Crystal structures of Na{sub 1/2}Ln{sub 1/2}TiO{sub 3} (Ln: La, Eu, Tb)

Neutron powder diffraction studies of Na{sub 1/2}La{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3}, and a synchrotron X-ray powder diffraction study of Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} have been carried out. Rietveld refinement of the structures confirmed that Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3} crystallizes in GdFeO{sub 3} type of structure (space group Pbnm). The ambiguity in the literature regarding the crystal structure of Na{sub 1/2}La{sub 1/2}TiO{sub 3} has been resolved and the correct space group is found to be R3-bar c. A detailed list of refined structural parameters of these compounds is presented for the first time.