Preparation and Crystal Structure Refinement of Li 4Mn 5O 12 by the Rietveld Method

Well-crystallized Li 4Mn 5O 12 powder has been prepared by heating a eutectic mixture of lithium acetate LiOAc and manganese nitrate Mn(NO 3) 2 at 700°C for 1-3 days in an O 2 atmosphere. The Li and Mn content in the final products was determined from atomic absorption spectroscopy. The tetravalent manganese in the final product was found to be 95% based on the active oxygen content determined by KMnO 4 titration. The structure of Li 4Mn 5O 12 crystallites was refined by the Rietveld method from powder X-ray diffraction data as a cubic spinel, a = 8.1616(5) Å, space group Fd3̄ m . Li 4Mn 5O 12 crystallites are stable at temperatures up to 600°C in oxygen but decompose to spinel LiMn 2O 4 and monoclinic Li 2MnO 3 at temperatures higher than 530°C in N 2.