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MACIEL, A. P.; LEITE, E. R.; LONGO, E. and VARELA, J. A.. Sol-gel modified method for obtaining a-alumina nanocoated with rare earth. Cerâmica [online]. 2005, vol.51, n.317, pp.52-57. ISSN 0366-6913. http://dx.doi.org/10.1590/S0366-69132005000100010.
a-alumina powder was nanocoated with lanthanum oxide by sol-gel like method. A lanthanum polymeric precursor was used to coat the a-Al2O3 dispersed in water. The influence of the lanthanum oxide nanocoating on the sintering and microstructure of a-alumina was investigated using electron microscopy techniques. Scanning electron microscopy (SEM) of these nanocoated grains revealed that the lanthanum oxide precipitates on the grain boundary of the a-alumina, at high temperature. High-resolution electron microscopy (HREM) observations clearly showed the formation of a La2O3 layer on the surface of the a-alumina. The La2O3 layer modified the sintering process of the pure alumina. At high temperatures significant modifications on the grain morphology and microstructure was observed. It was verified that an amorphous La2O3 layer reacts with the a-alumina grain, resulting in LaAlO3 and increasing the sintering temperature. The La2Al24,4O39,6 phase was observed.
Keywords : a-Al2O3; nanocoating; rare-earth.