Synthesis and thermal evolution of Mn-doped alumina nanoparticles by homogeneous precipitation with urea

This work describes the synthesis of nanoparticles of Mn-doped alumina from hydrolysis of manganese and aluminium salts at 60 °C in the presence of urea. The thermal evolution of the particles obtained by this method from the poor crystalline initial hydrous oxide up to a sintering temperature of over 1500 °C has been studied as well as the changes in morphology and crystallinity of the powder for all the intermediate temperatures. The results indicate that this synthesis process gives very small and highly dispersed particles of about 2 nm that transform to metastable phases of alumina as the temperature increases. The sintered sample shows a biphasic and homogeneous microstructure formed by alumina equiaxed grains and polygonal MnAl2O4.