Giant dielectric response and polaronic hopping in Al-substituted A5/3Sr1/3NiO4 (A=La, Nd) ceramics

The structures and dielectric properties of A5/3Sr1/3Ni1−xAlxO4 (A=La, Nd; x=0.2, 0.3) ceramics were investigated. The single tetragonal phases were found in all ceramics. Giant dielectric responses were observed in these ceramics, and only one dielectric relaxation was found on the curve of the temperature dependence of dielectric constant. 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 in these ceramics.