Polar Cation Research Articles

An Approach to Estimate the Refractive Index and the Electronic Polarizability of the Ternary Ag2O-B2O3-TeO2 Glasses.

Each of the static properties such as refractive index (n0), cation ( ), and anion ( ) oxide polarizabilities for the ternary 30Ag2O⋅xB2O3⋅(70 - x)TeO2 (30AgBTe) glasses has been predicted theoretically from those of the binary 30Ag2O-70B2O3 and 30Ag2O-70TeO2 glasses. This can be done based on two assumptions: that each of these static properties (n0, , and ) can be considered as an additive property and that ternary 30AgBTe glasses can be treated as a mixture of two binary 30Ag2O-70B2O3 and 30Ag2O-70TeO2 glasses. In addition, n0 values for the ternary 30AgBTe glasses can be predicted in terms of and values for the ternary 30AgBTe glasses, and these later properties can be predicted from that of two binaries like as n0 at first stage. The n0 values obtained by using two methods are exactly the same for the corresponding compositions in the studied glasses, confirming the validity of the two assumptions and the procedure described in the present work. This conclusion is valid for the ternary glasses with a fixed content of either basic former/or modifier oxides for all compositions such as xPbO⋅(40 - x)Sb2O3⋅60B2O3 and 30Ag2O⋅xB2O3⋅(70 - x)TeO2 glasses, respectively.

Prediction of Nernst coefficient of S-containing compounds between fuel and ionic liquid phases in the extractive desulfurization using linear and supported vector machine (SVM) methods: QSPR-based machine learning

BackgroundThe presence of sulfur-containing compounds (SCCs) in the refinery streams has significant economic and environmental implications. Great attention has been focused on finding the proper green solvents like ionic liquids (ILs11Ionic liquids) with efficient extraction performance as a matter of concern of environmental issues. MethodsThe research aimed to develop a predictive model using QSPR to forecast the partition coefficient of dibenzothiophene by ILs from n-dodecane. Utilizing a dataset of 54 ILs and their partition coefficients for DBT, the study employed two methods to optimize ILs structures and compared linear (GA-MLR) and non-linear (LS-SVM) models, with non-linear models showing higher accuracy. After initial modeling and assessing the primary dataset of 54 ILs, yielding an R2 parameter of 0.39 for the test set, the dataset was divided into smaller clusters for further analysis. Three additional clusters were investigated. The second cluster comprised 14 ILs with identical cations and varying anions, modeled with two descriptors. The third cluster, consisting of 21 ILs with imidazolium cations and diverse anions, was modeled with three descriptors. Lastly, the fourth cluster, comprising 26 ILs with different cations but the same anion, was also modeled with three descriptors. Significant findingsThe MLR model yielded R2 values of 0.98, 0.85, and 0.93 for the test sets of the second, third, and fourth clusters respectively. Effective descriptors, including cation polarizability and alkyl branch length, were examined for their impact on partition coefficient and desulfurization efficiency. This research aids in enhancing EDS processes with ILs, advancing more efficient desulfurization technologies.

Ultrahigh Energy Storage in (Ag,Sm)(Nb,Ta)O3 Ceramics with a Stable Antiferroelectric Phase, Low Domain-Switching Barriers, and a High Breakdown Strength.

