Jump relaxation in solid electrolytes

Insight into ion dynamics in a NaClO4-doped polycaprolactone solid polymer electrolyte for solid state batteries

Employing low Tg polymers has fundamental limitations in providing the desirable ionic conductivity at ambient temperature due to the freezing of chain dynamics. The stiffening of polymer chains and the formation of highly ordered systems due to the crosslinks have influenced the ionic conductivity. Ionic conductivity of 1.02 × 10-5 S cm-1 was attained for the system that presented a quantum mechanical tunnelling mode of ion transport. A Na-ion transference number of 0.31 was achieved for 30 wt% of NaClO4 salt in a polycaprolactone (PCL) matrix with an electrochemical stability window of 3.6 V at 25 °C. High crystallinity and limited availability of free Na+ ions in the electrolyte have resulted in lower ionic conductivity. PCL-NaClO4 exhibited brilliant thermal stability and mechanical properties. The influence of cathode materials MnO2, V2O5 and I2 on the discharge characteristics of an electrochemical cell in the configuration cathode |(70 wt%)PCL-NaClO4(30 wt%)|Na has been studied.

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.

Reassessment of Electrical and Dielectric Properties in the Borophosphate Glass System: A Promising Solid Electrolyte for High-Temperature Batteries

This study investigates the conduction mechanism of ternary sodium borophosphate glass 30Na2O-(70 - x)B2O3-xP2O5 with 0 ≤ x ≤ 35 mol % from a different perspective, focusing on previously unreported high-temperature electrical and dielectric properties for potential solid electrolytes in high-temperature batteries. The glass composition with B2O3/P2O5 = 1 exhibits a conductivity of approximately 10-4 S/cm at 250 °C. Dielectric analysis supports this improved conduction, showing higher dielectric values and minimal energy dissipation during storage, indicating promising conductivity and favorable dielectric properties. This enhancement is attributed to the large-polaron (QMT) model, deduced from the power law exponent, due to the creation and spreading of lattice distortion of a long-range order with interconnected B4-O-P1 and B4-O-P2 linkages. Contrary to previous results, the glass transition temperature does not vary coherently with the conductivity and activation energy, displaying a discontinuity at 14 mol %. This discontinuity is caused by the initial extreme depolymerization of P2O5, leading to an increase in nonbridging oxygens (NBOs) within the glass network and forming B4-O-P0 linkages. Despite this, the ionic mobility of Na+ is continuously enhanced, correlated with the increase in the molar volume. This new perspective highlights the significant impact of both free volume expansion and reduced Coulombic effects on conduction improvement.

Structural, morphological, magnetic and electrical properties of La0.8Na0.2-x □ x MnO3 (0.00 ≤ x ≤ 0.15) manganites

La0.8Na0.2-x □ x MnO3 (0.00 ≤ x ≤ 0.15) manganites were successfully synthesized using the solid-state route. X-ray diffraction was performed to check the samples' purity and phase structure. Scanning electron microscopy analysis reveals a decrease in the average grain size with an increase in the deficiency amount. Analysis of the temperature dependence of magnetization proved the presence of ferromagnetic-paramagnetic transition in all the studied samples. The magnetization derivative (d2 M/dT 2) curves demonstrated a decrease in the transition temperature with an increase in the deficiency amount. Such experimental observations can be correlated with bandwidth evolution, which affected double-exchange interactions. It can be equally accounted for by the average grain size decrease. In this regard, the experimental measurements of effective paramagnetic moments revealed the existence of ferromagnetic correlations within the paramagnetic phase. Notably, different electrical findings were addressed. Indeed, the frequency dependence of electrical conductivity displayed the coexistence of two frequency slopes reflecting the presence of Jonscher's double power law for all the studied samples. A significant decrease in conductivity values was observed when the deficiency amount increased. This experimental observation could be assigned to the decrease in the grain size (conductor region). Such assumption was confirmed by the evolution of the grain boundary resistance with deficiency level. Indeed, a significant mounting in the grain boundary resistance values was obtained presenting the increase of the resistive region for x = 0.15. It is worth noting that the Curie temperature for the x = 0.10 sample was found to be close to room temperature (T C = 297 K). These findings make the La0.8Na0.1□0.1MnO3 compound a powerful candidate for many technological applications.

