Abstract
Mn-substituted cordierites, 2(Mg1−xMnx)O·2Al2O3·5SiO2 (x = 0–1), were prepared from natural components (talc, clay, alumina) and MnO2. Sintering behavior, phase transformation, and microstructural features of the samples were investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), dilatometric measurements and scanning electron microscopy (SEM) with energy dispersive analysis (EDS). The results of DTA and XRD analysis indicate that MnO2 is successively reduced to Mn2O3 and MnO in the sintering process. Mn2+ ions incorporate into the crystal structure of α-cordierite substituting Mg2+ ions in octahedral sites and thus increasing the cordierite unit cell volume. Mn promotes the sintering process: the crystallization temperature, melting point, density and open porosity of Mn-substituted cordierites lowered, whereas the shrinkage and medium pore diameter enlarged with an increase in MnO2 content in the mixture of raw materials. Surface enrichment with Mn with the formation of manganese oxide crystallites was found for the samples with high substitution degree.
Published Version
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