AgNbO3 (AN) antiferroelectrics (AFEs) are regarded as a promising candidate for high-property dielectric capacitors on account of their high maximum polarization, double polarization-electric field (P-E) loop characteristics, and environmental friendliness. However, high remnant polarization (Pr) and large polarization hysteresis loss from room-temperature ferrielectric behavior of AN and low breakdown strength (Eb) cause small recoverable energy density (Wrec) and efficiency (η). To solve these issues, herein, we have designed Sm3+ and Ta5+ co-doped AgNbO3. The addition of Sm3+ and Ta5+ reduces the tolerance factor, polarizability of B-site cations, and domain-switching barriers, enhancing AFE phase stability and decreasing hysteresis loss. Meanwhile, adding Sm3+ and Ta5+ leads to decreased grain sizes, increased band gap, and reduced leakage current, all contributing to increased Eb. As a benefit from the above synergistic effects, a high Wrec of 7.24 J/cm3, η of 72.55%, power density of 173.73 MW/cm3, and quick discharge rate of 18.4 ns, surpassing those of many lead-free ceramics, are obtained in the (Ag0.91Sm0.03)(Nb0.85Ta0.15)O3 ceramic. Finite element simulations for the breakdown path and transmission electron microscopy measurements of domains verify the rationality of the design strategy.

Influence of crystal system, bond valence and ionic polarizability on the microwave dielectric properties of BaIn2O4 ceramic

BaIn2O4 ceramics with the monoclinic crystal system of the P21/c space group were synthesized using a solid-state reaction method. The sample sintered at 1250 °C exhibits a relative density (94.3 %) and the following microwave dielectric properties: εr = 16.3, Q × f = 49,500 GHz, τf = −73.1 ppm/°C. The bond valence results shows that the deviation of permittivity (24.9 %) between the experimental (εr = 16.3) and calculated values (εrC-M = 13.05) obtained using the Clausius−Mosotti equation may be ascribed to the rattling effect of Ba2+ and In3+. Compared with orthorhombic CaIn2O4 and SrIn2O4 ceramics, BaIn2O4 ceramics have lower Q × f values possibly because of the intrinsic loss caused by nonharmonic lattice vibration. The Edc value (0.43 eV) of BaIn2O4 demonstrates that the defects are caused by the single ionized oxygen vacancies. The intrinsic εr (14.7) and Q × f (105,600 GHz) values of the BaIn2O4 ceramic was inferred through infrared reflectivity spectroscopy. All results demonstrate that the dielectric properties are affected not only by density, ionic polarizability, and rattling effect of cations, but also by the crystal system, and particularly the intrinsic factors.

Hydroxy-Functionalized Ionic Liquids under Pressure: The Influence on Hydrogen Bonding between Ions of Opposite and Like Charges.

Hydroxy functionalization of cations in ionic liquids (ILs) can lead to formation of hydrogen bonds between their OH groups, resulting in so-called (c-c) H-bonds. Thereby, the (c-c) H-bonds compete with regular H-bonds (c-a) between the OH groups and the anions. Polarizable cations, weakly interacting anions, and long alkyl chains at the cation support the propensity for the formation of (c-c) H-bonds. At low temperatures, the equilibrium between (c-c) and (c-a) H-bonds is strongly shifted in favor of the cation-cation interaction. Herein, we clarify the pressure dependence on (c-c) and (c-a) H-bond distributions in the IL 1-(2-hydroxyethyl)-3-methylimidazolium hexafluorophosphate [HOC2C1Im][PF6], in mixtures of [HOC2C1Im][PF6] with the nonhydroxy-functionalized IL 1-propyl-3-methylimidazolium hexafluorophosphate [C3C1Im][PF6] and in [HOC2C1Im][PF6] including trace amounts of water. The infrared (IR) spectra provide clear evidence that the (c-c) H-bonds diminish with increasing pressure in favor of the (c-a) H-bonds. Adding trace amounts of water results in enhanced (c-c) clustering due to cooperative effects. At ambient pressure, the water molecules are involved in the (c-c) H-bond motifs. Increasing pressure leads to squeezing them out of H-bond clusters, finally resulting in demixing of water and the IL at the microscopic level.

Refractive index dispersion prediction for garnets (A3B2C3X12)

AbstractA model for the refractive index dispersion of garnets was developed by extension of a model for garnet refractive indices at 589 nm wavelength. The cation and anion polarizabilities in garnets were determined as a function of wavelength from dispersion data, and fit to Sellmeier relations. Dispersion predictions were compared to measurements of refractive index between 400 and 5500 nm for 35 garnet compositions. The median prediction error was 0.5% with a maximum error < 4.4%. Sources of error and applications of the predictive method are discussed.

