1. TEM observations of a grain surface of 0.1wt% AlF₃ doped sample (a) Original surface before high magnification observation; (b) Surface after high magnification observation, where sphere precipitates separated out; (c-d) Black arrow shows the growing of a new precipitate under irradiation; (e) Lattice fringes of a precipitated crystal

2. EELS of the precipitation and its reference

3. HRTEM images and selected area diffraction of AlF₃ doped alumina grain (a) HRTEM images of AlF₃ doped alumina grain before Al precipitation. White arrows points to the planer defects; (b) The same grain after Al precipitation; (c, d) Diffraction patterns correspond to the grain before and after Al precipitation, respectively. The zone axis is along [0001] direction; (e) Magnification of area i in (a). The dotted box traces a dislocation core and the parallel lines show the distortion contrast composed of three or four layers; (f) Inversed FFT of the area ii in (a) from (21¯1¯0)/(2¯110) diffraction spots

4. (a) Schematic diagram of cation sub-lattice in α-alumina. The open and closed circles are the unoccupied and occupied octahedron sites respectively. Half-filled circles represent octahedron sites occupied by extrinsic Al³⁺ ions; (b) Real alumina structure in [112¯0] projection. The red box selects an Al layer between two oxygen layers; (c, d) Structures of the selected Al ions layer repainted in [0001] projection, before and after the act of a 1/3 [11¯00] partial dislocation, respectively. The open circles indicate unoccupied octahedron sites in the same layer