We present results obtained from a combination of dielectric and x-ray diffraction measurements for compositional design of (1-x) NaNbO₃-xBaTiO₃ (NNBTx), which can induce interferroelectric phase transitions. Anomalies are observed in dielectric measurements performed for various compositions at 300 K, as well as at different temperatures for NNBT03. We observed the appearance(disappearance) of the superlattice reflections along with change in the intensities of the main perovskite peaks in the powder x-ray diffraction data, which provide clear evidences for structural phase transitions with composition and temperature.We found that increasing the concentration of BaTiO₃ leads to the suppression of out-of-phase rotation of octahedra and an increment in tetragonality (c / a ratio), which promotes the polar mode at room temperature. The temperature-dependent powder diffraction study shows that the ferroelectric rhombohedral phase of pure sodium niobate gets suppressed for the composition x = 0.03, and the monoclinic phase Cc gets stabilized at low temperature. The monoclinic phase is believed to provide for a flexible polarization rotation and is considered to be directly linked to the high-performance piezoelectricity in materials due to presence of more easy axes for spontaneous polarizations than the rhombohedral phase.