THERMAL-BEHAVIOR AND REACTIVITY OF MANGANESE COBALTITES MNXCO3-XO4 (0.0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1.0) OBTAINED AT LOW-TEMPERATURE

The thermal behaviour and reactivity in air, N2 and vacuum of manganese cobaltites MnxCo3-xO4 (0 less-than-or-equal-to x less-than-or-equal-to 1.0) with a cubic spinel-type structure obtained at low temperature have been studied by thermal analysis, X-ray powder diffraction, IR spectroscopy, transmission electron microscopy and X-ray energy-dispersive spectroscopy. In air, the formation of mixed Co-Mn oxides with rock-salt-type structure as a single phase is attained between 1100-1300-degrees-C, depending on x. In a vacuum, the rock-salt-type mixed oxide is formed at ca. 700-degrees-C; Co metal and MnO are the products obtained at 800-degrees-C. The change with temperature of the lattice constant in the cubic spinel-type phase MnCo2O4, has been also determined. It increases from a = 8.167(2) angstrom at 450-degrees-C to 8.2626(3) angstrom at 950-degrees-C. These results are interpreted with regard to the progressive reduction of manganese in the cubic spinel lattice.