Structural, thermal, surface, and electrical properties of Bi2O3 ceramics co–doped with Er–Ho–Tb rare earths

Face–centered cubic–Bi2O3 (δ–phase) material is a better ion conductor when compared to other types of solid electrolytes that have been declared in the literature due to its anion–defective crystal configuration, and hence it can be a promising solid electrolyte choice for intermediate temperature SOFC applications. In this research, Er–Ho–Tb co–doped Bi2O3 compounds were successfully synthesized by the solid–state reaction method and characterized using the XRD, TG & DTA, FPPT, and FE–SEM techniques. Apart from sample 4Er4Ho4Tb, each sample became stable with a cubic δ–phase at room temperature, according to XRD patterns. The DTA curves revealed no exothermic or endothermic peaks, implying a phase change in the constant heating cycle. The conductivity of Ho–rich compositions was higher than that of others, confirming the impact of cation polarizability on conductivity. In addition, at 700 °C, the sample 4Er8Ho4Tb with 1:2:1 content ratios had the highest conductivity of 0.29 S/cm. The porosity on the grain boundaries increased with doping, leading to higher grain boundary resistance, which could be responsible for the conductivity drop.

Machine Learning Approach for the Material Search of Fluoride-Ion Conductors

Fluoride-ion conductors are key materials for realizing all-solid-state fluoride batteries, which theoretically exhibit high energy densities of 4,400 Wh L–1 using Cu cathode and LaF3 anode1-2. To date, a high fluoride-ion conductivity has been reported for limited compounds, such as fluorite-type MSnF4 (M = Pb or Ba)3, tysonite-type Ln 1−x AEx F3−x (Ln = La–Sm, AE = Ca, Sr, or Ba)4, and ASn2F5 (A = Na, K, Rb, or NH4)5. However, the conductivities of these structures can be improved only to a limited extent, necessitating the search for novel phases in multielement systems6. Material search in a multielement system is cost- and effort-intensive due to the extremely large compositional space. In this study, we used regression learning of the ionic conductivities based on compositional descriptors aiming to accelerate the material search for fluoride-ion conductors. Training data on ionic conductivity at room temperature for 317 crystalline or amorphous fluorides were collected from the literature. Descriptors were prepared using only compositional properties (e.g., polarizability, ionic radius, and electronegativity). Regression learning using lasso, ridge, elastic net, support vector machine, and random forest were performed. Fig. 1 shows the correlation between the measured and predicted conductivities from random forest regression. Random forest yields the highest R 2 values of 0.96 and 0.85 for the training and test data, respectively. The highest permutation importance was given for the descriptor of the cation polarizability. Highly polarizable cations such as Bi3+, Sb3+, Pb2+, Sn2+, Tl+, Ag+, Cs+, and Rb+ are essential for achieving a high fluoride-ion conductivity. Moreover, the mean of melting point of metal fluorides and mean of M–F binding energy exhibit high importance scores, suggesting that a weak interaction between the metal cation and fluoride ion is preferred for fluoride-ion conduction. The predictive performance was experimentally verified, and the correlation between the measured and predicted ionic conductivities of the BaF2–SnF2–LaF3 (or KF) pseudo-ternary system was demonstrated. The ionic conductivities of the experimentally obtained samples, as illustrated as green circles in Fig.1, suitably match the predicted values. During experimental verification, new tysonite-type Ba0.2Sn0.8F2 was identified in the SnF2-rich composition region, where a high ionic conductivity was predicted. Rietveld analysis was performed using synchrotron X-ray diffraction (SXRD) data. Refinement was conducted with space group of P63/mmc. Barium and tin simultaneously occupy the 4e site with occupancies of 0.2 and 0.8, respectively, and form a hexagonal close-packed structure. Fluoride ions occupy two distinct sites, 2b and 4f, which adopt three- and four-fold coordination by M 2+ ions (M = Ba0.2Sn0.8), respectively. The occupancies of the fluoride ions at the 2b and 4f sites are 0.626 and 0.687, respectively, suggesting that numerous vacancies are randomly distributed at both sites, which is a unique feature of Ba0.2Sn0.8F2. The composition-based model for the prediction of the ionic conductivity enables to ascertain the compositional regions with high predicted ionic conductivities; consequently, it reduces the cost of material search and accelerates the discovery of fast fluoride-ion-conducting materials.Acknowledgement: This presentation is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).Reference: (1) M. A. Reddy, et al., J. Mater. Chem., 21, 17059 (2011). (2) F. Gschwind, et al., J. Fluorine Chem., 182, 76 (2016). (3) G. Denes, et al., Solid State Ionics, 13 , 213 (1984). (4) C. Rongeat, et al., ACS Appl. Mater. Inter. 6 , 2103 (2014). (5) J. P. Battut, et al., Solid State Ionics, 22 , 247 (1987). (6) K. Suzuki, et al., J. Mater. Chem. A, 8 , 11582 (2020).Figure 1. Predicted versus measured logarithm of the ionic conductivity. Red, blue, and green circles correspond to the training, test, and experimental data of the newly synthesized compounds. The black line represents the ideal line, i.e., where the predicted and measured conductivities are equal. Figure 1

