Hopping conduction mechanism and impedance spectroscopy analyses of La0.70Sr0.25Na0.05Mn0.70Ti0.30O3 ceramic

The perovskite sample La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 (LSNM0.70T0.30) was produced via a solid-state route process. The frequency dependence of electrical conduction plot established that according to the Jonscher law. The electrical conduction process was based on both theoretical conduction models assigned to the non-overlapping small polaron tunneling model at low temperatures and correlated barrier hopping mechanism at high temperatures. Detailed investigation of impedance data revealed a non-Debye-type relaxation occurring in the polycrystalline. In addition, the dielectric response confirmed the dominance of the Maxwell–Wagner model and Koop’s phenomenological theory effect in conduction phenomenon. The values of permittivity is high for LSNM0.70T0.30 were observed. These values make this composition interesting for microelectric applications. In the thermal study, the relaxation processes observed by electrical conductivity, impedance, and modulus are associated with singly and doubly ionized oxygen vacancies for the lower and higher temperature, respectively. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Majmaah University, MU: R-2021-121The author would like to thank Deanship of Scientific Research at Majmaah University for supporting this work under Project Number No. R-2021-121

Theoretical study of indigotine blue dye adsorption on CoFe2O4/chitosan magnetic composite via analytical model

An advanced model is applied to analytically explore the adsorption mechanism of Indigotine blue dye (IBD) onto a CoFe2O4/chitosan magnetic composite (CoFe2O4/CMC). Contrary to the classical adsorption models, the model is defined starting from the statistical physics theory and it is a generalized model containing numerous parameters having a defined physical meaning. Experimental evidences based on equilibrium data at four temperatures (298- 328 K) are analyzed for a useful analytical interpretation. The analysis of the data via the advanced model indicates that the number of IBD linked per CoFe2O4/CMC active site (n) varied from 3.65 to 3.83, also demonstrating that the orientation (adsorption geometry) of the IBD dye on CoFe2O4/CMC surface is angled and affected by the temperature. Based on these values, it can be deduced that the adsorption mechanism at all the investigated temperatures is a multi-molecular process. It is also demonstrated that an increment in the temperature leads to a positive evolution of the adsorption capacity (Q(sat)) from 224.81 mg/g at T = 298 K to 289.87 mg/g at T = 328 K, testifying that the adsorption process is overall endothermic. This theoretical evidence is corroborated by the estimation of the adsorption energies (Delta E-1(alpha) and Delta E-2(alpha)), which indicated that physical interactions between IBD molecules and the CoFe2O4/CMC receptor sites and among IBD-IBD molecules take place. Finally, three thermodynamic parameters are determined for a further insight into the interpretation of the adsorption mechanism. The adsorption configurational entropy (S-ad) evolution allows confirming the occurrence of different adsorbed layers (N-C = 1 + N-2), while the Gibbs adsorption free energy (G(ad)) confirmed that the process is spontaneous