Dipolar Glass Research Articles

Enhanced high-temperature energy storage performances in polymer dielectrics by synergistically optimizing band-gap and polarization of dipolar glass

Polymer dielectrics play an irreplaceable role in electrostatic capacitors in modern electrical systems, and have been intensively studied with their polarization and breakdown strength (Eb) optimized for high discharged energy density (Ud) at elevated temperatures. Small molecules have been explored as fillers, yet they deteriorate thermal stability of matrix which limits their optimal loading to ~1 wt%. Herein, we develop a polymer blend dielectric consisting of common polyimide and a bifunctional dipolar glass polymer which are synthesized from two small molecule components with wide band-gap and large dipole moment. The bifunctional dipolar glass with large molecular weight not only maintains thermal stability of polymer blends even at a high loading of 10 wt%, but also induces substantial enhancement in polarization and Eb than any of individual components does, achieving an ultrahigh Ud of 8.34 J cm−3 (150 °C) and 6.21 J cm−3 (200 °C) with a charge-discharge efficiency of 90%.

A highly polarizable concentrated dipole glass for ultrahigh energy storage

Relaxor ferroelectrics are highly desired for pulse-power dielectric capacitors, however it has become a bottleneck that substantial enhancements of energy density generally sacrifice energy efficiency under superhigh fields. Here, we demonstrate a novel concept of highly polarizable concentrated dipole glass in delicately-designed high-entropy (Bi1/3Ba1/3Na1/3)(Fe2/9Ti5/9Nb2/9)O3 ceramic achieved via substitution of multiple heterovalent ferroelectric-active principal cation species on equivalent lattice sites. The atomic-scaled polar heterogeneity of dipoles with different polar vectors between adjacent unit cells enables diffuse reorientation process but disables appreciable growth with electric fields. These unique features cause superior recoverable energy density of ~15.9 J cm−3 and efficiency of ~93.3% in bulk ceramics. We also extend the highly polarizable concentrated dipole glass to the prototype multilayer ceramic capacitor, which exhibits record-breaking recoverable energy density of ~26.3 J cm−3 and efficiency of ~92.4% with excellent temperature and cycle stability. This research presents a distinctive approach for designing high-performance energy-storage dielectric capacitors.

Combining linear and cyclic sulfones as a strategy for elaborating more efficient high-dielectric polymer materials: A second case of dipolar glass copolymers

Motivated by the excellent features exhibited by sulfone functional groups in the development of high-dielectric polymer materials, this work assesses the combination of linear and cyclic sulfone structures through copolymerization to prepare novel polymer materials exhibiting high dielectric constants (ԑr'), low dissipative behavior, and improved thermal properties. Five new polymethacrylate-based copolymers with varying compositions were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. The correct structure and macromolecular nature of the devised materials were confirmed by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H/13C NMR), and gel permeation chromatography (GPC), while their thermal properties were evaluated using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). All specimens exhibited adequate thermal properties for most capacitor applications in terms of onset degradation (Ti) and glass transition (Tg) temperatures. All materials degraded well above 250 °C, with increased Ti and Tg values depending on the final composition of the cyclic sulfone monomer in the material. The incorporation of cyclic sulfones not only increased the thermal robustness of the specimens but also raised their Tg values to as high as 189 °C, notably expanding the range of temperatures where these systems can operate without dissipative phenomena. More importantly, broadband dielectric spectroscopy (BDS) revealed that all samples exhibited dielectric properties notably superior to those of conventional polymer materials, with high ԑr' values between 6.0 and 8.9 (at 25 °C and 1 Hz) and low loss factors (Tan(δ) < 0.018). Overall, the present work successfully demonstrates the advantages of including cyclic structures with high dipole moments in polymeric backbones, offering a new strategy to enhance the thermal and dielectric properties of high-dielectric polymer materials.

Construction of molecular semiconductor traps to improve the energy storage performance of novel cyanopolynorbornene

