Dipolar Glass Research Articles

New poly(itaconate)s with bulky pendant groups as candidates for “all-polymer” dielectrics

This work presents the synthesis and characterizaiton of three new poly(itaconate)s containing nitriles functional groups as high dipole moment entities and three different cycloalkyl pendant groups, in order to increase the rigidity of the system and therefore, their dipolar glass polymer temperature interval. The structural, thermal and dielectric characterization has been carried out in terms of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS), respectively. All polymers showed good thermal properties with degradation temperatures above 250 °C, presenting higher glass transition temperatures than those of recently reported poly(itaconate)s. Regarding dielectric properties, dielectric constant values between 4.0 and 4.3 (at 25 °C and 1 kHz) and relative low loss tangent values (below 0.01) were obtained. BDS measurements showed in all cases, notorious sub-glass transitions even at temperatures below −100 °C, resulting in a broad temperature interval in which these polymers could work without high dielectric losses. Therefore, these materials seem to be good candidates for dielectric applications such as energy storage, among others.

Dipole Glass Phase in an Isolated Hydrogen-Bonded Mixed Crystal [(NH4)1−x Rbx]3H(SO4)2 (x = 0.58)

[(NH4)1−xRbx]3H(SO4)2 mixed crystals were investigated by dielectric constant measurement and Raman spectroscopy from room temperature to 7 K. In contrast to the result of (NH4)3H(SO4)2 (x = 0) showing multiple phase transitions, [(NH4)1−xRbx]3H(SO4)2 (x = 0.58) mixed crystal does not show any remarkable dielectric anomaly but a weak dielectric dispersion below 40 K, which is characterized by the Arrhenius law. From the measurement of the Raman spectra of both crystals, it is confirmed that the [(NH4)1−xRbx]3H(SO4)2 (x = 0.58) mixed crystal shows a global symmetry conservation between the two spectra measured at room temperature and at 20 K while the (NH4)3H(SO4)2 crystal exhibits drastic structural changes associated with the sequence of the phase transitions. It is concluded that [(NH4)1−xRbx]3H(SO4)2 (x = 0.58) mixed crystal shows a new dipole glass phase in the isolated hydrogen-bonded system.

Dipolar Glass Polymers Containing Polarizable Groups as Dielectric Materials for Energy Storage Applications. A Minireview.

Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R−S(=O)2−R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and β relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as “dipolar glass polymers”. Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed.

Synthesis of new poly(itaconate)s containing nitrile groups as high dipolar moment entities for the development of dipolar glass polymers with increased dielectric constant. Thermal and dielectric characterization

This work presents the synthesis of new poly(itaconate)s containing one or two nitrile pendant groups through conventional radical polymerization. To the best of our knowledge, this is the first time in which the synthesis of poly(itaconate)s containing nitrile groups is reported in the literature. The effect of nitrile groups on the main properties is analyzed. Polymer structures were confirmed by Fourier transform infrared spectroscopy (FTIR), 1H and 13C NMR. Molecular weights were measured by size exclusion chromatography (SEC), while thermal characterization was achieved by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Dielectric properties were measured using broadband dielectric spectroscopy at different temperatures. Polymers with one or two nitrile groups presented dielectric constant values (at 25 °C and 1 kHz) of around 7 and 12.5, respectively, with relatively low dielectric losses with values below 0.02. BDS measurements showed notorious sub-glass transitions attributed to the movement of the dipolar groups under the electric field, even below −100 °C, allowing to achieve dielectric constant values above the average for polymers even at extremely low temperatures. Therefore, these materials could be considered as good candidates for energy storage applications.