Crystal Structural Characteristics and Electrical Properties of Novel Sol-Gel Synthesis of Ceramic Bi0.75Ba0.25(FeMn)0.5O3

In this investigation, our primary objective is to explore the structural, morphological, and electrical characteristics of Bi0.75Ba0.25(FeMn)0.5O3 ceramic material synthesized by the sol-gel method. The prepared sample underwent synthesis through the conventional sol-gel technique. Examination through X-ray diffraction (XRD) unveiled a well-defined rhombohedral structure within the R3´C space group. Moreover, to evaluate the purity and nano-grain morphology, we utilized energy dispersive spectroscopy (EDX) and scanning electron microscopy (SEM). Electrical assessments were carried out over a frequency span of 100 Hz to 1 MHz and temperatures ranging from 200 to 340 K. Employing the correlated barrier hopping (CBH) model, we analyzed the AC conductivity of our specimen. The activation energy, determined from both DC conductivity and impedance spectra, demonstrated close correspondence, suggesting that both conductivity and r laxation processes are influenced by similar factors. Notably, the dielectric properties hold significant importance, potentially rendering our sample suitable for electronic applications. Furthermore, we calculated thermodynamic parameters, such as enthalpy (ΔH), entropy change (ΔS), and free energy of activation (ΔF), offering deeper insights into the material's behavior and conductivity mechanisms.

Understanding the transport properties of perovskite compounds as a function of temperature, frequency and DC-bias voltage using experimental measurements and appropriate theoretical models

The present paper provides interesting measurements and methodologies to investigate the key factors controlling the electrical response of perovskite systems. The studied system was successfully prepared using a solid-state route. The chemical analysis and the X-ray diffraction results confirm the formation of the desired perovskite phase. As a result, the DC-resistivity analysis shows that the transport properties are governed by hopping mechanisms above the transition temperature. In this case, thermal agitation allows the charge-carriers to hop across the insulating barrier in the form of grain boundaries. Then, the dominance of the grain boundary contribution is proved. AC-resistivity spectra are investigated in terms of numerous power laws (UDR, SPL and NCL). Accordingly, the decrease in the resistivity values at high frequencies is explained through hopping and tunneling processes. Indeed, it is proved that the electrical transport phenomena are governed by QMT and CBH models. The coexistence of direct (C-C) and indirect (C-A-C) interactions explains the multi-behavior of the AC-resistivity. The scaling representation displays a single muster curve describing the universal dynamic response (UDR). Thus, it reveals the universality of the electrical resistivity of the system. However, the double Schottky barrier model is used to explain the grain boundary effects. A critical frequency "νc" is detected under temperature and DC-bias voltage effects. These observations disclose, in a different way, the separate contributions of the electro-active regions of the sample in the conduction phenomenon.

DC current-voltage and impedance spectroscopy characterization of nCdS/pZnTe HJ

This paper describes the electrical and dielectric behavior of the nCdS/pZnTe HJ by current-voltage, capacitance-voltage characteristics, and impedance spectroscopy in a temperature interval 220-350 K. A microcrystalline p-ZnTe layer and n-CdS were grown on glass/ZnO substrate by closed space sublimation method. As frontal contact to CdS, the transparent ZnO and as a back contact to ZnTe, silver conductive paste (Ag) treated at 50 °C in vacuum were used. The current-voltage results of nCdS/pZnTe HJ show a rectifying behavior. The junction ideality factor, barrier height, and series resistance values were extracted from the rectifying curves at different temperatures. The built-in voltage, carrier concentration and depletion width were obtained from the capacitance-voltage measurements. Analysis of the J-V-T and C-V-T characteristics shows that the thermionic emission and recombination current flow mechanisms dominate in the nCdS/pZnTe HJ. The dielectric study reveals that the experimental values of the AC conductivity, dielectric constant, dielectric loss, the imaginary part of the electric modulus are found to be very sensitive to frequency and temperature. The dielectric constant and dielectric loss are observed to be high at the low frequency region. The increase in the values of electric modulus with the frequency implies an increase in the interfacial polarization at the interface of nCdS/pZnTe HJ. Jonscher's universal power law shows that with increasing frequency, AC conductivity increased. The results conductivity show that the ionic conductivity and interfacial polarization are the main parameters affecting the dielectric properties of the device when the temperature changes.

Investigating Fe-doped Ba0.67Ni0.33Mn1-xFexO3 (x = 0, 0.2) ceramics: insights into electrical and dielectric behaviors

This study investigates the characteristics of the Ba0.67Ni0.33Mn1-xFexO3 perovskite compound, focusing on its structural and electrical aspects under varying Fe doping levels at the Mn-site (x = 0, 0.2). X-ray diffraction patterns confirm the material's consistent structure, with Fe3+ ions substituting Mn3+ ions while maintaining their identical ionic radius. Nano-crystallinity studies reveal single-phase crystallization in the orthorhombic structure with space group Imma. Samples are prepared through conventional solid-state sintering. The Williamson-Hall method calculates crystallite sizes, averaging 37 nm for x = 0 and 33 nm for x = 0.2. Electrical properties are examined using complex impedance spectroscopy at different temperatures and frequencies. Techniques such as energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) assess chemical composition. Activation energy values increase from 0.138 eV for x = 0 to 0.171 eV for x = 0.2, leading to reduced dc conductivity across the investigated temperature range. Dielectric permittivity enhances proportionally with increasing Fe doping. Variations in impedance profiles reveal a relaxation phenomenon. A circuit model, Rg + (Rgb//CPEgb), elucidates impedance data. This study illuminates the interplay between Fe doping, activation energy, and electrical conductivity in Ba0.67Ni0.33Mn1-xFexO3 perovskite, offering insights applicable to electronic and energy-related devices. Perovskite-based nanomaterials have diverse environmental applications, including solar cells, light-emitting devices, transistors, sensors, and energy storage.