Correlation between Ionic Radii and Cation Polarizability (Review)

The polarizability approach in the glasses has been detailed studied by V. Dimitrov and T. Komatsu. Here a review is taken on the basics of their literature values classifying on number of ions and there average values of cation polarizability given by Kordes and Pauling on the basis of a couple sets of free- ion polarizabilities. Key Words: Cation, Ionic radii, Cation polarizability.

Impacts of Exciton Binding Energy and Dielectric Confinement of Layered Lead Halide Perovskites on Carrier Relaxation and Exciton Phonon Interactions.

This work highlights the significance of dielectric confinements and exciton binding energy of hybrid layered perovskites (LPs) in controlling the carrier relaxation dynamics of LPs for designing efficient optoelectronic devices. The polarizability of organic spacer cations in LPs modulates the carrier-phonon and carrier-carrier interactions, which eventually control the carrier relaxation dynamics. Here, we have varied the alkyl-ammonium chain length in the LPs to change the dielectric confinement, and the first-principles calculations reveal that the long-chain organic spacer experiences stronger dielectric confinement in comparison to short-chain organic spacer cation-based LPs. Transient absorption spectroscopic analysis suggests that the larger dielectric confinement and higher exciton binding energy exhibit faster carrier relaxation dynamics. The enhanced exciton-phonon interaction leads to faster carrier relaxation dynamics. The much softer phonon modes are responsible for the higher up-conversion of acoustic modes to optical modes, which leads to slower carrier relaxation dynamics in n-butylamine (BA) based LPs.

Effect of sintering temperature on impedance and EMI shielding of carbon modified CoFe2O4 nanofibers via electrospinning

The electrospinning technique is employed for the synthesized cobalt ferrite/carbon nanofibers, utilizing iso-propanol as the solvent. The nanofibers prepared are subjected to sintering at three different temperatures. A comprehensive analysis is carried out on the structural, morphological, dielectric, impedance, and electromagnetic shielding effectiveness within the X-band frequency range (8.2–12.4 GHz). The application of the Debye-Scherer formula yielded an estimated crystallite size of 22 nm. The electrical response of cobalt ferrite/carbon nanofibers pellet is characterized by employing impedance spectroscopy. Variations in impedance plane plots are discussed based on frequency dependent relaxation time modulations. The impact of sintering temperature is observed in terms of increased impedance values and modifications in the conduction mechanism. These changes are contributed to distinct hopping carriers’ linkages between Fe3+-Fe2+ and Co3+-Co2+ ions. Dielectric studies are elucidated considering cation polarizability, colossal resistivity, and tangent loss. This study revealed notable characteristics of CoFe2O4/C nanofibers, including colossal resistivity (8.45 × 108 Ωcm), a dielectric constant of 22, and colossal tangent loss. The CoFe2O4/C nanofibers exhibit a characteristic electromagnetic interference (EMI) shielding performance of 30–35 dB. This remarkable shielding performance is observed in nanofibers with a 3 mm thickness, specifically in sample S1 that underwent sintering at a low temperature. The shielding effectiveness is demonstrated within the X-band frequency range.

