X-ray, optical and dielectric studies of diffused phase transitions in NaNbO3-based solid solution crystals by Raevskaya, S, Semenchev, A, Abdulvakhidov, K, Raevski, I, Prosandeev, SA, Shilkina, L, Smotrakov, V, Eremkin, V, Shuvaeva, V, Glazer, A