Dipole glass in chromium-substituted bismuth pyrostannate

To establish the existence of dipole glass in the chromium-substituted bismuth pyrostannate solid solutions, the frequency and temperature dependences of the permittivity have been measured in the temperature range of 300–750 K. The field and dynamic dependences of polarization in the temperature range of 80–550 K have been determined. Using the Raman scattering spectra, the absence of inversion center has been established. The maximum of electrical resistance has been found in the vicinity of the dipole moment freezing point. The carrier type has been determined from the thermopower data. The polarization relaxation is shown to be nonexponential. The experimental data are explained within the model of dipole glass in the α- phase and the model of charged crystalline domain walls with the electron-polarization relaxation mechanism above the α–β structural transition.

Facile synthesis of fluorinated poly(arylene ether nitrile) and its dielectric properties

ABSTRACTA new class of specialty polymer, fluorinated poly(arylene ether nitrile) (PAEN‐F), was synthesized via the aromatic nucleophilic substitution reaction. Due to its rigid structure, PAEN‐F exhibited enhanced heat resistance and thermal stability. Consequently, the glass‐transition temperature and initial degradation temperature of PAEN‐F reached as high as 179°C and 554°C, respectively. PAEN‐F also showed excellent solubility in low‐boiling solvents owing to fluorine groups and the nonplanar structure in the repeat unit. Due to its strong 6F dipoles, PAEN‐F exhibited a high dielectric constant (ɛr) of 3.6, a high electrical breakdown strength of 346 MV/m, and a reasonably low dissipation factor (tan δ) of 0.014 at 25°C and 100 Hz. Therefore, this dipolar glass polymer is promising for high‐temperature and low‐loss electric energy storage applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46837.

Dielectric relaxation in pure and doped with Cu lead germanate single crystal

Dielectric permittivity of pure and doped with copper lead germanate Pb5Ge3O11 (PGO) crystal was studied in wide frequency (20 Hz to 3 GHz) and temperature (120 K to 450 K) range. The ferroelectric phase transition in PGO crystals is mixed “order-disoder” and displacive. Second order phase transition temperature shifts to lower temperature with increase the concentration of Cu2+ dopant. At low temperatures the dielectric relaxation caused by off center Cu2+ ion dynamics was detected. Dielectric dispersion in PGO:Cu crystals is attributed to domain wall dynamics and dipole glass freezing. It is shown that the domain relaxation requires lower energy then for the random freezing dipoles.

High Dielectric Constant Sulfonyl-Containing Dipolar Glass Polymers with Enhanced Orientational Polarization

Dipolar glass (DG) polymers, which utilize sub-Tg orientational polarization (Tg is the glass transition temperature) to enhance dielectric constants, are promising candidates for use in advanced e...

Colossal magnetostriction and electrostriction of bismuth-substituted neodymium iron garnet films

Electro- and magnetostriction mechanisms and temperature behavior of the length of bismuth-substituted neodymium iron garnet films on glass and gallium gadolinium garnet have been investigated. Electric- and magnetic-field and temperature dependences of the electro- and magnetostriction constants have been determined. It has been established that the magnetostriction constant changes its sign upon temperature variation. The experimental data are explained using a model of dipole glass with the magnetoelectric and magnetoelastic interaction.

Dipolar glass-like dielectric response of nanocrystalline Sr0.95Nd0.05Fe12-xScxO19 hexaferrites

Recently reported magnetic quantum paraelectric properties in M-type hexaferrite single crystals have encouraged us to study the dielectric response of SrFe12O19 nanocrystallites down to the temperature of 10 K. As Sc-induced multiferroicity, promising for electromagnetic control, has been reported in bulk and films of hexaferrites, we also studied the size effect in dielectric response of Sr0.95Nd0.05Fe12-xScxO19 nanocrystallites with x = 0.36, 1.08, and 1.56. The nanopowders were obtained by citric method and the phase purity and the microstructure were controlled using X-ray diffraction and scanning electron microscopy. No clear evidence of quantum paraelectric behavior has been observed in temperature variation of dielectric permittivity of SrFe12O19 nanopowder. In the case of Nd-stabilized Sc-doped nanocrystallites, a low-temperature dielectric relaxation, similar to that in dipolar glasses, has been discovered. Activation energy of 62.5 meV was obtained for the lowest doping level and a modest increase in the energy was found at higher Sc concentrations. We relate the low-temperature relaxation in Sc-doped hexaferrite nanopowder to dielectric displacive polarization at the 4e Wyckoff sites modified by Sc-ions substituting the ferric ions in 4f2 and 12k positions.

