Activation Energy For Conduction Research Articles

Enhanced dielectric and ferroelectric properties near the morphotropic phase boundary in BNBT-BSN ceramics prepared by the solid-state combustion technique

The effect of firing temperatures on the phase structure, microstructure, and electrical properties of 0.99Bi0.47Na0.47Ba0.06TiO3-0.01BaSn0.70Nb0.24O3 (abbreviated as BNBT-BSN) lead-free ceramics fabricated by the solid-state combustion technique, with glycine used as the fuel, were investigated. All BNBT-BSN samples were calcined at temperatures ranging from 750 to 850 °C for 1 to 4 h and sintered at temperatures from 1100 to 1200 °C for 2 h. A pure perovskite structure was obtained after calcination at 800 °C for 2 h. The X-ray diffraction (XRD) patterns showed the coexistence of rhombohedral and tetragonal phases in all ceramics. The average grain size tended to increase with rising sintering temperatures. The optimal condition for fabricating BNBT-BSN ceramics with a morphotropic phase boundary (MPB) was observed at a sintering temperature of 1175 °C for 2 h, where the material exhibited the highest measured density (5.50 g/cm3), maximum dielectric constant at Tm (ɛm = 6513), maximum polarization (Pmax = 42.21 µC/cm2), the largest bulk resistivity (ρ = 1.70 × 104) and the highest activation energy of conduction (Ea = 1.52 eV). These features suggest that this ceramic is a suitable material for applications in actuators, transducers, and high-performance capacitors.

New approaches to enhancing the performance of ceria-based electrolytes: A study on the microstructure, ionic conductivity, and mechanical properties of Cu-Gd Co-doping

This study addresses the performance limitations of traditional SOFC electrolytes at intermediate temperatures by synthesizing Cu-Gd co-doped ceria-based electrolytes, Gd0.1Ce0.9-xCuxO2-δ (x=0.04, 0.07, 0.10), using the citric acid-EDTA combustion method. This aims to enhance the ionic conductivity and mechanical stability of solid oxide fuel cells (SOFC) at intermediate to high temperatures. XRD and Rietveld refinement indicate that the introduction of Cu ions has not disrupted the original single-phase cubic fluorite structure of Gd0.1Ce0.9O1.95. SEM and EDS analyses indicate that Cu incorporation increased grain size and improved elemental distribution. XPS analysis confirmed that Cu-Gd co-doping increased the concentration of oxygen vacancies and hindered the reduction of Ce4+. Density functional theory calculations suggest that Cu addition effectively suppressed electronic conductivity in the Gd0.1Ce0.9O1.95 system and significantly lowered the formation, binding, and migration energy barriers of oxygen vacancies. EIS analysis revealed that the sample with x=0.07 had a 20 % reduction in ionic conduction activation energy and exhibited the highest ionic conductivity of 0.013 S/cm at 750°C, two orders of magnitude higher than that of singly doped Gd0.1Ce0.9O1.95. This enhancement is attributed to a certain extent to the scavenging rate of Gd0.1Ce0.83Cu0.07O2-δ reaching 22.30, while the blockage factor has decreased by nearly 60 % compared to Gd0.1Ce0.9O1.95. Additionally, Cu incorporation resulted in a nearly tenfold decrease in the extent of oxygen vacancy concentration loss in the space charge layer, reducing the potential from 0.41 V (Gd0.1Ce0.9O1.95) to 0.34 V (Gd0.1Ce0.83Cu0.07O2-δ), which benefits the concentration of oxygen vacancies in the space charge layer. Moreover, in terms of mechanical properties, compared to singly doped samples, co-doped samples exhibited increases of approximately 20.2 % in Vickers hardness, 78.3 % in fracture toughness, and 54.8 % in flexural strength. Thus, Cu-Gd co-doping can be considered an effective strategy for enhancing the performance of ceria-based electrolytes in IT-SOFCs.

Experimental and Theoretical Investigation of Anisotropic Proton Conduction in Two-Dimensional Metal-Organic Frameworks.

