Electron microscopy and structural studies of Nd1/3NbO3

Abstract The crystal structure of the deficient perovskite Nd 1/3 NbO 3 has been determined at room temperature, using electron microscopy observations and X-ray powder diffraction data. Electron diffraction study and HRTEM images evidence the doubling of a and b parameters and confirm one of the c -parameter with respect to perovskite unit cell. The structure refinement has been carried out using the orthorhombic Cmmm space group. The Nd 3+ cations occupy randomly and alternatively the (00l) planes and Nb 5+ cations distorted octahedral sites. This structure is characterized by the presence of empty Nd 3+ sites in every second layer and the tilting of the octahedral sites around the b -axis. In addition, electron diffraction patterns exhibit weak additional diffuse reflections, which supposes some ordering of the Nd vacancies.