This study focuses on the effect of anatase titania acting as nanofiller on the relaxation
dynamics and ionic conductivity behavior in polymer nanocomposite
electrolyte based on PEO20–LiCF3SO3–TiO2. Using broadband dielectric spectroscopy,
the dynamics of ion transport mechanism is studied over a wide range
of temperature and frequency. Polymer salt complex exhibit the direct
current (dc) conductivity σdc = 3.760 × 10–7 S cm–1 at 303 K. But with the addition
of 8 wt % TiO2, a 2-order increase in the magnitude of
dc conductivity is observed at the same temperature. Ion conduction
mechanism is analyzed employing a complex relative permittivity as
well as modulus formalisms. Isotherms of real part of conductivity
spectra and dielectric loss spectra are analyzed to explain the observed
first and second universalities in the ion conduction mechanism. Kramer–Krönig
approach is used to discuss the crossover between the two universalities.
Ratner’s classical approach in combination with modified Nernst–Einstein
relation is used to correlate the coupling nature of polymer segmental
relaxation and ionic transport mechanism. Successful scaling of conductivity
spectra using the Summerfield approach and imaginary modulus spectra
using maxima normalization approach indicate that ionic transport
mechanism is a thermally activated temperature-independent phenomenon.
Temperature-dependent dc conductivity is explained using a mismatch-generated
relaxation for the accommodation and transport of ions concept as
well as Vogel–Tammann–Fulcher relation to get a better
insight into the ion conduction mechanism. With a comprehensive study
of the relaxation events and ionic conductivity, a close coupling
between polymer segmental relaxation and ionic conduction in polymer
nanocomposite electrolytes is observed.
Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of wellregulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1 − x) Na 0.5 Bi 0.5 TiO 3 − x BaTiO 3 (0.00 ⩽ x ⩽ 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO 3 into Na 0.5 Bi 0.5 TiO 3 , it induces a structural phase transition from R3c (a single phase) to R3c + P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our x-ray Rietveld refinement and Raman spectroscopic results. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x. In the prepared solid solution, an anomalous enhancement of remnant polarization (2P 0 r ) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field E 0 C was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples.
A series of ion conducting polymer-clay composites has been prepared using a solution casting technique. Relaxation dynamics and the ionic transport mechanism are systematically studied employing broadband dielectric spectroscopy over a wide frequency and temperature range. Among different phenomenological and theoretical models for ion conduction in disordered ionic conductors, conductivity isotherm spectra are analysed using the modified Almond-West and random free energy barrier model. Conductivity scaling suggests that the ionic transport mechanism is independent of temperature, and a similar inference is also obtained using scaled electrical modulus spectra. DC conductivity along with conductivity and segmental relaxation time following the Vogel-Tammann-Fulcher relationship suggests coupling between the ionic transport and segmental relaxation processes. Electrical modulus and dielectric formalism are used to understand the conductivity and segmental relaxation processes, respectively. The presence of first and second universality in the ionic transport mechanism is discussed using the real part of conductivity spectra and dielectric loss spectra. The crossover between the first and second universality is explained using the Kramer-Krönig approach. The ion diffusion coefficient is investigated using Ratner's classical approach in combination with the modified Stokes-Einstein relationship to correlate the coupled nature of the ion conduction mechanism and polymer segmental motion.
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