Two-dimensional (2D) materials are known for their potential to exhibit anisotropic transport properties due to their layered structures. However, the anisotropic ion conduction of 2D metal-organic frameworks (MOFs) has been rarely explored. In this study, we investigated the anisotropic proton conduction along the in-plane and stacking directions of two analogs of undulating 2D MOFs: [Mn(salen)]2[Pt(CN)4]·H2O (MnPt) and [Mn(salen)]2[PtI2(CN)4]·H2O (MnPtI). This investigation was conducted using both experimental methods, involving single crystals, and theoretical calculations. Compared to the relatively isotropic proton conduction of MnPt at 85 °C and 95% relative humidity (RH), with a stacking direction conductivity (σstacking) of 1.8 × 10-5 S/cm, which is approximately 2.9 times the in-plane conductivity (σin-plane), MnPtI exhibited highly anisotropic proton conduction. The σstacking of MnPtI under the same conditions (85 °C, 95% RH) was 1.5 × 10-4 S/cm, which is 83 times higher than its σin-plane. Additionally, the activation energy for proton conduction in MnPtI ranged from 0.65 to 0.73 eV, which is higher than the 0.48 eV observed for MnPt. Theoretical calculations confirmed that slight differences in local structures, including node distortions between MnPt and MnPtI, significantly influenced the activation energies for water migration. This was attributed to the formation of hydrogen bonds between layers and water molecules.

Electroactive ferrocene-based ionic liquids: transport and electrochemical properties of their acetonitrile solutions

The increasing global demand for energy stimulates the development of advanced energy storage and conversion technologies. Modification of electrolyte with redox-active additives is a promising way to enhance the electrochemical performance of energy storage devices. In this work new electroactive ferrocene-based ionic liquids (Fc-ILs) (N-methyl-N-(ferrocenylmethyl)piperidinium bis(trifluoromethanesulfonyl)imide [PipFcMe][NTf2], N-methyl-N-(ferrocenylmethyl)pyrrolidinium bis(trifluoromethanesulfonyl)imide [PyrFcMe][NTf2], N-ethyl-N-(ferrocenylmethyl)pyrrolidinium bis(trifluoromethanesulfonyl)imide [PyrFcEt][NTf2]) were synthesized. The structure of the Fc-ILs was confirmed by NMR and XRD. [PipFcMe][NTf2] and [PyrFcMe][NTf2] demonstrated nearly similar crystal structures consisting of cation and anion columns, while alternating cation and anion layers are stacked in the [PyrFcEt][NTf2] crystal. The effects of the Fc-IL mole fraction and temperature on the transport properties of the acetonitrile solutions of the Fc-ILs have been established. The highest electrical conductivities of the [PipFcMe][NTf2], [PyrFcEt][NTf2] and [PyrFcMe][NTf2] solutions calculated using the Casteel-Amis equation were, respectively, 38.06 ± 0.63, 40.34 ± 0.93 and 41.09 ± 0.58 mS/cm at 348.15 K. The activation energies of conductivity were calculated using the Arrhenius and Vogel-Fulcher-Tamman approaches. The Fc-ILs demonstrated a high electrochemical stability range up to 4.67 V. The introduction of electron-withdrawing substituents into the cyclopentadienyl ring of Fc-ILs shifted the half-wave potential to the positive direction. The diffusion coefficients were calculated using the Randles–Ševčík equation for a quasi-reversible process.

