| Up to now, the oxidation behavior of MgAlON has been investigated based on MgAlON prepared from high purity raw materials without considering the effects of impurities. In this work, the effects of impurity kinds and contents on the lattice constant of MgAlON were studied. The relation between oxidation behavior of MgAlON and impurities kinds and contents was explored.In this work, the dependence of the crystal lattice constant of MgAlON powders on different impurities was examined. The single-phase MgAlON was synthesized by reduction-nitridation techniques at 1550℃for 5 hours using Al2O3, MgO and Al powders as main raw materials, and Fe2O3, SiO2 and TiO2 as additives. The results show that the lattice constant of MgAlON without impurities was 0.80185nm. The lattice constants of MgAlON with 6% F2O3,5% SiO2 and 5% TiO2 were 0.79917nm, 0.79915nm and 0.79977nm respectively. The addition of impurities slightly reduced crystal lattice constant of MgAlON. Together with the results of XRD, EDS and XPS, it is confirmed that the additives Fe2O3, SiO2 and TiO2 entered into MgAlON crystal lattice as solid solution.The effects of impurities on the oxidation behavior of MgAlON were investigated emphatically. The results exhibited that the starting oxidation temperatures of MgAlON were reduced in different degree by adding different types of impurities (Fe2O3, SiO2and TiO2). The effects of impurities contents (Fe2O3:2%, 4%,6%; SiO2:3%,5%,7%; TiO2:1%,3%,5%) on the starting oxidation temperatures of MgAlON was not significant. The starting oxidation temperatures of the samples with varying SiO2 amounts were all 900℃, the same as the sample without impurities. The samples with Fe2O3 and SiO2 started to be oxidized at 850℃, 50℃lower than the sample without impurities.The temperatures at which Al2O3 started to form in the oxidation process of MgAlON were reduced equally by adding different types of impurities (Fe2O3, SiO2 and TiO2). The alumina precipitation temperatures of the samples with impurities were all 1200℃, lower than that of the sample without impurities by 200℃. The alumina formation temperatures of MgAlON with higher contents of TiO2 (3%,5%) were reduced by 300℃. The other changes in impurity contents did not produce significant effect on the alumina formation temperatures of MgAlON.Different types of impurities had significantly different effects on the complete oxidation temperature of MgAlON. The complete oxidation temperature of the sample without impurities was 1500℃. The samples containing Fe2O3 and SiO2 were oxidated completely at 1400℃, which was lower than that of the sample without imputies by 100℃. The samples with TiO2 were completely oxidized at 1300℃, which was lower than that of the sample without impuritis by 200℃. The quantity changes of added SiO2 and TiO2 did not show significant effects on the complete oxidation temperatures of MgAlON. The complete oxidation temperature of sample with 2% Fe2O3 was the same as that of the sample without impurities. The complete oxidation temperatures of MgAlON with higher quantities of Fe2O3 (4%,6%) were reduced by 100℃.Impurities exhibited varying effects on the changes of lattice constant of MgAlON in the oxidation process. In the oxidation process of the samples with SiO2 and TiO2, the positions of MgAlON diffraction peaks were shifted to high angle at lower temperatures and then to the low angle at higher temperatures. The lattice constant decreased with temperatures in the lower temperature region due to the reduction of nitrogen content, and increased gradually because the crystal structure was converted from MgAlON to MgAl2O4. The lattice constant of the samples with Fe2O3 increased with the temperature in the oxidation process, possibly due to dissolving of FeO/Fe2O3 into the MgAlON crystal lattice.The results of this work have some enlightening significance on the selection of natural raw materials for synthesis of MgAlON. That is, when considering natural raw materials to prepare MgAlON material, those with lower contents of Fe2O3, SiO2 and TiO2, particularly lower content of TiO2, should be selected in order to avoid the deterioration of the antioxidizing property of MgAlON due to the presence of impurities.
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