Dielectric/impedance spectroscopy describes the electrical properties of a medium as a function of frequency in the range of 10^−5 to 10^12 Hz. This is a powerful advanced physical tool and technique to characterize electrical properties of materials in the field of material science, super-cooled materials, colloidal science, polymer science, pharmaceutical sciences, composites, nanomaterials, soft condensed matter, etc.
My presentation will focus on dielectric/impedance spectroscopy for ion-conducting solids and super-cooled liquids and provide a considerable new physical insight into the nature of the ionic motion and dipolar motion. Interpreting and extracting the physical insight from the dielectric/impedance spectroscopy data has been a matter of considerable debate, for details consult the references in [1-3]. Particularly, in regards to how best to represent the relaxation process that is the result of transition from correlated to uncorrelated ion hopping in ionic solids and dipolar orientation motion in super-cooled liquids and other dielectrics. Although interpretations based upon the complex impedance and complex electric modulus have featured prominently in the earlier literature, direct analysis of the complex conductivity in the frequency domain is gaining acceptance as it provides direct information regarding the microscopic mean-squared displacement of ions in ion conducting solids. In the case of low loss dielectrics and super-cooled liquids, the intrinsic dipolar orientation motion in the interpretation have featured in the complex dielectric.
Many of our recent findings are summarized emphasising the complex conductivity, the complex dielectric and their combination present in the dielectric/conductivity spectra and demonstrated how a researcher have to interpret dielectric/impedance spectroscopy data with elaborate data analysis [1]. Further, a renewed non-Debye relaxation processes is proposed [2, 3] recently. It is unique model incorporating the fundamental laws of physics, namely, the conservation of charge, moment and energy [2, 3]. My talk will focus on (i) Debye relaxation law and its deviation non-Debye relaxation (ii) Observation of ion motion and dipolar motion by conductivity and dielectric spectroscopy (iii) Combination of hopping conduction motion and dielectric dipole motion [1,4-6] (iv) Spectroscopy data representation and understanding of ion and dipole motion (v) Unique non-Debye relaxation and new physical insights [1-3].
References
1. Analysis of conductivity and dielectric spectra of Mn0.5Zn0.5Fe2O4 with coupled Cole-Cole type anomalous relaxations, N.S.K. Kumar, T.S. Shahid, G. Govindaraj, Physica B: Condensed Matter, 488, 99–107 (2016).
2. Unique non-Debye relaxation process and new physical insight for the dielectric loss, G. Govindaraj, Society for Materials Chemistry Bulletin, 8, 41-51 (2017).
http://smcindia.org/pdf/SMC%20Bulletin%20April%202017.pdf
3. Unique dielectric dipole and hopping ion dipole relaxation in disordered systems, G. Govindaraj, AIP Conference Proceedings 1951, 020016 (2018); doi: 10.1063/1.5031724.
4. Conduction and dielectric relaxations in PVA/PVP hydrogel synthesized cerium oxide, P. M. Junais and G Govindaraj, Mater. Res. Express 6, 045914 (13) (2019).
5. Nanocrystalline Li2MoO4: Synthesis and electrical studies, Rajesh Cheruku, D. Surya Bhaskaram, G. Govindaraj, Lakshmi Vijayan, Journal of Alloys and Compounds, 788, 779-786 (2019).
6. Unusual combination of conduction and dielectric relaxations in nanocrystalline -Fe2O3, P. M. Junais, G. Govindaraj, Materials Letters, 264, 127314-16 (2020).
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