Prediction of Li-ion conductivity in Ca and Si co-doped LiZr2(PO4)3 using a denoising autoencoder for experimental data

All-solid-state batteries composed of inorganic materials are in high demand as power sources for electric vehicles owing to their improved safety, energy density, and overall lifespan. However, the low ionic conductivity of inorganic solid electrolytes has limited the performance and adoption of inorganic all-solid-state batteries. The solid electrolyte LiZr2(PO4)3 has attracted attention owing to its high Li-ion conductivity. The ionic conductivity of LiZr2(PO4)3 changes with the crystalline phase obtained, which varies based on composition control through elemental substitution and process conditions such as sintering temperature. Traditionally, optimizing such parameters and understanding their relationship to physical properties have relied on researcher experience and intuition. However, a recent use of a materials informatics approach utilizing machine learning shows promise for more efficient property optimization. This study proposes a deep learning model to correlate powder X-ray diffraction (XRD) profiles with the activation energy (Ea) for Li-ion conduction, thereby enhancing the interpretability of the measurement data. XRD profiles, which contain information on crystal structure, lattice strain, and particle size, were used as-is (i.e., without preprocessing) in the deep learning model. An attention mechanism was introduced to the deep learning model that focuses on XRD crystal-structure information and visualization of important factors embedded in the XRD profiles. The highlighted areas in the output of this model successfully predict LiZr2(PO4)3 phases with low Ea (high Li conductivity) and high Ea (low Li conductivity). Moving forward, this deep learning model can offer new insights to materials researchers, potentially contributing to the discovery of new solid electrolyte materials.

Y, Yb, and Gd tri-doping on B-site of Ba(Zr, Ce)O3-δ with improved proton conduction performance

Perovskite-type proton conducting electrolytes are garnering significant attention due to its key role in protonic ceramic electrochemical cells (PCEC) and its application in hydrogen sensors (HS) used for metal melt measurements. Developing high proton conduction perovskite materials with good chemical stability is always a worldwide research focus. In this paper, Y, Yb and Gd triple-doping on B-site of BaCeO3-BaZrO3 solid solution were carried out to investigate the effect of gadolinium doping on the performance of protonic conducting electrolytes. BaZr0.1Ce0.7(Y0.5Yb0.5)0.2-xGdxO3-δ (x = 0, 0.1, 0.15 and 0.2), which were also referred as BZCYYbGdx (x = 0, 10, 15 and 20), were synthesized by solid-state reaction at 1600 °C for 10 h. It is found that BZCYYbGd15 has the highest proton conductivity and proton transfer number among the four prepared materials. The proton mobility of BZCYYbGd15 is 4.06 × 10−6 cm2/(Vꞏs) at 800 °C, which increases with an increased temperature. Its proton transfer number is higher than 0.9 at 500 °C under the atmosphere of PH2O = 0.018 atm. A moderate doping of gadolinium increases the temperature threshold for proton conduction. Proton, oxygen vacancy, electron hole and total conductivity activation energies of BZCYYbGd15 under the wet atmosphere are found to be 0.74, 1.58, 1.41 and 0.92 eV, respectively. Furthermore, the chemical stability of pellets is improved after gadolinium doping. This study provides a reference value for future research on high proton conduction electrolytes.

The Electrical Conductivity Mechanisms and Dielectric Properties of Multiphase Co-synthesized CuV2O6–MnV2O6

AbstractMany research studies on photodegradation, energy storage applications, and biosensing have focused on single and mixed Cu and Mn divanadates (MV2O6, M2+ = Cu2+ and/or Mn2+). In this work, MV2O6 was synthesized, and its electrical conductivity and dielectric properties were studied. The electrical and dielectric properties were investigated in a frequency range of 0.1-300 kHz and a temperature range of 298 K to 573 K. The results indicate that the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor, and loss tangent of the investigated materials increase with temperature, which support the contribution of grains and grain boundaries to the electrical properties. The materials exhibit non-Debye type relaxation, as indicated by the progression of the relaxation frequency. As frequency increases, the activation energy of AC conduction decreases, indicating that hopping conduction is the dominant mechanism. In all samples, the DC conduction activation energy is higher than the AC conduction activation energy. The circuit model was used to estimate the relaxation times. The results revealed remarkable dielectric characteristics, notably higher dielectric loss tangent values at frequencies below 1 kHz. Consequently, these materials can be used as electromagnetic attenuation absorbers. Graphical Abstract

Impedance Spectroscopy of Lanthanum-Doped (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 Ceramics