MnO2 doping stabilized antiferroelectric P phase and underlying physical mechanism in NaNbO3-SrTiO3 lead-free ceramics

The incorporation of a few amount of MnO2 into 0.88NaNbO3-0.12SrTiO3 lead-free ceramics was found to effectively stabilize the antiferroelectric orthorhombic P phase before its transition into antiferroelectric orthorhombic R phase, consequently featuring completely reversible electric field-induced antiferroelectric-ferroelectric phase transition. Not only reproducible double polarization hysteresis loops but also repeated sprout-like strain-field curves ensure great application potentials in large-displacement lead-free actuators owing to both large repeatedly-utilized strains of ∼0.33% and low driving field of ∼11 kV/mm. Combined results of XPS, Raman spectroscopy and dielectric properties indicate that the stabilized antiferroelectric P phase was closely related to the reduced B-site cation polarizability and oxygen vacancy concentration, while a slight change in antiferrodistortive degree would discourage the P-R phase transition. These results indicate that ionic doping is an alternative method to alter the antiferroelectric P phase stability of NaNbO3-based lead-free ceramics by synergistically considering the influencing factors of phase and crystal structure stability.

Introducing highly polarizable cation in M-N-C type catalysts to boost their oxygen reduction reaction performance

The metal-nitrogen-carbon (M-N-C) type oxygen reduction reaction (ORR) catalysts are promising for hydroxide exchange membrane fuel cells, but catalysts with further improved performance are challenging. Here, we report the efficient improvement of the ORR activity of M-N-C catalysts by employing highly polarizable metal cation Ag+. Ag, Fe single atomic sites embedded in concave nitrogen doped carbon (Ag1Fe1/CNC) is successfully synthesized and shows high performance towards ORR, indicating by both the ultra-high half-wave potential of 0.917 V and membrane electrolyte assembly performance of peak power density up to 1.26 W cm−2. The binding energy of the ORR intermediates on the highly polarizable Ag site in Ag1Fe1/CNC was significantly tuned by the adjacent Fe site by more than 0.2 eV, and thus leading to a low theoretical ORR overpotential of only 0.398 V. The employment of the highly polarizable metal cation brings a novel and efficient approach to construct highly active catalysts.

Bond Polarizability as a Probe of Local Crystal Fields in Hybrid Lead-Halide Perovskites.

A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell. We measure the average polarizability of the C/N-H bond stretching mode by means of infrared spectroscopy, which allows us to deduce the character of the motion of the cation molecule, find the magnitude of the local crystal field, and place an estimate on the strength of the hydrogen bond between the hydrogen and halide atoms. Our results pave the way for understanding electric fields in lead-halide perovskites using infrared bond spectroscopy.

