Microstructural analysis of inversion degree in sol-gel synthesized spinel MnCo2O4 particles

Spinel-type compounds exhibit versatile structural and functional properties, which stems from the unique cation distribution that spans a spectrum from partial to total cell inversion degrees. In this study, we investigated the preparation of MnCo¿O¿ particles synthesized via a modified sol-gel method. The synthesized particles were thoroughly characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and Rietveld refinements to assess their microstructural properties. The impact of different annealing temperatures (1000, 1100, and 1200 °C) and durations (1 and 8 h) on the crystal evolution of the synthesized particles was systematically investigated to assess the structural adaptability of the MnCo¿O¿ spinel under these synthesis conditions. The degree of inversion and oxygen positional parameters within the crystalline systems were quantified using the Bertaut method to obtain the specific arrangement of manganese and cobalt ions for inversion degrees from approximately 0.85 (random) to 1.00 (inversion) with the presence of a secondary phase of Co3O4 (20 wt%). The lattice parameter was determined from Rietveld analysis to be 8.2720 and 8.2927 Å for the normal and inverted spinel, respectively. Finally, the I(220)/I(400) and I(400)/I(422) intensity ratios were identified as reliable indicators of inversion degree, with these intensities ratios significantly influenced by the oxygen positional parameter. © 2024 Elsevier B.V.