This study examines the effects of La3+ doping on (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3(PBZT) ceramics, which were synthesized using the conventional solid-state reaction method. X-ray diffraction analysis confirmed that the PBZT structure, including PBZT doped with La3+ at concentrations x = 1 at.% and x = 2 at.%, exhibited a rhombohedral (R3c) space group, while higher doping levels of x = 3 at.% and x = 4 at.% led to a dominant cubic (Pm-3m) phase with approximately 30% of a remnant rhombohedral component. Scanning electron microscopy (SEM, JEOL JSM-7100F TTL LV, Jeol Ltd., Tokyo, Japan) and energy dispersive X-ray spectroscopy (EDS) were utilized to investigate the structure and morphology of these ceramics. The findings indicated that the chemical composition of the ceramic samples closely corresponded to the initial stoichiometry of the ceramic powder. An increase in the amount of lanthanum results in a decrease in the average grain size of the ceramics. The electrical properties were further evaluated using complex impedance spectroscopy (IS) over a range of temperatures and frequencies, as well as temperature dependence of DC conductivity. The similarity in the changes in activation energy for DC conductivity and grain boundary conductivity, caused by lanthanum ion modification, allows for the conclusion that grain boundaries are the primary microstructural element responsible for conductivity in these materials.

Relaxation dynamics and conductivity in poly(vinylidene fluoride)/graphene oxide composites

The αc relaxation, which originates from the crystalline phase of Poly(vinylidene fluoride), is studied in the composite system of Poly(vinylidene fluoride) and Graphene oxide. PVDF/GO composites were prepared using solvent casting. The crystalline phases in PVDF/GO composites were identified using XRD and quantified using FTIR. The thermal properties were analyzed using DSC, and the crystallization degrees were calculated. The electric modulus formalism is employed to understand the relaxation mechanism with temperature. AC conductivity studies reveal the activation energy for conduction in these composites.

Na+ conductivity of (100−x)Na3PS4−xCa3N2 glass and glass−ceramics

AbstractThe ionic conductivity of Na3PS4 can be improved via the aliovalent substitution of P and S as well as multivalence cation substitution of Na. Although the enhanced ionic conductivities of tetragonal and cubic Na3PS4 have been theoretically and experimentally studied, the dynamics of sodium ions in these systems have been rarely reported. In this study, (100−x)Na3PS4−xCa3N2 (0 ≤ x ≤ 10) glass samples were synthesizing using high‐energy planetary ball‐milling method. These samples were subjected to heat treatment at 280°C for 1 h in an argon atmosphere to obtain glass–ceramic samples. The structures of these samples were characterized via Raman spectroscopy and X‐ray diffraction analysis. The lattice parameter and cell volume of the glass–ceramic samples strongly depended on the x value in (100−x)Na3PS4−xCa3N2 (0 ≤ x ≤ 10). Their ionic conductivities were determined via alternating current electrochemical impedance spectroscopy (EIS). 92Na3PS4−8Ca3N2 glass–ceramics exhibited an ionic conductivity of 8.14 × 10−4 Scm−1 at 25°C. Charge carrier concentration and hopping rate were extracted from the EIS data to determine the ionic conductivities of the samples. The activation energies of DC conductivity and mobile ion formation and migration were also derived from the EIS data to analyze the effect of Ca3N2 doping on the ionic conductivity of the synthesized samples.

Deciphering the piezoelectric and conductive mechanisms of Nb-doped Bi3Ti1.5W0.5O9 high-temperature piezoelectric ceramics

