Microstructured layered-kagome BaCo 3 (VO 4 ) 2 (OH) 2 with variable crystallite size: alternative synthetic route and comparison with nanostructured samples.

Microplatelets of the layered-kagome compound BaCo(VO)(OH), which is the Co analogue of mineral vesignieite BaCu(VO)(OH), have been prepared with very high yield by hydrothermal reaction using synthetic karpenkoite CoVO(OH)·2HO as starting reagent. The Rietveld refinement of X-ray diffraction data indicates that CoVO(OH)·2HO is isostructural with martyite ZnVO(OH)·2HO. Two single-phased samples of microstructured BaCo(VO)(OH) 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 -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 BaCo(VO)(OH). This study highlights that the magnetic properties depend on the crystallite sizes only at low temperatures.