Pure and undoped strontium-barium niobate Sr0.72Ba0.25Nb2O5.97 single crystals grown by the Czo-chralski method were investigated. Using X-ray Bond's method lattice parameters of this crystals are determined with high accuracy in the order of Delta d/d = 10(-5), Based On the lattice parameter data measured at 298 K it was ascertained that the Sr0.72Ba0.25Nb2O5.97 single crystals belong to the tetragonal system. The additional analysis of the diffraction patterns performed by the Lane method confirmed the occurrence of a four-fold axis of symmetry. (C) 2013 Elsevier B.V. All rights reserved.