Synthesis and characterization of a series of cobalt-manganese pyrophosphate CoxMn2-xP2O7 (x=0, 0.25, 0.5, and 1) compounds

Cobalt-manganese pyrophosphate nanostructures with formula CoxMn2 - xP2O7 (x = 0, 0.25, 0.5, and 1) were successfully prepared via two different methods: the precipitation and the hydrothermal at 150 degrees C using poly-ethylene-glycol-5000 (PEG-5000), with further calcinations at 500 degrees C. The Rietveld refinement of the XRD data confirms that CoxMn2 - xP2O7 nanoparticles crystallize in the monoclinic system with space group C2/m. The crystallite size obtained from X-ray line broadening was found to be 41 nm for the Mn2P2O7 compound. The grain size of CoxMn2 (-) xP2O7 varies when increasing the degree of substitution. IR and Raman studies show characteristic bands of the P2O74- anion. A correlation between the partial replacement of Mn by Co and the dependent lattice parameters, the microstructure and the spectroscopic properties was observed. An effort has been made to explain the observed correlation with a qualitative model. (C) 2012 Elsevier B.V. All rights reserved.