Nature of Ferroelectric Behavior in Main-Chain Dipolar Glass Nylons: Cooperative Segmental Motion Induced by High Poling Electric Field

Main-chain dipolar glass polymers such as aromatic nylons are promising for high energy density and low loss dielectric applications because of the limited, noncooperative oscillation of highly dipolar amide groups. However, quenched aromatic nylons have been reported to exhibit significant ferroelectric switching upon high field poling. It is desirable to suppress ferroelectric switching for electric energy storage application, and this requires a fundamental understanding of the nature of ferroelectric behavior in dipolar glass nylons. In this work, a nearly 100% amorphous aromatic nylon, Selar, was used to investigate the origin of ferroelectricity in glassy nylons. Using Fourier transform infrared spectroscopy, it was found that hydrogen-bonding strength played an important role in the ferroelectric switching of amide dipoles in the loosely packed glassy matrix. When hydrogen bonding was weak such as in the quenched film, significant ferroelectric switching took place. In contrast, quenched and anneal...

Phase Diagram and Dielectric Properties of (1–x)Ba(Ti1–yZr y )O3 · xPbTiO3 Ceramics

Ceramic (1–x)Ba(Ti1–yZry)O3 · xPbTiO3 (0 ≤ x, у ≤ 1) samples have been characterized by X-ray diffraction and dielectric measurements. The results have been used to map out the phase diagram of the system, which demonstrates the variation in the phase composition of the samples. It has been shown that, in the composition regions adjacent to the BaTiO3–PbTiO3 side and BaZrO3 corner of the composition triangle, the samples consist of perovskite solid solutions that have tetragonal and cubic structures, respectively, at room temperature. In the intermediate composition region, the samples consist of different perovskite solid solutions similar in composition and structure. We have obtained composition dependences of the unit-cell symmetry and parameters for the solid solutions, their ferroelectric Curie temperature TC, characteristic dielectric relaxation temperatures, dielectric permittivity e, and dielectric loss tangent tanδ (at temperatures from 100 to 800 K and frequencies from 25 to 106 Hz) and analyzed the evolution of their dielectric properties with increasing BaZrO3 content: from ferroelectric to properties of ferroelectric relaxors, reentrant relaxors, and dielectric relaxors of the dipole glass type.

High‐Temperature and High‐Energy‐Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6‐dimethyl‐1,4‐phenylene oxide)

AbstractA new class of high‐temperature dipolar polymers based on sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SO2‐PPO) was synthesized by post‐polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (Tg≈220 °C), the dipolar polarization of these SO2‐PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm−3. Owing to its high Tg , the SO2‐PPO25 sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m−1 was 92 %. Therefore, these dipolar glass polymers are promising for high‐temperature, high‐energy‐density, and low‐loss electrical energy storage applications.

High-Temperature and High-Energy-Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6-dimethyl-1,4-phenylene oxide).

A new class of high-temperature dipolar polymers based on sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SO2 -PPO) was synthesized by post-polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (Tg ≈220 °C), the dipolar polarization of these SO2 -PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm-3 . Owing to its high Tg , the SO2 -PPO25 sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m-1 was 92 %. Therefore, these dipolar glass polymers are promising for high-temperature, high-energy-density, and low-loss electrical energy storage applications.

Comparative Monte-Carlo simulations of charge carrier transport in amorphous molecular solids as given by three most common models of disorder: The dipolar glass, the Gaussian disorder, and their mix.

