Synthesis of CoMgAl2O4 Ceramics by Plasma Melting

The paper presents results of an experimental study on the fabrication of ceramics based on MgAl2O4 spinel with the addition of cobalt oxide (Co3O4) at various concentrations of 0.1, 0.25, 0.75, and 1 wt % in a thermal plasma medium. Ceramic samples were synthesized from natural materials with high Al2O3 and MgO oxide contents. It has been found that at lower firing temperatures (1400°C), the addition of Co3O4 more effectively increases density. At higher firing temperatures (1500–1550°C), density initially decreases and then increases with increasing Co3O4 content, a behavior that is associated with phase transitions or changes in the material’s texture. The CIE 1931 chromaticity diagrams characterize the effect of firing temperature and Co3O4 concentration on color change of the ceramics. As can be seen, the points on the diagram shift from the blue range with increasing sintering temperature. It is worth noting that the maximum saturated color on the diagram corresponds to the “melting products.” The optimal Co content in MgAl2O4 spinel is 0.75 wt %; a heterogeneous nanostructure combining the properties of the matrix spinel and Co-containing phases is formed at this concentration.