Synthesis and Crystal Structure of New Ce–Ru–Ga Ternary Intermetallic Phases with Known Structure Types

Resumo

Five new intermetallic phases of known structure types have been identified in a systematic study of the Ce–Ru–Ga system: CeRu_0.90Ga_1.10 (MgZn₂ structure, sp. gr. Р6₃/mmc, а = 5.44503(5) Å, с = 8.67188(13) Å, very narrow homogeneity range), Ce₇Ru₆Ga₇ (Pr₇Co₆Al₇ structure, constant composition, sp. gr. Р4/mbm, а = 13.61910(17) Å, с = 4.34957(5) Å), Ce₆Ru_0.18Ga_2.82 (K₂UF₆-derived structure, sp. gr. P\(\bar {6}\)2m, a = 8.09628(19) Å, c = 4.38470(13) Å), Ce₂₃Ru₁₀Ga (Pr₂₃Ir₇Mg₄ structure, sp. gr. P6₃mc, а = 9.867(6) Å, с = 22.153(14) Å) and Ce₂₆(Ru_0.59Ga_0.41)₁₇ (Sm₂₆(Co_0.65Ga_0.35)₁₇ structure, sp. gr. P4/mbm, a = 11.9529(4) Å, c = 15.0135(10) Å). In the structures of Ce₇Ru₆Ga₇, Ce₂₃Ru₁₀Ga, and Ce₂₆(Ru_0.59Ga_0.41)₁₇, some of the Ce atoms form very short Ce–Ru bonds (2.525(3), 2.549(5), and 2.506(2) Å, respectively), which is attributable to their intermediate valence state.