We have performed Monte-Carlo simulations of the charge carrier transport in a model molecularly doped polymer using three most popular hopping theories (the dipolar glass model, the Gaussian disorder model, and an intermediate between them) in a wide range of applied electric fields and temperatures. Time of flight transients have been computed and analyzed in logarithmic coordinates to study the Poole-Frenkel field dependence, the non-Arrhenius mobility temperature dependence, and the nondispersive versus dispersive current shapes. We also have made an attempt to estimate the total disorder energy directly from simulation data at the lowest electric field thus checking the consistency of the model fitting. Computational results have been compared with the analytical and experimental information available in the literature.

Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites

Hexagonal ferrites do not only have enormous commercial impact ({\pounds}2 billion/year in sales) due to applications that include ultra-high density memories, credit card stripes, magnetic bar codes, small motors and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbFe$_{12-x}$Ga$_x$O$_{19}$ to zero by chemical substitution $x$. The phase transition boundary is found to vary as $T_N \sim (1-x/x_c)^{2/3}$ with $x_c$ very close to the calculated spin percolation threshold which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven. We find that this produces a form of compositionally-tuned, insulating, ferrimagnetic quantum criticality. Close to the zero temperature phase transition we observe the emergence of an electric-dipole glass induced by magneto-electric coupling. The strong frequency behaviour of the glass freezing temperature $T_m$ has a Vogel-Fulcher dependence with $T_m$ finite, or suppressed below zero in the zero frequency limit, depending on composition $x$. These quantum-mechanical properties, along with the multiplicity of low-lying modes near to the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.

Quantum phase transitions in Ba(1−x)CaxFe12O19 ( 0≤x≤0.10 )

The ground state of BaFe12O19 (BFO) is controversial as three different quantum states, namely quantum paraelectric, frustrated antiferroelectric and quantum electric dipole liquid (QEDL), have been proposed. We have investigated the quantum critical behavior of BFO as a function of chemical pressure (a non-thermal variable) generated by smaller isovalent ion Ca2+ at the Ba2+ site. Analysis of synchrotron x-ray diffraction data confirms that Ca2+ substitution generates positive chemical pressure. Our dielectric measurements reveal that Ca2+ substitution drives BFO away from its quantum critical point (QCP) and stabilizes a quantum electric dipolar glass state whose dielectric peak temperature (Tc) increases with increasing Ca2+ content as Tc ~ (x-xc)1/2, a canonical signature of quantum phase transitions. Our dielectric measurements reveal that pure BFO is slightly away from its QCP with a Tc of 2.91 K. Specific heat measurements reveal excess specific heat of non-Debye and non-magnetic origin with linear temperature dependence below Tc which could be due to QEDL state of BFO.

Baric transformations of anomalies of dielectric permeability of CuСr<sub>0,5</sub>In<sub>0,5</sub>P<sub>2</sub>S<sub>6</sub> layered crystals

