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 3 (VO 4 ) 2 (OH) 2 , which is the Co 2+ analogue of mineral vesignieite BaCu 3 (VO 4 ) 2 (OH) 2 , have been prepared with very high yield by hydrothermal reaction using synthetic karpenkoite Co 3 V 2 O 7 (OH) 2 ·2H 2 O as starting reagent. The Rietveld refinement of X-ray diffraction data indicates that Co 3 V 2 O 7 (OH) 2 ·2H 2 O is isostructural with martyite Zn 3 V 2 O 7 (OH) 2 ·2H 2 O. Two single-phased samples of microstructured BaCo 3 (VO 4 ) 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 BaCo 3 (VO 4 ) 2 (OH) 2 . This study highlights that the magnetic properties depend on the crystallite sizes only at low temperatures.