Crystal structure of the electric-fieldinduced ferroelectric phase of NaNbO3

The structure of electric-field-induced ferroelectric phase of NaNbO3 has been studied by means of X-ray diffraction method. Crystal cell is orthorhombic (P21 ma) with parameters: a = 5.569. b = 7.790, c = 5.518 Å, V = 239.38 Å3, Z = 4. Field-induced phase transition mainly results in reversal of atomic shift directions relative to the cubic perovskite atomic positions in one half of initial orthorhombic cell. Increasing of NbO6 octahedra tilts and additional displacements of some oxygen atoms are accounted for electric field effect.