The study utilizes Bi3Ti(1.5-x)NbxW0.5O9 (BTW-xNb, x=0.00, 0.01, 0.02, 0.04, 0.06) bismuth layered piezoelectric ceramics synthesized via a conventional solid-phase reaction process. This is the study to investigate the impact of B-site Nb ion doping on the structural and electrical properties of BTW-xNb ceramic. The results show that all ceramics have a single bismuth layer structure, with reduced lattice distortion according to Rietveld refinement findings. The presence of oxygen vacancies in the ceramic is the main factor that affects the high temperature conductivity of the samples. The XPS results, the increase in the activation energy of AC and DC conductivity confirm that doping with Nb5+ ions reduces oxygen vacancy concentration. The ceramics with the highest overall electrical performance are the BTW-0.02 Nb ceramics. Notably, the DC resistivity at 500 °C was enhanced from 9.16 × 105 Ω·cm (x = 0.00) to 8.24 × 106 Ω·cm. The TC was enhanced from 730 °C(undoped) to 743 °C. At 500 °C, tanδ decreases from 21.1 % to 8.2 %. The ceramic's increased resistivity increases the polarization voltage, resulting in more complete polarization. The d33 is increased from 7.5 pC/N (undoped) to 13 pC/N. Furthermore, the piezoelectric properties remain stable up to 700°C, suggesting that the material has considerable potential for use at elevated temperatures.

Multi-scale structural regulation of negative temperature coefficient effect and electrical conduction mechanism of xSm2O3-(1-x) CaCu3Ti4O12 ceramics

In this work, a series of xSm2O3-(1-x) CaCu3Ti4O12 (xSm2O3-(1-x)CCTO, x = 0.00-0.05) negative temperature coefficient (NTC) ceramics were prepared by a solid-state method. The influence of Sm2O3 content on electrical properties was examined using microstructural, band gap, morphological, Direct Current (DC) resistivity, and impedance spectroscopy analysis. The increase in Sm2O3 content resulted in a gradual decrease of the resistivities (ρ25), thermal constants (B25/75), activation energies for electrical conduction (Ea) and activation energies of the relaxation process (Erelax) from 1.16×107 Ω•cm, 6387 K, 0.5456 eV and 0.5592 eV to 3.43×105 Ω•cm, 4149 K, 0.4088 eV and 0.4115 eV respectively. First-principles calculations revealed a reduction in the band gap by adding Sm2O3, partially explaining the decrease in electrical resistivity. In-situ XPS analysis elucidated a relationship between conduction mechanism of Sm2O3-doped CCTO ceramics and electron hopping. Impedance analyses showed that both grains and grain boundaries contributed to the NTC effect of ceramics. The electrical inhomogeneity arose from grains and grain boundaries, while local relaxation was due to the short-range motion of charge carriers.

Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified.

An inverse ferroelastic type phase transition and electric properties in bis(ethylenediammonium)tetrachlorozincate chloride crystal

Here we present TGA, DSC, dielectric studies and polarized microscopy observations of bis-ethylenediammonium tetrachlorozinc dichloride. In our studies, we found a high-temperature first-order phase transition at about 478/470 K for the heating/cooling cycle, respectively. The reversibility of the phase transition was detected by DSC and dielectric measurements and also by polarized microscopy observations. The appearance of a ferroelastic-type domain structure phase above the phase transition temperature indicates a reduction in symmetry during the heating cycle. The domain walls observed in the (100) plane are characteristic of a ferroelastic-type phase transition and can be classified as mmmF2/m Aizu species. The reduction in symmetry above the phase transition temperature allows us to classify the phase transition at 476 K as a "reverse" type. Dielectric studies in the frequency range of 40 Hz - 8 MHz allowed to estimate the activation energy for conduction and relaxation processes both with increasing and decreasing temperature. Activation energies obtained both from conductivity (σdc) measured in the temperature range from 445 to 485 K and relaxation process are practically the same both for low- and high-temperature phases as well. Taking into account the results for all directions (a, b, c) and all temperatures, conductivity is 10−7 – 10−4 S/m and is within the range characteristic for semiconductors (10−8 – 106) S/m. The conductivity and relaxation activation energies determined for the directions (a, b, c) have values in the range from 0.58 to 3.7 eV, which are also within the range characteristic for semiconductors. Electrical properties show clearly anisotropic character of the studied material.

