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

Abstract

Microplatelets of the layered-kagome compound BaCo₃(VO₄)₂(OH)₂, which is the Co²⁺ analogue of mineral vesignieite BaCu₃(VO₄)₂(OH)₂, have been prepared with very high yield by hydrothermal reaction using synthetic karpenkoite Co₃V₂O₇(OH)₂·2H₂O as starting reagent. The Rietveld refinement of X-ray diffraction data indicates that Co₃V₂O₇(OH)₂·2H₂O is isostructural with martyite Zn₃V₂O₇(OH)₂·2H₂O. Two single-phased samples of microstructured BaCo₃(VO₄)₂(OH)₂ have been characterized using powder X-ray diffraction, FT-IR and Raman spectroscopies, thermal analyses, scanning electron microscopy, energy-dispersive X-ray spectroscopy and magnetisation measurements. Their crystallite sizes perpendicular to the c-axis are in the range of 92(3) to 146(6) nm and depend on the synthesis conditions. Results have been compared to those previously obtained for quasi-spherical nanoparticles having a crystallite size of the order of 20 nm, to explore the effect of the crystallite size on the properties of BaCo₃(VO₄)₂(OH)₂. This study highlights that the magnetic properties depend on the crystallite sizes only at low temperatures.