Bildung kantenverknüpfter BO₄‐Tetraeder im Hochdruckborat HP‐NiB₂O₄

Abstract

[11][12][13] b-RE 2 B 4 O 9 (RE = Gd, Dy) [14,15] und Pr 4 B 10 O 21 , [16] für die bisher keine entsprechenden Normaldruckmodifikationen bekannt sind. Zu unserer Überra-schung zeigten die Borate RE 4 B 6 O 15 (RE = Dy, Ho) [8][9][10] neben eckenverknüpften BO 4 -Tetraedern erstmals das Strukturmotiv kantenverknüpfter BO 4 -Tetraeder, das bis dahin in der variantenreichen Strukturchemie der Borate fehlte. Im Verlauf unserer Arbeiten entdeckten wir einen zweiten Strukturtyp, a-RE 2 B 4 O 9 (RE = Sm-Ho), [11][12][13] der ebenfalls dieses neue Strukturmotiv aufweist. Hier berichten wir nun erstmals über die Synthese und Charakterisierung eines

Synthesis and Crystal Structure of the High-pressure Iron Borate β-FeB2O4

“…Two new rare-earth borates, α-RE 2 B 4 O 9 (RE = Sm-Ho) [8 -11] and RE 4 B 6 O 15 (RE = Dy, Ho) [8,12,13], exhibit edge-sharing BO 4 tetrahedra, a new structural motif in the chemistry of oxoborates. This motif could also be found in HP-NiB 2 O 4 [14], which is the first borate to show exclusively BO 4 tetrahedra sharing one common edge with a second one. Latest investigations in the system Fe-B-O led to an isotype of the exceptional HP-NiB 2 O 4 , the β -FeB 2 O 4 presented here.…”

“…As already mentioned, the structure of β -FeB 2 O 4 is isotypic to HP-NiB 2 O 4 [14]. Unfortunately, the designation (prefix) is not identical because this nickel borate was identified as the first compound in this structure type.…”

“…Temperature-programmed X-ray powder diffraction experiments were performed on a Stoe Stadi P powder diffractometer [monochromatized MoK α radiation (λ = 71.073 pm)] with a computer-controlled Stoe furnace. The sample was enclosed in a silica capillary and heated from r. t. to 500 • C in 100 • C steps, and from 500 • C to 1100 • C in steps of 50 • C. Afterwards, the sample was cooled to 500 [55], and ∆ o (HP-NiB 2 O 4 ) = 8620 cm −1 [14]. Apparently, there is a slightly higher ligand-field splitting in the borates.…”

“…We now report the synthesis of a second polymorph of FeB 2 O 4 , β -FeB 2 O 4 , its crystal structure, and properties. Furthermore, similarities and differences to the isotypic compound HP-NiB 2 O 4 [14] and other structures are discussed. fied Walker-type multianvil apparatus.…”

Synthesis and Crystal Structure of the High-pressure Cobalt Borate HP-CoB2O4

“…In these examples, only 1 /3 (RE 4 B 6 O 15 (RE = Dy, Ho)) or 1 /10 (α-RE 2 B 4 O 9 (RE = Sm-Ho)) of the BO 4 tetrahedra bridge to a second tetrahedron via a common edge. In the last three years, we could synthesize two isotypic borates, in which all BO 4 tetrahedra share a common edge with a second tetrahedron: HP-NiB 2 O 4 [10] and β -FeB 2 O 4 [11]. Up to now, we cannot predict the occurrence of edge-sharing BO 4 0932-0776 / 10 / 1100-1311 $ 06.00 c 2010 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com tetrahedra.…”