Structural and Physical Properties Diversity of New CaCu5-Type Related Europium Platinum Borides

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• 作者：Leonid Salamakha ; Ernst Bauer ; Gerfried Hilscher ; Herwig Michor ; Oksana Sologub ; Peter Rogl ; Gerald Giester
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：April 15, 2013
• 年：2013
• 卷：52
• 期：8
• 页码：4185-4197
• 全文大小：695K
• 年卷期：v.52,no.8(April 15, 2013)
• ISSN：1520-510X

文摘

Three novel europium platinum borides have been synthesized by arc melting of constituent elements and subsequent annealing. They were characterized by X-ray powder and single-crystal diffraction: EuPt₄B, CeCo₄B type, P6/mmm, a = 0.56167(2) nm, c = 0.74399(3) nm; Eu₃Pt₇B₂, Ca₃Al₇Cu₂ type as an ordered variant of PuNi₃, R3̅m, a = 0.55477(2) nm, c = 2.2896(1) nm; and Eu₅Pt₁₈B_6鈥?i>x, a new unique structure type, Fmmm, a = 0.55813(3) nm, b = 0.95476(5) nm, c = 3.51578(2) nm. These compounds belong to the CaCu₅ family of structures, revealing a stacking sequence of CaCu₅-type slabs with different structural units: CaCu₅ and CeCo₃B₂ type in EuPt₄B; CeCo₃B₂ and Laves MgCu₂ type in Eu₃Pt₇B₂; and CaCu₅-, CeCo₃B₂-, and site-exchange ThCr₂Si₂-type slabs in Eu₅Pt₁₈B_6鈥?i>x. The striking motif in the Eu₅Pt₁₈B_6鈥?i>x structure is the boron-centered Pt tetrahedron [BPt₄], which build chains running along the a axis and plays a decisive role in the structure arrangement by linking the terminal fragments of repeating blocks of fused Eu polyhedra. Physical properties of two compounds, EuPt₄B and Eu₃Pt₇B₂, were studied. Both compounds were found to order magnetically at 36 and 57 K, respectively. For EuPt₄B a mixed-valence state of the Eu atom was confirmed via magnetic and specific heat measurements. Moreover, the Sommerfeld value of the specific heat of Eu₃Pt₇B₂ was found to be extraordinarily large, on the order of 0.2 J/mol鈥塊².