To meet the demand of film capacitors in harsh condition applications, research workers devote their effort to develop high temperature resistant polymer dielectrics with high energy density. In this paper, a new type of dipole glass polymer, polynorbornene containing cyano-group side chain (PDMBN) is prepared by ring opening metathesis polymerization. The high dipole moment of the cyano-group possesses high polarization, resulting in that the discharge energy density (Ud) of 8.6 J/cm3 and efficiency of 84 % are found in the PDMBN at room temperature. Via using three organic semiconductors with increased electron affinity (NBTI, NBTI-SO2 and NBTI-2SO2) as the fillers, the energy storage properties of PDMBN matrix are further improved due to the binding effect of free electrons. In addition, the interfacial barrier height is inversely proportional to the temperature, electric field and electron affinity of fillers. As a result, 0.7- wt% NBTI-SO2/PDMBN achieves a maximal Ud of 11.6 J/cm3 at 600 MV/m and room temperature. At elevated temperatures, the conduction loss of polymer PDMBN increases sharply, causing a rapid decline in energy storage performance. Nevertheless, the maximum Ud of 0.7-wt%NBTI/PDMBN composite film at 100 °C and 150 °C can reach 6.2 J/cm3 and 4.5 J/cm3, respectively. This study is helpful for the design of polynorbornene dielectrics, and provides an important reference for the construction of carrier traps in polymer dielectrics at high temperature.

Revealing Dynamic Behavior in High Dielectric Poly(thiourethane)-Based Vitrimer-like Materials.

Here, we have explored covalent adaptable networks (CANs) comprising poly(thiourethane)-based systems (PTUs). The PTUs were synthesized through the combination of thiol and isocyanate monomers in stoichiometric proportions, in the presence of dibutyltin dilaurate (DBTDL) as catalyst. Dynamic mechanical analysis (DMA) provided detailed insight into the vitrimeric behavior. Through these investigations, we evaluated the viscoelastic, thermomechanical, and vitrimeric properties. Additionally, broadband dielectric spectroscopy (BDS) revealed the various relaxation processes inherent in such vitrimer-like materials. We methodically examined the evolution of each relaxation in every prepared sample to comprehend the operational mechanisms in these vitrimer-like systems. Our findings underscore that depending on the PTU formulation, the glass transition temperature (Tg) and the topology freezing transition temperature (Tv) can be effectively distinguished and studied. Considering the high dipole moment of the dynamic bonds present in these systems, there is potential for utilizing them as dielectric materials working under the concept of dipolar glass polymers. Furthermore, the reversibility exhibited by their inner chemical structures positions them as promising candidates for active layers in capacitor devices, particularly for energy-related applications, with the ability to be recyclable while maintaining almost invariant both their mechanical and dielectric properties, thus promoting the extension of the lifespan of electronic devices.

Synthesis, X-ray diffraction and dielectric studies of the ceramic samples (1−x)BaTiO3⋅xPbFe2/3W1/3O3 (0≤x≤1) system

Ceramic samples of the ([Formula: see text])BaTiO3⋅xPbFe[Formula: see text]W[Formula: see text]O3, [Formula: see text] (([Formula: see text])BT⋅xPFW) system were synthesized by solid-state reactions method. The samples were characterized by X-ray diffraction (XRD) and dielectric studies, as well as by the measurements of the thermally stimulated depolarization currents (TSDC). It was found that the predominant phase in the samples is presented by the (Ba[Formula: see text]Pbx)(Ti[Formula: see text]Fe[Formula: see text]W[Formula: see text])O3 solid solutions with a perovskite structure, herewith the samples with [Formula: see text] are practically single-phase, and with [Formula: see text] contain the impurity phase BaWO4 (up to 15 mass.% at [Formula: see text]–0.90). Information has been obtained about the changes in the structural and dielectric characteristics of the solid solutions with the change of their composition. It is established that the solid solutions crystal lattice symmetry at 296 K changes from tetragonal at [Formula: see text] to cubic at [Formula: see text]. An increase in the PFW content in solid solutions causes a gradual change in their properties from ferroelectric at [Formula: see text] to relaxor ferroelectric at [Formula: see text], and then to properties similar to those of the dipole glass with weak or zero correlation between dipoles at [Formula: see text]. The addition of BT to PFW leads to rather quick degradation of the relaxor ferroelectric properties of PFW in the region [Formula: see text]–1.0.

Effect of chemical intercalation on ferroelectricity in van der Waals layered CuInP2S6

Chemical intercalation brings about intriguing opportunities to tailor the properties of van der Waals (vdW) layered materials by crafting molecular composite at an atomic scale. Despite a plethora of reports on various materials, the chemical intercalation effect on long-range ferroelectric order remains scarcely explored. Herein, we report the construction of hybrid supercrystal based on a model vdW ferroelectric, CuInP2S6 by molecular intercalation. Although the out-of-plane lattice structure remains commensurate, its ferroelectric polarization is largely destroyed by the chemical intercalation, as confirmed by combined piezoresponse microscopy and Raman spectroscopy. Alternatively, we observed a dipole glass transition at about 280 K by dielectric spectroscopy and correlated it with the Raman analysis. This work highlights the impact of chemical intercalation on collective ferroic orders and paves the routes for creating artificial hybrid crystals by incorporating functional molecules.

