Kristallstrukturuntersuchungen an den Alkali- und BariumÜbergangsmetallfluoriden RbK2Mn2F7, BaNiF4 und einer 5 : 3-Phase im System BaLiF3/NaCoF3 |
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Authors: | M. Welsch,S. Kummer-Dö rner,B. Peschel,D. Babel |
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Abstract: | Crystal Structural Studies of the Alkali and Barium Transition Metal Fluorides RbK2Mn2F7, BaNiF4, and a 5 : 3-Phase of the System BaLiF3/NaCoF3 At single crystals of the compounds RbK2Mn2F7, BaNiF4, and of a phase 0.618 BaLiF3/0.382 NaCoF3 the X-ray crystal structures were refined. RbK2Mn2F7 is tetragonal (a = 421.1(1), c = 2188.3(2) pm, I4/mmm, Z = 2) and belongs to the Sr3Ti2O7 type. The average distances are Mn–F: 210.7 pm for the [MnF6] octahedron and A–F: 290.6 resp. 297.1 pm for the [AF9] resp. [AF12] coordination of the mixed alkali positions (A = Rb/3 + 2 K/3). BaNiF4 (a = 413.7(1), b = 1443.1(3), c = 578.1(1) pm, Cmc21, Z = 4) is of the orthorhombic BaZnF4 type; Ni–F: 200.3 pm, Ba–F: 274.3 pm for CN6 and CN9, resp.. The phase of approximate composition 5 : 3, isolated from a 1 : 1 batch BaLiF3/NaCoF3, is cubic (a = 801.8(1) pm, Im3, Z = 8 AMF3) and forms a strongly disordered perovskite super-structure, the features of which are discussed. |
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Keywords: | Structure determination fluorides of manganese(II), cobalt(II), nickel(II) RbK2Mn2F7 BaNiF4 BaLiF3/NaCoF3 phase solid solution perovskite disorder |
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