Precession Electron Diffraction Studies of $Sr_x Ba_{1-x} Nb_2 O_6$ and $Ca_x Ba_{1-x} Nb_2 O_6$ Single Crystals

Crystal structures of two single crystals $Sr_x Ba_{1-x} Nb_2 O_6$ and $Ca_x Ba_{1-x} Nb_2 O_6$ have been reinvestigated using automated electron diffraction tomography method with beam precession. 3D reciprocal space has been reconstructed based on recorded tilt series. For both samples the crystal structure was refined and the tetragonal symmetry with space group P4bm was confirmed. The three dimensional reciprocal space allowed to observe and to study satellite reflections in both materials.