The isothermal cross-section of the phase diagram of the ternary Tb-Hf-Si system at 873 K was constructed. The formation of two compounds was established: Tb 2 Hf 3 Si 4 (Sc 2 Re 3 Si 4 type, P4 1 2 1 2, tP36, Z = 4; a = 0.72057(8), c = 1.3199(2) nm) and (Tb 0.7 Hf 0.3)Si (CrB type, Cmcm, oS8, Z = 4; a = 0.42241(8), b = 1.0483(2), c = 0.38227(7) nm).
The crystal structure of the (Cr,Ni)4Si phase with and without Co was refined from X-ray powder diffraction data. The compound crystallises with an Au4Al-type structure (Pearson symbol cP20, space group P213): unit-cell parameter a = 0.611959(6) nm for the composition (Cr0.312Ni0.688)4Si, a = 0.612094(6) nm for (Cr0.375Ni0.625)4Si, and a = 0.612316(6) nm for (Cr0.337Co0.063Ni0.600)4Si. The magnetic susceptibility was measured in external fields up to 7 T at temperatures between 1.8 and 400 K. The three investigated samples exhibited paramagnetic behaviour described by the modified Curie-Weiss law: χ0 = 146∙10-6 emu g-at.-1, μeff = 0.21 μB/atom, θP = -13 K for (Cr0.312Ni0.688)4Si; χ0 = 158∙10-6 emu g-at.-1, μeff = 0.20 μB/atom, θP = -15 K for (Cr0.375Ni0.625)4Si; χ0 = 169∙10-6 emu g-at.-1, μeff = 0.18 μB/atom, θP = -52 K for (Cr0.337Co0.063Ni0.600)4Si.
The crystal structures of Tb(Al 0.15 Si 0.85 ), (Tb 0.70 Zr 0.30 )(Al 0.17 Si 0.83 ) and Zr(Al 0.22 Si 0.78 ) have been refined from single-crystal X-ray diffraction data. The three compounds crystallize with CrB-type structures (Pearson symbol oS8, space group Cmcm): Tb(Al 0.15 Si 0.85 ): a ϭ 4.2715(5), b ϭ 10.5595(15), c ϭ 3.8393(5) Å ; (Tb 0.70 Zr 0.30 )(Al 0.17 Si 0.83 ): a ϭ 4.163(2), b ϭ 10.423(5), c ϭ 3.8543(18) Å ; Zr(Al 0.22 Si 0.78 ): a ϭ 3.7824(6), b ϭ 10.0164(16), c ϭ 3.7795(5) Å . The existence of a significant CrB-type solid solu- IntroductionCrB, Strukturbericht notation B f (or α-TlI, B33), Pearson symbol oS8, is one of the most common structure types of inorganic compounds. Only among binary compounds, 128 representatives of this orthorhombic type are reported in [1]. Two Wyckoff positions 4(c) of the space group Cmcm are occupied by larger (chromium in CrB, iodine in α-TlI) and smaller (boron or thallium) atoms, respectively. Compounds with this structure type also occur in ternary systems, either at 50 at.% of an element with larger atomic radius and two elements of smaller radius forming a statistical mixture, or at 50 at.% of an element with smaller atomic radius and two elements of larger radius forming a statistical mixture.The crystal structures of the equiatomic compounds observed in the binary systems of the rare-earth metals with silicon are summarized in Tables 1 and 2. The silicides RESi where RE is a heavy rare-earth element crystallize with CrB-type structures, whereas the light rare-earth metals, except Eu, form compounds with FeB-type structures (Pearson symbol oP8, space group Pnma) at the same composition. The monosilicides of Dy, Er and Ho are dimorphic, the structure of the high-temperature modification corresponding to the CrB type. LaSi is also dimorphic, however, the low-temperature modification of the LaSi phase adopts a different structure (own type, oS16, Cmcm). No binary rare-earth aluminides REAl crystallize with the
The structures of the compounds Pr 5 Si 3 and Zr 3 Si 2 were refined on X-ray single-crystal diffraction data. Pr 5 Si 3 crystallizes with the tetragonal structure type Cr 5 B 3 : space group I4/mcm, Pearson symbol tI32, a = 0.7820(1), c = 1.3812(3) nm, Z = 4, R1 = 0.035, wR2 = 0.080 for 287 unique reflections, 16 refined parameters. Zr 3 Si 2 crystallizes with the tetragonal structure type U 3 Si 2 : Pearson symbol tP10, space group P4/mbm, a = 0.7087(1), c = 0.37060(7) nm, Z = 2, R1 = 0.022, wR2 = 0.042 for 114 unique reflections, 12 refined parameters.
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