Nonlinear dielectric properties of copolymers of vinylidene fluoride and trifluoroethylene

Ikeda, Susumu; Kominami, Hiraku; Koyama, Kiyohito; Wada, Yasaku

doi:10.1080/00150198708016963

Cited by 10 publications

(2 citation statements)

References 3 publications

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“…The coefficients a, b, c, ... can be expressed in terms of linear and nonlinear susceptibilities by formally inverting the relation ( 5) and writing P (E) as a power series in E. 11 In Landau theory, close to a second order phase transition one sets a(T ) ∝ T − T 0 , while b, c, ... are constants. Thus, a 1 = const., and b 1 = c 1 = • • • = 0.…”

Section: Thermodynamic Approachmentioning

confidence: 99%

Electrocaloric effect in relaxor ferroelectrics

Pirc¹,

Kutnjak²,

Blinc³

et al. 2011

Journal of Applied Physics

162

111

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The electrocaloric effect (ECE) in normal and relaxor ferroelectrics is investigated in the framework of a thermodynamic approach based on the Maxwell relation and a Landau-type free energy model. The static dielectric response of relaxors is described by the spherical random bond--random field model, yielding the first Landau coefficient a=a(T), which differs from the usual expression for ferroelectrics. The fourth-order coefficient b is treated as a phenomenological parameter, which is either positive or negative due to the anisotropy of the stress-mediated coupling between the polar nanoregions. When b<0, the maximum ECE in a relaxor is predicted near the critical point in the temperature-field phase diagram, whereas in a ferroelectric it occurs at the first order phase transition. The theoretical upper bound on the ECE temperature change is estimated from the values of saturated polarization, effective Curie constant, and specific heat of the material.Comment: 20 pages, 4 figure

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Section: Thermodynamic Approachmentioning

confidence: 99%

Electrocaloric effect in relaxor ferroelectrics

Pirc¹,

Kutnjak²,

Blinc³

et al. 2011

Journal of Applied Physics

162

111

View full text Add to dashboard Cite

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“…The free radicals thus produced may change the chemical structure of the polymer and alter its electrical properties. Numerous publications have dealt with these changes under the influence of ionizing radiation [3][4][5][6][7][8][9][10][11][12][13]. The present study deals with the investigation of gamma irradiation effects in CPVC aiming to modify and improve its electrical properties for different industrial applications using gamma radiation.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the effect of gamma rays on electrical properties of chlorinated poly (vinyl chloride)

Nouh

Abdel‐Naby

2003

Radiation Effects and Defects in Solids

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Dielectric constant, dielectric loss and AC conductivity were measured, in the frequency range 100 Hz to 5 MHz in chlorinated poly (vinyl chloride) (CPVC) before and after exposure to gamma irradiation at doses between 5.0 KGy and 50.0 KGy. The frequency dependencies of e 0 , e 00 and s AC at 30 C were investigated. A relaxation peak in the dielectric loss and a corresponding step in the dielectric constant have been observed, in the frequency ranges 10 3 Hz to 10 4 Hz. The dielectric constant e 0 , dielectric loss e 00 and AC conductivity s AC are also found to increase at heating up to 100 C. In addition the effect of gamma irradiation on the frequency dependencies of e 0 , e 00 and s AC was measured at room temperature. The gamma irradiation leads to an increase in the efficiency of soft segments. Furthermore, the DC electrical conductivity of both the irradiated and non-irradiated samples was investigated. The induced electrical conductivity and the activation energy were measured, at various temperatures, as a function of gamma dose. It was found that the gamma radiation has a definite effect on the DC conductivity of the CPVC polymer.

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The diffuse behavior of the ferroelectric transition in poly(vinylidene fluoride‐trifluoroethylene) copolymers

Moreira

Lobo

Medeiros‐Ribeiro

et al. 1994

J Polym Sci B Polym Phys

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The ferroelectric‐to‐paraelectric phase transition in poly(vinylidene fluoride‐trifluoroethylene) copolymers has been investigated using calorimetric and dielectric technics. In these materials, as it is well known, the ferro‐ and paraelectric phases coexist at large temperature intervals, which produces a smearing of the physical anomalies within the transition region. Thus, in order to treat our data, we have used an extended Landau‐Devonshire treatment, which has provided a quantitative analysis of the macroscopic behavior of the systems. In particular, the Landau expansion parameters, the sample crystallinities, the spontaneous polarizations, and the coercive electric fields have been estimated for the copolymers with 25, 30, and 40 mol% of trifluoroethylene. © 1994 John Wiley & Sons, Inc.

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Nonlinear dielectric properties of copolymers of vinylidene fluoride and trifluoroethylene

Cited by 10 publications

References 3 publications

Electrocaloric effect in relaxor ferroelectrics

Electrocaloric effect in relaxor ferroelectrics

Investigation of the effect of gamma rays on electrical properties of chlorinated poly (vinyl chloride)

The diffuse behavior of the ferroelectric transition in poly(vinylidene fluoride‐trifluoroethylene) copolymers

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