The homometallic warwickite V2OBO3.

Abstract The synthesis, structure and elementary magnetic characterization of the homometallic warwickite V 2 OBO 3 are reported. The material adopts the orthorhombic warwickite structure type at room temperature, space group Pnma (No. 62) with lattice parameters a = 9.2317(1) Å, b = 3.1172(1) Å, and c = 9.5313(1) Å. Temperature-dependent magnetic susceptibility, electrical resistivity, and specific heat measurements show anomalies near 35 K, between 135 K and 150 K, and near 260 K, with the transition at ~ 35 K likely to a ferrimagnetic state. High resolution synchrotron powder X-ray diffraction data at temperatures between 295 K and 90 K display significant peak splitting upon cooling, indicating that at least one crystallographic symmetry change occurs at low temperatures. Graphical abstract Crystal structure of homometallic warwickite V 2 OBO 3 at ambient temperature, viewed down the b -direction (left), looking down on the ribbons made from edge-sharing VO 6 octahedra. The trigonal planar BO 3 groups are also shown. The octahedra share edges in the ribbons (top right). Vanadium is shown in blue (inside the orange octahedra), boron in grey, and oxygen in red. An isolated set of V2-V1-V1-V2 –oxygen octahedra in the width of the ribbon, with all atoms labeled, is also shown (bottom right). fx1 Highlights • New mixed valent vanadium borate. • Multiple phase transitions on cooling. • High resolution synchrotron powder X-ray diffraction data. [ABSTRACT FROM AUTHOR]