Original Oxo-Centered Frameworks in Bi₃(VO₄)O₃ and Bi_3.5(AsO₄)(OH)_0.5O_3.5 by Supercritical Steam

Abstract

Two new bismuth compounds, oxovanadate Bi 3 (VO 4 )O 3 and oxoarsenate Bi 3.5 (AsO 4 )(OH) 0.5 O 3.5 , were prepared using supercritical hydrothermal pressure. Dealing with the anionic sublattice, both crystal structures are built on anti-oxo-OBi 4 / OBi 3 or -OBi 4 /OBi 5 units connected together in infinite corrugated 2D layers surrounded by isolated XO 4 (X = V or As) tetrahedra. These edifices complete a series initiated by the recent Bi 3 (PO 4 )O 3 prepared under similar conditions. With the latter being assigned to the "simplest" bioxophosphate in terms of structural complexity, this aspect was investigated among the other compounds in their chemical ternaries. These phases are suggested to be high-pressure polymorphs, not possible to tackle when working at ambient pressure and temperature conditions.

Novel bismuth oxosalts, β-Bi3O3(VO4) and KBi5O5(PO4)2: synthesis and effect of hydrothermal pressure on the crystal structure

“…Note that the structure of Bi 3 O 3 (PO 4 ) is the simplest one among the structures of known bismuth oxophosphates. 13 As shown for the structure of α-Bi 3 O 3 (VO 4 ), 4 I G,total equals 196.22 bits per cell. Thus α- and β-Bi 3 O 3 (VO 4 ) occupy intermediate positions on the crystal structure complexity among bismuth vanadates, for which the I G,total parameters vary in the range of 24.054–1016.355 bits per cell.…”

“…The crystal structure of KBi 5 O 5 (PO 4 ) 2 shows a similarity to the structure of high-temperature modification of oxovanadate α-Bi 3 O 3 (VO 4 ). 4 The structural relationship between KBi 5 O 5 (PO 4 ) 2 and α-Bi 3 O 3 (VO 4 ) is based on their origin from the structural type of the fluorite-like δ-Bi 2 O 3 oxide. Topologically identical 1D metal–oxygen fragments are clearly visible in the xz and yz projections of KBi 5 O 5 (PO 4 ) 2 and α-Bi 3 O 3 (VO 4 ) crystal structures, respectively (Fig.…”

“…Thus compound (I) was obtained as the main phase at a calculated pressure of more than 180 bar. At this pressure, needle-shaped crystals of another modification of bismuth vanadate, α-Bi 3 O 3 (VO 4 ), 4 were also identified in minor amount.…”

“…Substitution in this parent structure of Bi with metal cations and anionic groups (PO 4 and VO 4 ) results in a variety of novel compounds, as has been shown in a number of works. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The structural relationship between the members of the discussed family is based on the description of their polycationic fragments formed by O(Bi,M) n polyhedra. Thus chain, ribbon and layered [Bi-M-O] n+ polycations were described.…”

“…Recently, a number of studies have focused on the design of new Bi-based oxosalts using the hydrothermal technique. Thus Bi 3 O 3 (PO 4 ) 13 and its isoformular Bi 3 O 3 (VO 4 ) 4 oxophosphate, with the simplest chemical compositions, were synthesized under supercritical hydrothermal pressure. In search of new low dimensional magnets, Ni-based oxophosphates, Bi 2 Ni (PO 4 )O 2 (OH) 14 and KBi 4 Ni 2 (PO 4 ) 3 O 4 , 16 were obtained also under hydrothermal conditions.…”