X-ray powder diffraction data for κ-Al2O3 are reported. It was concluded that κ-Al2O3 belongs to the orthorhombic crystal system with space group Pna21. The lattice parameters were found to be a=4.8351(3) Å, b=8.3109(5) Å, c=8.9363(3) Å. There are 16 Al3+ and 24 O2− in the unit cell, and thus the number of chemical formulas in the unit cell, Z, is 8. The volume V of the unit cell is equal to 359.09(6) Å3 and the theoretical density Dx is 3.772 g/cm3. The Smith–Snyder (F20) and the de Wolff (M20) values for these data are 136.1 (0.0059, 25) and 98.4, respectively.
