Enhancement of the dielectric response through Al-substitution in La1.6Sr0.4NiO4 nickelates

Abstract

The structures and dielectric properties of La_1.6Sr_0.4Ni_1−xAl_xO₄ (x = 0, 0.2 and 0.4) ceramics elaborated using the Pechini method were studied for the first time. The same unique tetragonal phase was found in all compounds. The lattice parameters were found using Rietveld refinement. The surface morphology characterization and elemental analysis of these samples were respectively carried out using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A giant dielectric response was observed in these ceramics, and one dielectric relaxation was found. The substitution of nickel with aluminum results in a colossal dielectric constant value (>10⁶). The dielectric loss also drops with the increasing Al content; for x = 0.4 it is divided by 100 at room temperature for low frequencies. The giant dielectric response and low-temperature relaxation were mainly attributed to thermally activated small polaronic hopping in these compounds.