High-Temperature Ferroic Glassy States in SrTiO_{3}-Based Thin Films.

Disordered ferroics hold great promise for next-generation magnetoelectric devices because their lack of symmetry constraints implies negligible hysteresis with low energy costs. However, the transition temperature and the magnitude of polarization and magnetization are still too low to meet application requirements. Here, taking the prototype perovskite of SrTiO_{3} as an instance, we realize a coexisting spin and dipole reentrant glass states in SrTiO_{3} homoepitaxial films via manipulation of local symmetry. Room-temperature saturation magnetization and spontaneous polarization reach ∼ 10 emu/cm^{3} and ∼ 25 μC/cm^{2}, respectively, with high transition temperatures (101K and 236K for spin and dipole glass temperatures and 556K and 1100K for Curie temperatures, respectively). Our atomic-scale investigation points out an underlying mechanism, where the Ti/O-defective unit cells break the local translational and orbital symmetry to drive the formation of unusual slush states. This study advances our understanding of the nature of the intricate couplings of ferroic glasses. Our approach could be applied to numerous perovskite oxides for the simultaneous control of the local magnetic and polar orderings and for the exploration of the underlying physics.

Glassy Properties of the Lead-Free Isovalent Relaxor BaZr0.4Ti0.6O3

Glassy dielectric properties were investigated in lead-free BaZr0.4Ti0.6O3 (BZT40) ceramic samples using dielectric spectroscopy in the frequency range of 0.003 Hz–1 MHz and at temperatures of 10 K &lt; T &lt; 300 K. Measurements of the quasistatic dielectric polarization in bias electric fields up to ~28 kV/cm suggested that a ferroelectric state could not be induced, in contrast to the case of canonical relaxors such as PMN. The quasistatic dielectric and freezing dynamics results for the above field amplitudes showed that BZT40 effectively behaves as a dipolar glass. The relaxation spectrum was analyzed employing a frequency–temperature plot, which showed that the longest relaxation time obeyed the Vogel–Fulcher relation τ=τ0expE0/T−T0, with a freezing temperature of 76.7 K. The shortest relaxation time, in contrast, was characterized by a freezing temperature value close to 0 K, implying an Arrhenius-type behavior. The higher value of the polarization and the nonlinear third-order dielectric coefficient ε3 indicated a shift from a pseudospin glass behavior observed for BaZr0.5Ti0.5O3 (BZT50) toward a classical relaxor ferroelectric state.

Hybrid Improper Ferroelectricity in Columnar (NaY)MnMnTi4 O12.

We show that cation ordering on A site columns, oppositely displaced via coupling to B site octahedral tilts, results in a polar phase of the columnar perovskite (NaY)MnMnTi4 O12 . This scheme is similar to hybrid improper ferroelectricity found in layered perovskites, and can be considered a realisation of hybrid improper ferroelectricity in columnar perovskites. The cation ordering is controlled by annealing temperature and when present it also polarises the local dipoles associated with pseudo-Jahn-Teller active Mn2+ ions to establish an additional ferroelectric order out of an otherwise disordered dipolar glass. Below TN ≈12 K, Mn2+ spins order, making the columnar perovskites rare systems in which ordered electric and magnetic dipoles may reside on the same transition metal sublattice.

Hybrid Improper Ferroelectricity in Columnar (NaY)MnMnTi4O12

AbstractWe show that cation ordering on A site columns, oppositely displaced via coupling to B site octahedral tilts, results in a polar phase of the columnar perovskite (NaY)MnMnTi4O12. This scheme is similar to hybrid improper ferroelectricity found in layered perovskites, and can be considered a realisation of hybrid improper ferroelectricity in columnar perovskites. The cation ordering is controlled by annealing temperature and when present it also polarises the local dipoles associated with pseudo‐Jahn–Teller active Mn2+ ions to establish an additional ferroelectric order out of an otherwise disordered dipolar glass. Below TN≈12 K, Mn2+ spins order, making the columnar perovskites rare systems in which ordered electric and magnetic dipoles may reside on the same transition metal sublattice.

