Structural aspects and ionic conductivity in perovskite-like doped niobates and titanates

Aliovalent substitution in the cation sublattices of perovskite-like niobates of the type (Pb_1−xLa_2/3x−yLi_3x)Nb₂O₆ were studied. Their crystallographic peculiarities and electrophysical properties were investigated. It has been found that at x=1 lanthanum-lithium niobates with the structure of the defect La_2/3−yLi_3yNb₂O₃ perovskite are formed, which possess a high lithium-ion conductivity. The symmetry of the perovskite crystal lattice is shown to become higher and to change from rhombic to tetragonal and cubic with increasing lithium content. The La_2/3-xLiTiO₃ compounds have a perovskite structure and a high lithium ion conductivity. The Lines model for superionic conductor gives a satisfactory fit to the frequency-temperature nature of the electrophysical properties.