Effect of NiO substitution on the structural and dielectric behaviour of NaNbO3

• Main Authors: Tiwari, Nidhi, George, R. T., Joshi, D. C., Nayak, S., Chauhan, R. N., Pramanik, P., Dar, T. A., Ghosh, S., Thota, S.
• Other Authors: Energy Research Institute @NTU
• Format: Article
• Language: English
• Published: 2019
• Subjects: Ceramics; Antiferroelectricity; DRNTU::Science::Chemistry
• Online Access: https://hdl.handle.net/10356/105833; http://hdl.handle.net/10220/48778
• Institution: Nanyang Technological University

The structural and dielectric properties of NiO substituted NaNbO3 ceramics are reported. The orthorhombic (Pmna) crystal structure of NaNbO3 transforms to a lower symmetry monoclinic phase (Pbma) after the dilute dispersion of NiO. X-ray photoelectron spectroscopy reveals pentavalent “Nb,” monovalent “Na,” and divalent “Ni” states along with the signatures of non-local screening effects. The antiferroelectric to paraelectric transition (TAFE) accompanied by a structural change from the orthorhombic to the tetragonal phase shifts by 55 C toward the low-temperature side, whereas the morphotropic phase boundary (TO-M) moves toward a higher temperature by 28 C for nominal substitutions (x 0:10). The generalized Lyddane-Sachs-Teller expression e0 S0e1 ¼ ðxlxtÞ2 and thermodynamic free energy models are employed to explain the anomalous behaviour of the temperature dependence of relative dielectric permittivity (er(T)) across TAFE and TO-M. The frequency dependence of ac-conductivity rac(x) follows the Jonscher power law (rac ¼ r(0) þ Axs), suggesting the dominance of the phonon-assisted hopping mechanism, whereas the frequency independent term (r(0)) was explained by Funke’s Jump-Relaxation Model.