Ultrahigh thermal stability of dielectric permittivity in 0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Ti0.875Nb0.125)O3

0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Nb0.125Ti0.875)O3 ceramics with a pseudo-cubic structure and re-entrant dipole glass behavior have been investigated via x-ray diffraction and dielectric permittivity–temperature spectra. It shows excellent dielectric–temperature stability with small variations of dielectric permittivity (±5%, 420–802 K) and dielectric loss tangent (tanδ &amp;lt; 2.5%, 441–647 K) in a wide temperature range. Three dielectric anomalies are observed from 290 to 1050 K. The low-temperature, weakly coupled re-entrant relaxor behavior was described using the Vogel–Fulcher law and the new glass model. The mid- and high-temperature dielectric anomalies are characterized by isothermal impedance and electrical modulus. The activation energy of both dielectric relaxation and conductivity follows the Arrhenius law in the temperature ranges of 633–753 and 833–973 K, respectively. The ultrahigh thermal stability of dielectric permittivity is attributed to the weak coupling of polar clusters, the formation of diffuse phase transition, and the local phase transition of calcium-containing perovskite. The results provide new insights into the defects behavior and the modification way of re-entrant relaxor behavior.

Constructing Novel High-Performance Dipolar Glass Polymer Dielectrics by Polar Rigid/Flexible Side Chains.

Developing new polymer dielectrics with superior dielectric and energy storage properties is urgent to meet the demand for electronic devices in the field of microminiaturization or harsh environments. In this paper, two dipolar glass polymers based on polynorbornene main chain and flexible/rigid cyano side chain were synthesized by ring opening metathesis polymerization method: polymer PCEMT with flexible side chains and polymer PCPMT with rigid side chains. The backbone is built from two rigid five-membered rings, which not only avoids the narrow band gap caused by π-π conjugation of traditional aromatic main chains, but also maintains high thermal stability and high glass transition temperature (Tg). The introduced polar cyano groups on the side chain gave high dielectric constants (εr) for both polymers, where the εr of PCEMT and PCPMT reached 7.9 and 4.6 at room temperature and 1 kHz, respectively. Due to high polarization and high breakdown strength, the PCPMT obtains a maximum discharge energy density (Ud) of 4.47 J/cm3 at room temperature, which is 1.61 and 1.57 times of biaxially oriented polypropylene and polyimide (Kapton). The supernal Tg of 229 °C makes the energy storage performance of PCPMT almost unaffected at 100 °C. The charge-discharge efficiency (η) always keeps over 90% and an Ud of 5.2 J/cm3 at 480 MV/m is achieved, which is much better than Kapton (Ud = 1.77 J/cm3, η = 42.5%) under the same conditions. This work provides a new idea for preparing the high-performance polymer dielectrics via introducing rigid polar side chains.

Advancing with dipolar glass polymers

Advancing with dipolar glass polymers

Giant Polarization in Quasi‐Adiabatic Ferroelectric Na+ Electrolyte for Solid‐State Energy Harvesting and Storage

The advent of new solid‐state energy storage devices to tackle the electrical revolution requires the usage of nonlinear behavior leading to emergent phenomena. The ferroelectric analyzed herein belongs to a family of electrolytes that allow energy harvesting and storage as part of its self‐charging features when thermally activated. The Na2.99Ba0.005ClO electrolyte shows quasi‐adiabatic behavior with a continuous increase in polarization upon cycling, displaying almost no hysteresis. The maximum polarization obtained at a weak electric field is giant and similar to the remanent polarization. It depends on the temperature with a pyroelectric coefficient of 5.37 C m−2 °C−1 from −5 to 46 °C. The emergence occurs via negative resistance and capacitance. The glass transition is found to have its origins in the sharp depolarization at 46 – 48 °C. Above –10 °C, at ≈ –5 °C, another thermal anomaly may rely on the topologic characteristics of the A3–2xBaxClO (A = Li, Na, K) glass electrolytes enabling positive feedback of the current of electrons throughout the surface of the inner cell. The phenomena may pave the way toward a better understanding of dipolar nanodomain fragile glasses with exceptional ferroelectric characteristics to architect energy harvesting and storage devices based on multivalent thermally activated Na+‐ion‐ion electrolytes.

Mixology of MA1-x EA x PbI3 Hybrid Perovskites: Phase Transitions, Cation Dynamics, and Photoluminescence.

