Dielectric relaxation and polaronic hopping in Al-substituted Sm_1.5Sr_0.5NiO₄ ceramics

Abstract

The structure and dielectric properties of Sm 1.5 Sr 0.5 Ni 1− x Al x O 4 ( x = 0.3, 0.5) ceramics were presented. A single orthorhombic phase was obtained in Sm 1.5 Sr 0.5 Ni 0.7 Al 0.3 O 4 ceramics, while minor impurities existed in Sm 1.5 Sr 0.5 Ni 0.5 Al 0.5 O 4 ceramics. Temperature stable giant dielectric response was observed in these two ceramics, and only one dielectric relaxation was found. After comparing the activation energies of dielectric relaxation and electrical conduction, the giant dielectric response should be attributed to the adiabatic small polaronic hopping process, and the dielectric behaviour of the samples with different aluminium contents confirmed the correlation between the dielectric response and electrical conduction.