Electrical characterization of lead-modified bismuth borovanadate glasses

Specifically, the study looks into dielectric characteristics (ε′andε″) and complex modulus formulation and AC conductivity of lead-modified bismuth borovanadate glasses (50-x) V2O5-40 B2O3-10 Bi2O3-xPbO, where x = 5,10, 15, 20 and 25 mol% with sample ID's VPb1, VPb2, VPb3, VPb4 & VPb5 according to different compositions of lead and vanadate. When the PbO content rises, there is a decreasing tendency in both the alternating current conductivity and dielectric constants. In order to fit AC conductivity data, Almond West equation is used to extract parameters, including crossover frequency (ωH), frequency exponent (s), and direct current conductivity (σdc). Direct current conduction mechanism in all glass samples except VPb5 [Correlated Barriers Hopping (CBH) conduction at all frequencies] at lower frequencies might potentially be attributed to large-polaron quantum mechanical tunneling (LQMT). Similar to this, at high frequencies, small polaron quantum mechanical tunnelling is followed by VPb2 & VPb3 while LQMT is followed by VPb1 & VPb4. Activation energy of dc conduction (Edc) at higher frequencies (0.373–0.476 eV) for samples having sample ID VPb1 to VPb4 and sample VPb5 at all frequencies with Edc 0.686 eV and modulus activation energy (ER) (0.382–0.534 eV) are found in good agreement. Dielectric studies reveal non-Debye-type behaviour.

Experimental study on Na+ conductivity in NaAlBr4 and atomic-scale investigation of Na+ conduction

AbstractThe ionic conduction properties of Li/Na metal halides have been extensively studied, with recent attention turning towards Al-based systems. However, limited studies have focused on alkali Al bromides. In this study, we explored the Na+ conduction properties of NaAlBr4. Conductivity measurements at 30 °C revealed a Na+ conductivity of 1.2 × 10−5 S/cm, surpassing that of isostructural NaAlCl4 threefold. Molecular dynamics (MD) simulations to elucidate the conduction mechanisms revealed that Na+ conduction was not observed in stoichiometric NaAlBr4, which has high formation energies of Na+ vacancies and interstitials (0.88 eV and 0.73 eV, respectively). Nevertheless, a conductivity of 1.2 × 10−5 S/cm was observed. The activation energy for ion conduction was experimentally determined as 0.43 eV, and the migration energies were calculated as 0.26 eV (Na+ vacancies) and 0.16 eV (Na+ interstitials) by MD simulations. These discrepancies in ion conduction were partially explained by the role of transient defects enriched via ball milling in facilitating Na+ conduction on the particle surface, offering insights into the complex ion conduction of ball-milled NaAlBr4.

Novel proton-conducting hexagonal perovskites Ba7In6–xYxAl2O19 for solid oxide fuel cells

The solid solution Ba7In6–xYxAl2O19 (0≤x≤0.25) with a hexagonal perovskite-like structure was prepared by the solid-state route. The introduction of yttrium was accompanied by an increase in lattice parameters. The total conductivity as a function of pO2 and T was measured at different humidity. The partial conductivities were found by transport number measurements and were fitted based on the defect formation model. Oxygen-ion and proton conductivities were found to increase with Y3+ content as a result of an increase in cell volume and free volume, which was accompanied by a decrease in the activation energy of both oxygen-ion and proton conductivity. Oxygen-ion conductivity and proton conductivity dominated below 500 °C in dry (pH2O=3.5×10−5 atm) and in wet (pH2O=1.92×10−2 atm) conditions, respectively. Doping makes it possible to increase proton conductivity by an order of magnitude (500 °C) and significantly increase the proton transport numbers.The prepared phases exhibited excellent chemical stability during thermal treatment in carbon dioxide (pCO2=1 atm).

