Dielectric Properties of Strontium Titanate Solid Solutions Containing Niobia

SrTiO ₃ solid solutions containing Sr _0.5 NbO ₃ were studied by X‐ray diffraction and dielectric measurements. Single‐phase perovskite solid solutions were formed up to the composition containing 30 mole % Sr _0.5 NbO ₃ . The addition of niobium resulted in a symmetry change from cubic (SrTiO ₃ ) to tetragonal (solid solution) and the c/a ratio increased with increasing niobium content. The dielectric constant for the solid solutions was lower than that for SrTiO ₃ . Pronounced dielectric relaxation peaks and dispersion in permittivity were observed for the composition 7SrTiO ₃ :3Sr _0.5 NbO ₃ . The activation energy for the relaxation process is about 0.42 ev. It is suggested that the existence of the A‐site vacancy in the perovskite ABO ₃ lattice introduced by the niobium substitution distorts the oxygen octahedra, producing more than one possible “noncentral” site for the Ti ⁴⁺ ion. The relaxation arises from the thermal motion over potential barriers separating these alternative sites.