Purpose: The investigation of the nature of the dipole glass state in ferroelectrics has become one of the most interesting and important areas in solid state physics in recent years. Layered crystals of solid solutions based on CuCrP 2 S 6 and compounds are very convenient materials for studying the effects of relaxation dynamics caused by dipole disordering. With the change of the chemical composition of solid solutions, we can observe a transformation from dipole ordering with a long-range order, (a ferroelectric CuInP 2 S 6 in and an anti-ferroelectric in CuCrP 2 S 6 ) to a state of dipole glass with a relaxation behavior caused by the freezing of ferroactive ions in the crystal lattice. Based on the investigations of dielectric spectroscopy (10 mHz-3 GHz) in mixed Cu(In x Cr 1-x )P 2 S 6 crystals, it was found that the phase changing point between the ferroelectric phase and the dipole glass phase lies between x=0.5 and 0.7 , and the corresponding point between the state of the dipole glass and the anti-ferroelectric phase is between x=0.4 and 0.2. The main aim of this study is to investigate the effect of high hydrostatic pressure on the temperature dependences of dielectric properties of CuСr 0,5 In 0,5 P 2 S 6 crystals, in which the state of dipole glass occurs at atmosphere pressure according to the phase x , T -diagram . Methods: Studied CuСr 0,5 In 0,5 P 2 S 6 crystals were grown by the gas transport reaction method. For the dielectric measurement polished plate like crystals were used. All measurements were performed in a direction perpendicular to the layers. The complex dielectric permittivity e∗ was measured using an HP4262A capacitance bridge at the frequency 1 MHz. All measurements have been performed on cooling and heating mode with a temperature rate 0.5 K/min. Silver paste has been used for contacting. Hydrostatic pressure was applied a high-pressure chamber, its value being controlled within ±1MPa. Scanning electron microscopy (SEM) studies combined with energy dispersive X-ray spectroscopy (EDX) were performed using a SEM JEOL 7000F microscope. Results: Studies of a complex dielectric permittivity e* of CuСr 0,5 In 0,5 P 2 S 6 crystals with different values of hydrostatic pressure were performed in a wide temperature range 77 K 300MPa, two anomalies of the real part of the dielectric constant are revealed. One, at lower temperatures. corresponds to the transition to the state of a dipole glass, the other-at higher temperatures, is a ferroelectric phase transition induced by hydrostatic pressure. The Value of the baric temperature shift of the ferroelectric phase transition for CuСr 0,5 In 0,5 P 2 S 6 crystals induced by high hydrostatic pressure d Tc /d p =0,18 K/MPa is close to the similar value of d Tc /d p =0,21 K/MPa and d Tc /d p =0,29 K/MPa for crystals CuInP 2 S 6 and CuСr 0,3 In 0,7 P 2 S 6 , respectively. Conclusions: Based on the studies of temperature dependences of dielectric permittivity of layered crystals at high hydrostatic pressure, the baric behavior of the temperatures of the anomalies of dielectric permittivity of crystals CuСr 0,5 In 0,5 P 2 S 6 is established. Hydrostatic pressure induces the appearance of an anomaly of dielectric constant, which corresponds to a ferroelectric phase transition. p , T phase diagram of these crystalls was built, and pressure coefficients for the phase transition temperature shift were determined. The phase transition temperature in crystals CuСr 0,5 In 0,5 P 2 S 6 determined by extrapolation of the baric dependence of the temperature of the ferroelectric phase transition to atmospheric pressure is equal to T c =162K. The phase x , T diagram of Cu(In x Cr 1-x )P 2 S 6 solid solutions was built. The concentration shift of the temperature of the ferroelectric phase transition for solid solutions of Cu(In x Cr 1-x )P 2 S 6 can be well described by the equation Т с ( х )=314,6-3,5× х +0,009× х 2 ( х, mol.%)

Analytic Modeling of Field Dependence of Charge Mobility and Applicability of the Concept of the Effective Transport Level to an Organic Dipole Glass

An analytic model for the field dependence of charge mobility is developed within the long-range-correlated disorder model of a dipole glass. Release of a charge carrier from a deep state is considered as hopping drift and diffusion in a quasi-Coulomb potential well. The analytic results, containing only one numerical parameter obtained from independent simulation, are in good agreement with the fit to the Monte-Carlo simulations. The developed approach justifies applicability of the concept of the effective transport level for the modeling of organic materials with large molecular dipoles.

Dipole glass behavior of Fe-doped SrTiO3 ceramics

The effects of Fe ions incorporation into the Sr and Ti sites of SrTiO3 ceramics on the dielectric properties are studied in this work. It is found that the dielectric properties of the samples are sensitive to the components. Compared to SrTi0.9Fe0.1O3−δ with paraelectric property, Sr0.98Ti0.9Fe0.1O3−δ and Sr0.98Ti0.92Fe0.1O3−δ present dielectric relaxations at low temperature. After carefully analyzing the dielectric spectra by Arrhenius law and Power law, the dielectric relaxations are mainly attributed to the relaxation polarizations of defect dipoles formed by the off-center Fe ions at the Sr-sites and oxygen vacancies, and the dipole glass behavior are identified at low temperature.