Mixing molecular cations in hybrid lead halide perovskites is a highly effective approach to enhance the stability and performance of optoelectronic devices based on these compounds. In this work, we prepare and study novel mixed 3D methylammonium (MA)-ethylammonium (EA) MA1-x EA x PbI3 (x < 0.4) hybrid perovskites. We use a suite of different techniques to determine the structural phase diagram, cation dynamics, and photoluminescence properties of these compounds. Upon introduction of EA, we observe a gradual lowering of the phase-transition temperatures, indicating stabilization of the cubic phase. For mixing levels higher than 30%, we obtain a complete suppression of the low-temperature phase transition and formation of a new tetragonal phase with a different symmetry. We use broad-band dielectric spectroscopy to study the dielectric response of the mixed compounds in an extensive frequency range, which allows us to distinguish and characterize three distinct dipolar relaxation processes related to the molecular cation dynamics. We observe that mixing increases the rotation barrier of the MA cations and tunes the dielectric permittivity values. For the highest mixing levels, we observe the signatures of the dipolar glass phase formation. Our findings are supported by density functional theory calculations. Our photoluminescence measurements reveal a small change of the band gap upon mixing, indicating the suitability of these compounds for optoelectronic applications.

High‐κ and High‐Temperature Dipolar Glass Polymers Based on Sulfonylated and Cyanolated Poly(Arylene Ether)s for Capacitive Energy Storage

AbstractHigh energy density, high temperature, and low loss dielectric polymers have drawn increasing attention in research owing to their potential applications in power electronic and pulsed power devices. In this study, a new class of organo‐soluble dipolar glass polymers (DGPs) are synthesized via polycondensation and post‐functionalization of poly(aryl ether)s (PAEs) based on phenolphthalin. Due to the nonplanar backbone structure, the strongly dipolar side groups (‐SO2CH3 and ‐CH2CH2CN) can easily rotate in these PAEs. As a result, desirable physical properties are obtained: high dielectric constant (4.4–5.6), high glass transition temperature (155–180 °C), good mechanical property, and low dielectric loss (dissipation factor &lt; 0.005). Among them, cyanolized poly(aryl ether nitrile) exhibit the highest discharged energy density of 8.6 J cm−3 at 650 MV m−1 and room temperature with a high discharged efficiency of 94.3%. At 100 °C, cyanolized poly(ether ether ketone) shows the highest discharged energy density of 7.3 J cm−3 at 600 MV m−1 with a discharged efficiency of 91%. Furthermore, these functionalized PAEs exhibit good mechanical toughness with a tensile strength at a break of 60‐120 MPa and elongation at a break of ≈5%. Based on their thermal, mechanical, and dielectric properties, these phenolphthalin‐based PAEs are promising for potential applications such as film capacitors.

Dipolar Glass Polymers for Capacitive Energy Storage at Room Temperatures and Elevated Temperatures

Dipolar Glass Polymers for Capacitive Energy Storage at Room Temperatures and Elevated Temperatures

Electrical Conductivity and Dielectric Relaxation in Ag1−xLixNbO3

The broadband electrical properties of Ag1−xLixNbO3 (ALNx) ceramics (x ≤ 0.1) together with AgNbO3 (AN) crystals were studied over a wide temperature interval of 20–800 K. For ALNx with x ≤ 0.05, a very diffused ferroelectric phase transition was observed. The position of the dielectric permittivity maximum in this phase transition is strongly frequency-dependent and is described well by the Vogel–Fulcher law. The freezing temperature decreases when the lithium concentration increases. Below the ferroelectric phase transition temperature, the dielectric dispersion is mainly caused by ferroelectric domain dynamics. Moreover, for ALN3 and ALN5 ceramics at very low temperatures (below 100 K), behavior typical of dipolar glasses is observed. At higher temperatures (above 650 K for ALN5), electrical conductivity effects become important. The DC conductivity increases with temperature according to the Arhenius law and the activation energy is highest in the antiferroelectric phase. Moreover, the activation energy is strongly dependent on the lithium concentration and it is greatest when x = 0.02.

Random-field critical scaling in a model of dipolar glass and relaxor ferroelectric behavior.

Heat-bath Monte Carlo simulations have been used to study a 12-state discretized Heisenberg model with a type of random field on simple cubic lattices of size 128×128×128. The 12 states correspond to the [110] directions of a cube. The model has the standard nonrandom two-spin exchange term with coupling energy J and a random field which consists of adding an energy h_{R} to two of the 12 spin states, chosen randomly and independently at each site. We report on the case h_{R}/J=3, which has a sharp phase transition at about T_{c}/J=1.40625. Below T_{c}, the model has long-range ferroelectric order oriented along one of the eight [111] directions. At T_{c}, the behavior of the peak in the structure factor, S(k), at small |k| is a straight line on a log-log plot, which gives the result η[over ¯]=1.214±0.014. The onset of orientational order below T_{c} is very rapid for this value of h_{R}. There are peaks in the specific heat and longitudinal susceptibility at T_{c}. Below T_{c} there is a strong correction to ordinary scaling, which is probably caused by the cubic anisotropy, which is a dangerous irrelevant variable.