Giant energy density with ultrahigh efficiency achieved in NaNbO3-based lead-free ceramics with polymorphic antiferrodistortive polar nanodomains

The development of dielectric ceramics with simultaneously high energy-storage density (Wrec) and efficiency (η) for capacitive energy storage poses a significant challenge. Herein, an effective strategy to achieve ultrahigh comprehensive energy-storage performance via designing polymorphic antiferrodistortive polar nanodomains is proposed, successfully realizing a giant Wrec of ∼7.5 J/cm3 with an ultrahigh η of ∼94 % in (0.9-x)NaNbO3-0.1BaZrO3-xBi(Mg0.5Ti0.5)O3 ((0.9-x)NN-0.1BZ-xBMT) lead-free ceramics at x = 0.08. The studied ceramic also exhibits excellent temperature-insensitive charge–discharge performances of high power density ∼204 ± 3 % MW/cm3, high discharge energy density ∼3.7 ± 3 % J/cm3 and fast discharge rate < 60 ns within 25–150 °C. The observation of ex-/in-situ piezoresponse force microscopy and transmission electron microscope reveals that polar nanodomains with multiple antiferrodistortive FE symmetries and diverse scales exhibit dissimilatory transformation behavior into FE microdomains during electric field loading/unloading, being responsible for a low-hysteresis polarization-field response with a near-zero remnant polarization and a high maximum polarization. Meanwhile, optimized bandgap structure and grain morphology contribute to the enhanced ceramic resistivity and conductivity activation energy as well as suppressed leakage current, resulting in significantly improved dielectric breakdown strength. These results demonstrate a feasible strategy for developing novel high-performance dielectric ceramics for high-efficiency capacitive energy storage.

Enhanced sinterability and conductivity insights of Nb2O5 - Doped 8 mol% yttria-stabilized zirconia: Implications for low-temperature ceramic electrolytes

The study explored the effect of incorporating niobia (Nb2O5) at 1, 3, and 5 wt percent into 8 mol% yttria-stabilized zirconia (8YSZ), made through a mechanochemical process. Niobia-doped 8YSZ samples were synthesized by a mechanochemical process and analyzed with methods including XRD, XPS, UV–Visible spectroscopy, particle size analysis, BET surface area analysis, FESEM-EDX, and EIS. Sintering was achieved at a reduced temperature of 1373 K, and all niobia-doped samples predominantly exhibited a tetragonal phase. Electrochemical impedance spectroscopy indicated that niobia doping inversely affected oxide ion conductivity-higher dopant concentrations resulted in lower conductivity. Nb-doped 8YSZ also displayed lower activation energy for conductivity compared to high-temperature (1473 K) sintered undoped 8YSZ, demonstrating equivalent performance. The combined benefits of lower sintering temperatures and enhanced ionic conductivities highlight crucial progress in developing cost-effective and energy-efficient electrolytes for clean energy applications.

AC Electric Conductivity of High Pressure and High Temperature Formed NaFePO4 Glassy Nanocomposite.

Olivine-like NaFePO4 glasses and nanocomposites are promising materials for cathodes in sodium batteries. Our previous studies focused on the preparation of NaFePO4 glass, transforming it into a nanocomposite using high-pressure-high-temperature treatment, and comparing both materials' structural, thermal, and DC electric conductivity. This work focuses on specific features of AC electric conductivity, containing messages on the dynamics of translational processes. Conductivity spectra measured at various temperatures are scaled by apparent DC conductivity and plotted against frequency scaled by DC conductivity and temperature in a so-called master curve representation. Both glass and nanocomposite conductivity spectra are used to test the (effective) exponent using Jonscher's scaling law. In both materials, the values of exponent range from 0.3 to 0.9, with different relation to temperature. It corresponds to the electronic conduction mechanism change from low-temperature Mott's variable range hopping (between Fe2+/Fe3+ centers) to phonon-assisted hopping, which was suggested by previous DC measurements. Following the pressure treatment, AC conductivity activation energies were reduced from EAC≈0.40 eV for glass to EAC≈0.18 eV for nanocomposite and are lower than their DC counterpart, following a typical empirical relation with the value of the exponent. While pressure treatment leads to a 2-3-orders-of-magnitude rise in the AC and apparent DC conductivity due to the reduced distance between the hopping centers, a nonmonotonic relation of AC power exponent and temperature is observed. It occurs due to the disturbance of polaron interactions with Na+ mobile ions.