Dielectric relaxation and polaronic hopping in Mn-substituted LaSrNiO4 nickelates prepared by mechanical milling method

• Published in: Journal of alloys and compounds Vol. 688; pp. 163 - 172
• Main Authors: Chouket, A., Optasanu, V., Bidault, O., Cheikhrouhou, A., Cheikhrouhou-Koubaa, W., Khitouni, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2016; Elsevier
• Subjects: Dielectric measurements; Engineering Sciences; Equivalent circuit; K2NiF4-type structure; Materials; Mechanical milling method; Rietveld refinement; Mechanical milling method; Rietveld refinement; K2NiF4-type structure; Dielectric measurements; Equivalent circuit
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.06.288

The structures, microstructures and dielectric properties of LaSrNi1−xMnxO4 (x = 0, 0.1, 0.2, 0.3 and 0.5) ceramics synthetized by mechanical milling followed by heat treatment were studied. One single tetragonal phase was revealed in all compounds. Structural parameters were obtained by Rietveld refinement. The substitution of Ni ions by Mn produces a variation of the lattice parameters but no phase change is observed. The surface morphology and elemental analysis of these samples were respectively investigated by Scanning Electron Microscopy (SEM) and energy dispersive X-ray technique (EDS). Giant dielectric response was observed in these ceramics, and at least two relaxations were found on the curve of the temperature dependence of dielectric constant. An equivalent circuit [R-C][R-CPE] was used to fit the experimental data and provide the activation energy of the thermally activated relaxation. The activation energy values confirm the thermally activated small polaronic hopping contribution to the giant dielectric response. •Monophasic structure obtained by high-energy ball milling process/high temperature sintering.•Giant dielectric constants (∼105) at room temperature and low dielectric loss (∼1) were measured.•High-frequency dielectric relaxation attributed to the adiabatic small polaron hopping process.•The substitution of Ni by Mn brings an enhancement in terms of dielectric loss.