Preparation of micrometer-sized α-Al2O3 platelets by thermal decomposition of AACH

Micrometer-sized α-Al2O3 platelets with hexagonal shape were prepared by thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) using AlF3 as an additive. The precursor and the calcined product were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. The α-Al2O3 platelets with the size of 2–3 μm were obtained by calcining AACH at 1200 °C with 5 wt.% AlF3. The morphology modification is attributed to the various growth rates along different crystal orientations due to the adsorption and uneven distribution of AlF3. A step growth mode is responsible for the formation of the platelets.

Regular micrometer-sized α-Al2O3 platelets with hexagonal shape were synthesized by thermal decomposition of ammonium aluminum carbonate hydroxide using AlF3 as an additive. The addition of AlF3 to the precursor can change the growth rate of Al2O3 in different directions due to the introduction of Al3+ vacancy and to the formation of AlOF, resulting in the morphology modification of the calcined product. The formation of the α-Al2O3 platelets conforms to a step growth mode along the [0001] crystal orientation.