Pt鈥揃 System Revisited: Pt2B, a New Structure Type of Binary Borides. Ternary WAl12-Type Derivative Borides

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• 作者：Oksana Sologub ; Leonid Salamakha ; Peter Rogl ; Berthold St枚ger ; Ernst Bauer ; Johannes Bernardi ; Gerald Giester ; Monika Waas ; Robert Svagera
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 16, 2015
• 年：2015
• 卷：54
• 期：22
• 页码：10958-10965
• 全文大小：456K
• ISSN：1520-510X

文摘

On the basis of a detailed study applying X-ray single-crystal and powder diffraction, differential scanning calorimetry, and scanning electron microscopy analysis, it was possible to resolve existing uncertainties in the Pt-rich section (鈮?5 atom % Pt) of the binary Pt鈥揃 phase diagram above 600 掳C. The formation of a unique structure has been observed for Pt₂B [X-ray single-crystal data: space group C2/m, a = 1.62717(11) nm, b = 0.32788(2) nm, c = 0.44200(3) nm, 尾 = 104.401(4)掳, R_F2 = 0.030]. Within the homogeneity range of 鈥淧t₃B鈥? X-ray powder diffraction phase analysis prompted two structural modifications as a function of temperature. The crystal structure of 鈥?i>hT-Pt₃B鈥?complies with the hitherto reported structure of anti-MoS₂ [space group P6₃/mmc, a = 0.279377(2) nm, c = 1.04895(1) nm, R_F = 0.075, R_I = 0.090]. The structure of the new 鈥?img src="/appl/literatum/publisher/achs/journals/content/inocaj/2015/inocaj.2015.54.issue-22/acs.inorgchem.5b01998/20151110/images/ic-2015-01998v_m001.gif" alt="" />T-Pt₃B鈥?is still unknown. The formation of previously reported Pt_鈭?B has not been confirmed from binary samples. Exploration of the Pt-rich section of the Pt鈥揅u鈥揃 system at 600 掳C revealed a new ternary compound, Pt₁₂CuB_6鈥?i>y [X-ray single-crystal data: space group Im3虆, a = 0.75790(2) nm, y = 3, R_F2 = 0.0129], which exhibits the filled WAl₁₂-type structure accommodating boron in the interstitial trigonal-prismatic site 12e. The isotypic platinum鈥揳luminum鈥揵oride was synthesized and studied. The solubility of copper in binary platinum borides has been found to attain 鈭? atom % Cu for Pt₂B but to be insignificant for 鈥?img src="/appl/literatum/publisher/achs/journals/content/inocaj/2015/inocaj.2015.54.issue-22/acs.inorgchem.5b01998/20151110/images/ic-2015-01998v_m002.gif" alt="" />T-Pt₃B鈥? The architecture of the new Pt₂B structure combines puckered layers of boron-filled and empty [Pt₆] octahedra (anti-CaCl₂-type fragment) alternating along the x axis with a double layer of boron-semifilled [Pt₆] trigonal prisms interbedded with a layer of empty tetrahedra and tetragonal pyramids (B-deficient 伪-TI fragment). Assuming boron vacancies ordering (space group R3), the Pt₁₂CuB_6鈥?i>y structure exhibits serpentine-like columns of edge-connected boron-filled [Pt₆] trigonal prisms running infinitely along the z axis and embedding the icosahedrally coordinated Cu atom. Pt₂B, (Pt_1鈥?i>yCu_y)₂B (y = 0.045), and Pt₁₂CuB_6鈥?i>y (y = 3) behave metallically, as revealed by temperature-dependent electrical resistivity measurements.