[en] The lead free materials with perovskite structure gained great deal of attention because of their wide range of applications. Recently, sodium niobate (NN) and sodium bismuth titanate (NBT) based relaxor antiferroelectric (AFE) ceramics are actively explored for ultra high energy storage applications. However, structure property correlations in this system are not studied in detailed. In this work, the solid solutions of xNa_0.5Bi_0.5TiO₃ (NBT)-(1-x)NaNbO₃(NN) for 0<x<1 were prepared using solid state reaction method and their structure has been characterized at room temperature by X-ray diffraction. We found interesting structural changes with variation of composition. Since the phase transitions in this system are mainly due to the tilt of oxygen octahedra and the displacement of A and B cations, we studied the structure by medium resolution neutron powder diffraction (PD-2 diffractometer) at Dhruva for selected compositions. The knowledge of super lattice reflections and splitting in main perovskite reflections give information about the crystal symmetry. Using group theoretical calculations proposed by stokes, we have modelled and refined the neutron diffraction data to identify the structure at all compositions. Further details of the results will be discussed