal X-ray diffraction for structure determination.

Main Results:

• Identified two new hexagonal compounds: τ-Ce₂₀₊Ni₃₆₊Si_30- and τ'-Ce₃₀₊Ni₅₀₊Si_42-.
• Determined the crystal structure of τ-Ce₂₀₊Ni₃₆₊Si_30- (Sm₁₀Ni_20.8P₁₅-type) and τ'-Ce₃₀₊Ni₅₀₊Si_42- (Tb₁₅Ni₂₈P₂₁-type).
• Discovered a novel monoclinic structure type for Ce₃Ni₄Si₂, belonging to a new homologous series RE_(3×2Ni_(3×2Si₍₂ in RE-Ni-Si systems.

Conclusions:

• The reinvestigation successfully expanded the knowledge of the Ce-Ni-Si phase diagram, particularly in the nickel-rich region.
• The discovery of novel compounds and a new homologous series provides insights into structure-property relationships in RE-Ni-Si materials.
• The structural characterization reveals unique features like corner-sharing Si-polyhedral blocks and zigzag nickel chains.