Search results for " dielectric spectroscopy"
showing 10 items of 10 documents
Broadband dielectric spectroscopy of 0.4PMN-0.3PSN-0.3PZN ceramics
2007
In this paper, results of the broadband dielectric spectroscopy of 0.4PbMg1/3Nb2/3O3-0.3PbZn1/3Nb2/3O3-0.3PbSc1/2Nb1/2O3(0.4PMN-0.3PZN-0.3PSN) are presented. Dielectric spectra of these solutions were investigated in a broad frequency range from 20 Hz to 100 GHz. Very strong and broad dielectric relaxation was analyzed in terms of distribution of relaxations times, using Tichonov regularization method. It revealed slowing down of the longest relaxation and the mean relaxation times in the agreement with the Vogel-Fulcher law and the Arrhenius law, respectively.
Emerging dynamics in surfactant-based liquid mixtures: octanoic acid/bis(2-ethylhexyl) amine systems.
2012
This work focuses on the dynamic phenomena emerging in self-assembled transient intermolecular networks formed when two different surfactants are mixed. In particular, the relaxation processes in liquid mixtures composed by bis(2-ethylhexyl)amine (BEEA) and octanoic acid (OA) in the whole composition range has been investigated by dielectric spectroscopy and Brillouin spectroscopy. A thorough analysis of all the experimental data consistently suggests that, mainly driven by acid-base interactions arising when the two surfactants are mixed, supra-molecular aggregates formation causes the slowing down of molecular dynamics. This, in turn, reflects to longer-range relaxations. These changes ha…
Broadband Dielectric Spectroscopy of PSN-Rich PMN-PSN Ceramics
2008
The broadband dielectric permittivity of ordered 0.1PMN-0.9PSN and disordered 0.2PMN-0.8PSN ceramics was investigated. The anomaly of dielectric permittivity is clearly seen in the region of 370 K for 0.1 PMN-0.9 PSN at all frequencies. 0.2 PMN-0.8 PSN shows relaxor behaviour with huge frequency dispersion below 350 K. Calculated distribution of relaxation times shows noticeable influence of polar nano regions to the total dielectric spectrum below 320 K with the longest relaxation times edge diverging according to the Vogel-Fulcher law. In 0.1 PMN-0.9 PSN two a little overlapped peaks present in the distribution of relaxation times, influenced by displacive lead motions at high frequencies…
Broad Distribution of Relaxation Times in 0.6PMN-0.4PZN Relaxor Ceramics
2007
In this paper dielectric spectra of 0.6PMN-0.4PZN ceramic obtained from broadband dielectric spectroscopy is presented. Measurements revealed an unusual relaxor like nature. Two different processes in the dielectric spectra have been observed. High frequency, or short relaxation times, behaviour is typical for ferroelectric crystals. Longest relaxation times do not follow Vogel—Fulcher dependence, which is unusual for relaxors.
Dielectric Characterization of Fruit Nectars at Low RF Frequencies
2015
Dielectric properties of apple, apricot, peach, and pear nectars were studied in the frequency range from 15 kHz to 30 MHz and the temperature range from 25 to 60 degrees C. Both the relative dielectric constants and the dielectric loss factors decreased by increasing frequency and increased linearly with increasing temperature with values in the order 10(4)-10(2) and 10(5)-10(2), respectively. The power dissipation densities and the power penetration depths were found to increase linearly with temperature. Power dissipation densities remained essentially constant for all the samples while power penetration depths decreased significantly on increasing frequency. The dependence of each of th…
Infrared and broadband dielectric spectroscopy of PZN-PMN-PSN relaxor ferroelectrics: Origin of two-component relaxation
2006
Dielectric spectra of several solid solutions of $\mathrm{Pb}{\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{Pb}{\mathrm{Sc}}_{1∕2}{\mathrm{Nb}}_{1∕2}{\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{Pb}{\mathrm{Zn}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}$ (PMN-PSN-PZN) relaxor ferroelectrics were investigated in a broad frequency range from $20\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}$ up to $100\phantom{\rule{0.3em}{0ex}}\mathrm{THz}$ by a combination of dielectric spectroscopy $(20\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}\char21{}53\phantom{\rule{0.3em}{0ex}}\mathrm{GHz})$, time-domain terahertz spectroscopy $(0.1\char21{}0.9\phantom{\rule{0.3em}{0ex}}\mathrm{TH…
Applications and Implications of Fractional Dynamics for Dielectric Relaxation
2012
This article summarizes briefly the presentation given by the author at the NATO Advanced Research Workshop on “Broadband Dielectric Spectroscopy and its Advanced Technological Applications”, held in Perpignan, France, in September 2011. The purpose of the invited presentation at the workshop was to review and summarize the basic theory of fractional dynamics (Hilfer, Phys Rev E 48:2466, 1993; Hilfer and Anton, Phys Rev E Rapid Commun 51:R848, 1995; Hilfer, Fractals 3(1):211, 1995; Hilfer, Chaos Solitons Fractals 5:1475, 1995; Hilfer, Fractals 3:549, 1995; Hilfer, Physica A 221:89, 1995; Hilfer, On fractional diffusion and its relation with continuous time random walks. In: Pekalski et al. …
Molecular dynamics in low-molar and polymeric ferroelectric liquid crystals
1991
Broadband dielectric spectroscopy covering the frequency range from 10−1 Hz to 109 Hz was employed to study the molecular dynamics in low-molar and polymeric ferrroelectric liquid crystals. At frequencies below 106 Hz the ferroelectric modes, soft and Goldstone mode are observed. In the frequency regime from 106 Hz to 109 Hz a fast relaxation process is found, which is assigned to the hindered rotation of the mesogens around their long molecular axis. It turns out that the molecular dynamics is not principally different between low-molar and polymeric systems.
Self-assembly in surfactant-based mixtures driven by acid–base reactions: bis(2-ethylhexyl) phosphoric acid–n-octylamine systems
2013
Structural and dynamic features of bis(2-ethylhexyl) phosphoric acid (HDEHP)-n-octylamine (NOA) mixtures as a function of the NOA mole fraction (X-NOA) have been investigated by SAXS, WAXS, IR, dielectric spectroscopy and polarized optical microscopy. In the 0 <= X-NOA < 0.5 range, mixtures are transparent liquids, while the abrupt formation of a waxy solid characterized by an hexagonal bidimensional structure occurs at X-NOA = 0.5. Such a composition-induced phase transition results from the synergetic effect of the progressive increase in number density of ordered HDEHP-NOA nanodomains with X-NOA. Mainly driven by an HDEHP to NOA proton transfer, the increase of structural order with X-NO…
Application of Broadband Dielectric Spectroscopy to Cultural Heritage: characterization and preservation of ancient paper artwork
2016
Within the cultural heritage the characterization and conservation of artworks based on paper represents a significant issue for both restorers and scientists. The paper deterioration is affected by the degree of hydrolytic and oxidative reactions which occur upon aging. Moreover, the durability of cellulose fibers depends on the intrinsic composition/structure of the paper as well as on the conservation conditions, such as temperature and humidity. The structural and dynamical characterization of the cellulose matrix and of the water confined within its pores is therefore of central interest. Our working hypothesis is that WATER DYNAMICS is one of the main determinants of paper degradation…