Sintering mechanism and properties of corundum-mullite duplex ceramic with MnO2 addition

Corundum-mullite duplex ceramic (CMC) is excellent engineering material that can be strengthened by the addition of various compounds. In this study, the sintering mechanisms of CMC with two nAl2O3: mSiO2 stoichiometric ratios (n = 1, m = 0; n = 3, m = 2) were investigated with different amounts of MnO2 addition. The phase transition, microstructure, distribution of elements and ionic valence of the ceramics were identified via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), respectively. The results show that Al3+ ions in the corundum lattice are replaced by Mn2+ ions. The distorted crystal structure could promote the sintering reaction and leads to a lower sintering temperature. Hence, this study provides beneficial guidance for the industrial production of CMC at lower temperatures and, therefore, with lower energy consumption.