A neutron powder investigation of the high-temperature structure and phase transition in LiNbO3

The structure of LiNbO 3 has been determined around the phase transition at T c ≃1430 K by neutron powder diffraction using a mirror furnace in air up to 1505 K. The transition is of the order-disorder type with some displacive components. In the paraelectric high-temperature phase, Li is randomly distributed over two sites on both sides of the O plane and Nb assumes a centrosyminetric position within its O 6 octahedron. There are indications of more complicated disorder and a high mobility of Li