Evidence of Wolframite-Type Structure in Ultrasmall Nanocrystals with a Targeted Composition MnWO4
Pascaline Patureau1, Rémi Dessapt1, Pierre-Emmanuel Petit1
1Institut des Matériaux Jean Rouxel (IMN) , Université de Nantes, CNRS , 2 rue de la Houssinière , BP 32229, 44322 Nantes cedex 3, France.
Abstract:
Here, we report a study of white-ochre powders with targeted composition MnWO4 prepared via a coprecipitation method. Through X-ray total scattering combined with pair distribution function analysis and Rietveld refinement of X-ray diffraction data, we find that their crystal structure is similar to that of bulk-MnWO4, despite a mean crystallite size of 1.0-1.6 nm and a significant deviation of the average chemical composition from MnWO4. The chemical formula derived from elemental and thermogravimetric analyses is Mn0.8WO3.6(OH)0.4·3H2O. X-ray absorption and magnetic susceptibility measurements show that Mn and W have the same oxidation states as in MnWO4. No magnetic ordering or spin glass or superparamagnetic behavior is observed above 2 K, unlike in the case of MnWO4 nanocrystals having a mean size higher than 10 nm.
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