1D Diisopropylammonium Lead Iodide Perovskite Shows Exceptional Optical Stability and Third‐Order Nonlinearity

AbstractLow‐dimensional lead‐halide perovskites show wide structural and compositional diversity. Multiple functionalities can be introduced in these materials for diverse linear and nonlinear optical applications. Nonlinear optical (NLO) processes depend on material polarizability, crystal symmetry, and processibility. The flexibility of choosing organic cations in lead‐halide perovskites provides an opportunity for enhanced NLO responses by enhancing the overall system polarizability. A highly polarizable diisopropylammonium [Dipa; ((CH3)2CH)2NH2+] is used as an A‐site cation to synthesize one‐dimensional (1D) lead‐iodide (DipaPbI3) perovskite single crystals and the third‐harmonic generation (THG) in the excitation wavelength range of 1200–1600 nm is explored. DipaPbI3 single crystals exhibit exceptionally efficient resonance‐enhanced THG, amazing optical stability, and a high polarization ratio due to enhanced bulk‐polarization. The THG efficiency (χ(3) ≈ 4 × 10−18 m2 V−2) and laser‐induced damage threshold (LIDT, 144 GW cm−2) are an order of magnitude higher than the reported perovskites explored as THG materials. Density functional theory calculations show a significantly higher polarizability for Dipa cation, asserting the influence of the cation polarizability on the NLO efficiency of the perovskite. The stability of these single crystals in ambient conditions for an extended period adds to their potential for commercial application in the near future.

Role of organic cations in tuning the exciton binding energy of 2D lead iodide perovskite derivatives

Control over the exciton binding energy (Eb) in two-dimensional (2D) perovskites can enable their application in a broad range of optoelectronic technologies. To investigate the effects of organic cations on the excitonic properties of 2D perovskites, films of lead iodide hybrids basing on four structurally similar cations of phenylethylammonium (PEA), 4-florophenylethylammonium (FPEA), 4-chlorophenylethylammonium (ClPEA) and 4-bromophenylethylammonium (BrPEA) were prepared and their optical properties were characterized. Results show that both the perovskite layer distortion and exciton absorption/emission peak do not vary too much by the substitution of halogen atom in the para H of phenylethyl cation. Further examination of the temperature-dependent exciton emission properties reveals that the thermal activation energy Ea, which can also be regarded as exciton binding energy in our work, can be tuned over ca. 170 meV within the set of hybrids. It is found that exciton binding energy is sensitive to the identity of organic cations and to the resulting PbI6 octahedron distortion. Among the compounds considered, FPEA based perovskite has the biggest PbI6 octahedron distortion and the largest calculated Ea of 330 meV, while the Br-PEA based perovskite shows a smaller octahedron distortion and the lowest calculated Ea. We believe that an enhanced polarizability of organic cations may be responsible for the observed decrease in octahedra distortion and Ea for the p-halophenylethylammonium lead iodide perovskite derivatives.

A Polar Tetragonal Tungsten Bronze with Colossal Second-Harmonic Generation.

A polar tetragonal tungsten bronze, Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 (□: vacancies), has been successfully synthesized by a high temperature solid-state reaction. Single crystal and powder X-ray diffraction indicate that the structure of Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 crystallizing in the noncentrosymmetric (NCS) space group, P4bm, consists of 3D framework with highly distorted NbO6 , LiO9 , PbO12 , and (Pb/K)O15 polyhedra. While NCS Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 undergoes a reversible phase transition between polar (P4bm) and nonpolar (P4/mbm) structure at around 460 °C, the material decomposes to centrosymmetric Pb1.45 K3.56 Li3.54 Nb10 O30 (P4/mbm) once heated to 1200 °C. Powder second-harmonic generation (SHG) measurements with 1064nm radiation indicate that Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 exhibits a giant phase-matchable SHG intensity of ≈71.5 times that of KH2 PO4 , which is the strongest intensity in the visible range among all nonlinear optical materials reported to date. The observed colossal SHG should be attributable to the synergistic effect of dipole moments from the well-aligned NbO6 octahedra, the constituting distortive channels with vacancies, and highly polarizable cations.

