Ti4+ addition effect on α-Al2O3 flakes synthesis using a mixture of boehmite and potassium sulfate

Single-crystal α-Al2O3 hexagonal flakes with a diameter of about 200 nm and 20 nm in thickness were obtained by mixing different molar ratios of potassium sulfate to boehmite and heating at 1000 °C. Co-doping 1 mol% TiO2 can increase the shape anisotropy of α-Al2O3 hexagonal flakes, increasing the diameter to 400 nm. The effects of potassium sulfate, Fe2O3 and TiO2 on the phase transformation and morphology development of alumina were investigated using X-ray diffraction analysis (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The results indicate that co-doping potassium sulfate, Fe3+ and Ti4+ can promote γ → α-Al2O3 phase transformation and change the morphology from a vermicular structure into hexagonal platelets. The shape anisotropy of α-Al2O3 hexagonal flakes can be increased by adding TiO2 due to the segregation of Ti4+ ions onto the surfaces of basal planes of α-Al2O3 single crystal particle.