Crystal structure of La(Mg2/3Nb1/3)O3 ceramics

The crystal structure of La(Mg2/3Nb1/3)O3 has been analyzed by high-resolution transmission electron microscopy (HRTEM) and Rietveld refinement using X-ray and neutron powder diffraction patterns. According to our analysis, La(Mg2/3Nb1/3)O3 has the 1:1 ordered monoclinic P21/n structure, contrary to the results of previous works which suggest a 1:1 ordered rhombohedral R3̄ or orthorhombic Pbnmstructure. The lattice parameters of La(Mg2/3Nb1/3)O3 are a = 5.6052, b = 5.6482, c = 7.9414 Å, and β = 89.9501°. Monoclinic La(Mg2/3Nb1/3)O3 is distorted by the inphase and the antiphase tilting of octahedra with the a−a−c+ tilting system. The antiparallel shift of A-site cations was also found in La(Mg2/3Nb1/3)O3.