Influences of precursor and additive on the morphology of nanocrystalline α-alumina Original Research Article

The temperature for complete transformation to α-Al2O3 changed with precursor and the transformation temperature is lower in the case of using aluminum nitrate precursor as compared to aluminum sulfate precursor. The size of alumina particles obtained using aluminum nitrate precursor was smaller than that obtained using aluminum sulfate precursor, and this may be related to the ability of precursor anion to provide colloid stability. The particles obtained from aluminum nitrate precursor have elongated shape, while those obtained from aluminum sulfate precursor have spherical shape, and it could be attributed to the different characteristics of precipitate formed in the initial stage of reaction. The addition of AlF3 results in decrease of the phase transition temperature to α-alumina. The effect of AlF3 additive on modification of morphology of particles is different depending on the precursor. The change of morphology of α-alumina particles to the plate-like shape was observed in the case of using aluminum nitrate precursor, but not in the case of using aluminum sulfate precursor.