Polycrystalline aluminum substituted barium hexaferrite BaFe11AlO19 synthesized by the ceramic technique. The results of energy dispersive X-ray analysis, thermal X-ray diffraction (XRD), neutron diffraction, Mössbauer spectroscopy, magnet properties measurements were measured. XRD analysis demonstrated P63/mmc hexagonal structure of BaFe11AlO19. The magnetic sublattice of barium hexaferrite BaFe11AlO19 was obtained using neutron diffraction data. The distribution of aluminum in barium hexaferrite matrix at positions 2a and 12k was obtained with Mössbauer spectroscopy. A comparison of the calculated intensities of the neutronograms and the actual ones allowed us to establish that in position 2a the aluminum ion occupied a position with the coordinate (1;1;0), and the position of the substituent ion in position 12k (0.83333; 0.66667; 0.10810). According to neutron diffraction data, it was found that the actual Curie temperature is lower than that measured by differential scanning calorimetry.