Synthesis and characterization of the manganese cobaltite spinel prepared using two "soft chemical" methods

Using the coprecipitation method and EDTA gel processes, manganese cobaltite (Mn1.5Co1.5O4) powders were successfully synthesized. The thermal decomposition behavior of the gel precursors, phase formation and morphology of the Mn1.5Co1.5O4 powders were characterized by means of DTA/TGA and MS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Well-crystallized dual-phase manganese cobaltite spinel, containing both the cubic and tetragonal phases, was obtained at room temperature for both types of powders calcinated at 800 °C for 10 h in static air, without formation of any intermediate phase. SEM investigations show that the Mn1.5Co1.5O4 powders prepared using two "soft chemical" methods were agglomerates composed of approximately micron-sized particles. The structure and morphology of the bulk samples, as well as their electrical conductivity, were investigated using XRD, SEM, and EIS, respectively. Mn1.5Co1.5O4 spinels with different microstructure exhibited excellent electrical conductivity and structural stability. Major emphasis was placed on structural transformations of the spinel solid solutions with temperature and their effect on the electrical properties of these solutions. -- Highlights: ► Mn1.5Co1.5O4 powders were prepared using coprecipitation and EDTA gel processes. ► Approximately micron-sized particles with cubic and tetragonal grains. ► A transition occurs in the 250–450 °C range. ► Only the cubic spinel phase is observed at higher temperatures. ► At higher temperature electrical conductivity is related to the grain volume.