CrB‐Type Phases in the Tb‐Zr‐Al‐Si System

Abstract

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 Tb–Hf–Si system at 873 K

“…During the investigation of the ternary Tb-Hf-Si system at 873 K we confirmed the existence and structure type of the following binary compounds: The isothermal cross-section of the Tb-Hf-Si system at 873 K is shown in Fig. 1 [27]). We cannot exclude the existence of a small homogeneity range for the compound (Tb 0.7 Hf 0.3 )Si with CrB structure type.…”

The Tb‒Hf‒Al‒Si system (600 C)

“…Tb(Al 0,15 Si 0,85 ) [10] та HfAl [12] (структурний тип TlI, символ Пірсона oS8, просторова група Cmcm) Table 4 Interatomic distances in the structures of the compounds (Tb 0.74 Hf 0.26 )(Al 0.48 Si 0.52 ), (Tb 0.7 Hf 0.3 )Si [6],…”

“…Tb(Al 0.15 Si 0.85 ) [10], and HfAl [12] Keywords: Tb-Hf-Al-Si system, X-ray diffraction, energy-dispersive X-ray analysis, solid solution, TlI structure type.…”