Giant dielectric response in (Sm1−xNdx)1.5Sr0.5NiO4 ceramics: The intrinsic and extrinsic effects

Abstract

(Sm1−xNdx)1.5Sr0.5NiO4 solid solution ceramics with K2NiF4-type structure have been synthesized in the entire range of 0.2 ≤ x ≤ 0.8. All compositions can form the single orthorhombic phase in a space group of Bmab (64). With increasing x, the crystal structure has a tendency of transforming from orthorhombic to tetragonal phase, and this transformation should be related to the average radius of ions in K-site. The relationships between the low temperature dielectric relaxations and the adiabatic small polaronic hopping processes in all compositions are confirmed. Because of the inhomogeneity and fluctuation of the constituent and structure, the dielectric relaxations above room temperature are originated from extrinsic Maxwell-Wagner effect in the compositions with x = 0.4, and 0.6. The low-frequency dielectric relaxation observed in the sample of x = 0.8 is attributed to grain boundary effect.