Ba[Co₃(VO₄)₂(OH)₂] with a regular Kagomé lattice

Abstract

The new layered title compound, barium di-μ-hydroxido-di-μ-vanadato-tricobaltate(II), was prepared under low-temperature hydrothermal conditions. Its crystal structure comprises Co(2+) and O(2-) ions in the Kagomé geometry. The octahedral Co(3)O(6)(OH)(2) Kagomé layers, made up of edge-shared CoO(4)(OH)(2) octahedra with Co on a site of 2/m symmetry, alternate along the c axis with barium vanadate heteropolyhedral layers, in which Ba is on a site of 3m symmetry and V is on a site of 3m symmetry. All three O atoms and the H atom also occupy special positions: two O atoms and the H atom are on sites with 3m symmetry and one O atom is on a site with m symmetry. Ba[Co(3)(VO(4))(2)(OH)(2)] represents the first compound from the four-component BaO-CoO-V(2)O(5)-H(2)O system and its structure is topologically related to the minerals vesignieite, Ba[Cu(3)(VO(4))(2)(OH)(2)], and bayldonite, Pb[Cu(3)(AsO(4))(2)(OH)(2)].

Nanocrystalline BaCo3(VO4)2(OH)2 with a kagome lattice of Co(ii) ions: synthesis, crystal structure and magnetic properties

“…The purity and crystallinity of the sample were confirmed by PXRD analysis at room temperature, and the Rietveld refinement was performed using previously published structural model. 10 Fig. 1a shows the quality of the refinement.…”

“…5,8,9 In this context, we targeted the Co 2+ orthovanadate BaCo 3 (VO 4 ) 2 (OH) 2 because its magnetic properties remain unexplored. 10 Its layered rhombohedral crystal structure ( R 3̄ m space group) is similar but not identical to those of the copper mineral vesignieite BaCu 3 (VO 4 ) 2 (OH) 2 (monoclinic, C 2/ m space group), 11,12 which is a well-known spin-1/2 kagome antiferromagnet, and of the spin-1 nickel compound BaNi 3 (VO 4 ) 2 (OH) 2 (monoclinic, C 2 /m space group), 13 which exhibits a glassy magnetic transition at low temperature. Very small single-crystals of BaCo 3 (VO 4 ) 2 (OH) 2 were already obtained with moderate yield ( ca.…”

“…35%), together with an uninvestigated powder, by hydrothermal reaction. 10 Their crystal structure comprises regular 2D kagome planes of edge-sharing CoO 6 octahedra. However, the size and the quality of these single-crystals did not permit measurements of the physical properties.…”

Microstructured layered-kagome BaCo3(VO4)2(OH)2 with variable crystallite size: alternative synthetic route and comparison with nanostructured samples

“…15,16 All three BaM 3 (VO 4 ) 2 (OH) 2 compounds have similar crystal structures which are built up of M 3 O 6 (OH) 2 brucite-like layers. 12,17,18 These layers are formed from edgesharing MO 4 (OH) 2 octahedra and are kept apart by VO 4 vanadate groups and Ba 2+ ions. Fig.…”

Alkali Transition‐Metal Molybdates: A Stepwise Approach to Geometrically Frustrated Systems

“…The A 2 M 3 (MoO 4 ) 3 (OH) 2 and Cs M 2 (MoO 4 ) 2 (OH) systems represent two new structure types with rare triangular chains for magnetic study. The K M 3 (MoO 4 ) 2 O(OH) system is an interesting modification of the vesignieite (BaCu 3 (VO 4 ) 2 (OH) 2 ) archtype containing vanadate building blocks and well known to exhibit complex magnetic properties and structural subtleties . Molybdates of this type were previously found for the later divalent transition metals as (NH 4 )H M 2 (MoO 4 ) 2 (OH) 2 ( M =Co‐Zn), but in these cases, the transition‐metal site is 2/3 occupied .…”