Thermal properties of CaO and SrO and their B1-B2 phase boundaries: Validity of the quasi-harmonic approximation

In this paper, we will further confirm that the validity range of the quasi-harmonic approximation (QHA) can be significantly extended by explicitly calculating the Helmholtz free energy over an appropriate volume range. As in the case of MgO, we performed accurate QHA calculations of the thermal properties of the B1 phase of CaO and SrO over a wide temperature range, as well as their B1-B2 phase boundaries in the pressure–temperature space. This finding contradicts a recent conclusion that the QHA is inadequate for CaO, and it is therefore expected to fail for other alkaline-earth oxides containing more polarizable cations. Moreover, the validity range of the QHA is found to be consistent with the bond ionicity in MgO, CaO and SrO.

Ultrahigh energy density and excellent discharge properties in Ce4+ and Ta5+ co-modified AgNbO3 relaxor antiferroelectric ceramics via multiple design strategies

Silver niobate (AgNbO3) has been recently regarded as one of the best candidates for developing high-performance dielectric capacitors on account of its large maximum polarization and near-zero remnant polarization, but its room-temperature ferrielectric (FIE) behavior and large electric hysteresis impede further improvement of energy storage properties. In order to solve this issue, herein, we design Ce4+ and Ta5+ co-modified (Ag0.96Ce0.01)(Nb1-xTax)O3 relaxor antiferroelectric (AFE) ceramics. The introduction of Ce4+ and Ta5+ decreases the tolerance factor, reduces the B-site cation polarizability, and enhances A- and B- site cation disorder, leading to suppressed FIE characteristic, improved AFE stability, and enhanced relaxor degree. Besides, the co-doping strategy causes the decrease of the grain size, and the experimental results and finite element simulations both indicate that this is fairly effect on the improvement of the breakdown strength. Consequently, an ultrahigh recoverable energy density of 7.37 J/cm3, which far exceeds those of the latest AgNbO3-based ceramics, and a large efficiency of 75.66% are simultaneously achieved in (Ag0.96Ce0.01)(Nb0.7Ta0.3)O3 ceramics. More encouragingly, the ceramic exhibits excellent actual discharge capacity with ultrafast discharge time of 23 ns and ultrahigh power density of 294.28 MW/cm3, which outperforms many recently reported lead-free dielectric ceramics, and the discharge properties are fairly stable during a wide temperature range of 20–180 °C. This work sheds light on designing and developing high-performance lead-free dielectric capacitors applicable in harsh environment.

Ion-Specific Antipolyelectrolyte Effect on the Swelling Behavior of Polyzwitterionic Layers

In this study, we systematically investigate the interactions between mobile ions generated from added salts and immobile charges within a sulfobetaine-based polyzwitterionic film in the presence of five salts (KCl, KBr, KSCN, LiCl, and CsCl). The sulfobetaine groups contain quaternary alkylammonium and sulfonate groups, giving the positive and negative charges. The swelling of the zwitterionic film in the presence of different salts is compared with the swelling behavior of a polycationic or polyanionic film containing the same charged groups. For such a comparative study, we design cross-linked terpolymer films with similar thicknesses, cross-link densities, and charge fractions, but with varying charged moieties. While the addition of salt in general leads to a collapse of both cationic and anionic films, the presence of specific types of mobile anions (Cl-, Br-, and SCN-) considerably influences the swelling behavior of polycationic films. We attribute this observation to a different degree of ion-pair formations between the different types of anionic counterions and the immobile cationic quaternary alkylammonium groups in the films where highly polarizable counterions such as SCN- lead to a high degree of ion pairing and less polarizable counterions, such as Cl-, cause a low degree of ion pairing. Conversely, we do not observe any substantial effect of varying the type of cationic counterions (K+, Li+, and Cs+), which we assign to the lack of ion pairing between the weakly polarizable cations and the immobile anionic sulfonate groups in the films. In addition, we observe that the zwitterionic films swell with increasing ionic strength and the degree of swelling is anion dependent, which is in agreement with previous reports on the "antipolyelectrolyte effect". Herein, we explain this ion-specific swelling behavior with the different cation and anion abilities to form ion pairs with quaternary alkylammonium and sulfonate in the sulfobetaine groups.