Ionic Conductivity of a Lithium-Doped Deep Eutectic Solvent: Glass Formation and Rotation-Translation Coupling

Deep eutectic solvents with admixed lithium salts are considered as electrolytes in electrochemical devices, such as batteries or supercapacitors. Compared to eutectic mixtures of hydrogen-bond donors and lithium salts, their raw-material costs are significantly lower. Not much is known about glassy freezing and rotational-translation coupling of such systems. Here, we investigate these phenomena by applying dielectric spectroscopy to the widely studied deep eutectic solvent glyceline, to which 1 and 5 mol % LiCl were added. Our study covers a wide temperature range, including a deeply supercooled state. The temperature dependences of the detected dipolar reorientation dynamics and ionic direct current (dc) conductivity reveal the signatures of glassy freezing. In comparison to pure glyceline, the lithium admixture leads to a reduction of ionic conductivity, which is accompanied by a reduction of the rotational dipolar mobility. However, this reduction is much smaller than that for deep eutectic solvents (DESs), where one main component is lithium salt, which we trace back to the lower glass-transition temperatures of lithium-doped DESs. In contrast to pure glyceline, the ionic and dipolar dynamics become increasingly decoupled at low temperatures and obey a fractional Debye-Stokes-Einstein relation, as previously found in other glass-forming liquids. The obtained results demonstrate the relevance of decoupling effects and glass transition to the enhancement of the technically relevant ionic conductivity in such lithium-doped DESs.

Structural, morphological, electrical, and dielectric properties of Na2Cu5(Si2O7)2 for ASSIBs

Solid inorganic electrolyte materials are fundamental components for constructing all-solid-state sodium-ion batteries. These solid electrolytes offer considerable benefits related to safety, electrochemical performance, and mechanical stability in comparison to liquid organic electrolyte systems. This study investigates the sodium ion conduction mechanism and relaxation kinetics in the sorosilicate material Na2Cu5(Si2O7)2, a potential solid electrolyte, using impedance spectroscopy. Analysis of the DC conductivity data demonstrates that sodium ion mobility follows Arrhenius behavior with a thermal activation energy barrier of 1.21 eV. This work highlights the importance of carefully choosing an appropriate equivalent circuit model to extract DC conductivity parameters from impedance data, given the contributions from both grain and grain boundary effects. Analysis of the AC conductivity and dielectric constant as a function of frequency and temperature demonstrates that ionic conduction takes place in this material through a process in which charge carriers overcome correlated energy barriers, known as correlated barrier hopping. The neutron diffraction patterns were analyzed using soft bond valence sum (BVS) techniques to map the possible ionic conduction pathways within the unit cell. Examination of the data points to obstructions in the sodium ion diffusion routes along the a-axis and diagonal of the bc plane within the triclinic unit cell. These bottlenecks likely contribute to the high activation energy and correspondingly low ionic conductivity observed. Analysis of dielectric properties by modulus verified that the ionic conduction relaxation phenomena exhibit thermal activation and a distribution of relaxation times. In summary, this work elucidates the microscopic ionic conduction mechanism in Na2Cu5(Si2O7)2 through extensive analysis encompassing DC/AC conductivity, electric modulus, and dielectric constant measurements. The insights gained into the ionic conduction mechanism will aid in engineering optimized ionic conductor materials for battery technologies.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Hysteresis and Its Correlation to Ionic Defects in Perovskite Solar Cells

Ion migration has been reported to be one of the main reasons for hysteresis in the current-voltage (J-V) characteristics of perovskite solar cells. We investigate the interplay between ionic conduction and hysteresis types by studying Cs0.05(FA0.83MA0.17)0.95Pb(I0.9Br0.1)3 triple-cation perovskite solar cells through a combination of impedance spectroscopy (IS) and sweep-rate-dependent J-V curves. By comparing polycrystalline devices to single-crystal MAPbI3 devices, we separate two defects, β and γ, both originating from long-range ionic conduction in the bulk. Defect β is associated with a dielectric relaxation, while the migration of γ is influenced by the perovskite/hole transport layer interface. These conduction types are the causes of different types of hysteresis in J-V curves. The accumulation of ionic defects at the transport layer is the dominant cause for observing tunnel-diode-like characteristics in the J-V curves. By comparing devices with interface modifications at the electron and hole transport layers, we discuss the species and polarity of involved defects.

Rotational dynamics, ionic conductivity, and glass formation in a ZnCl2-based deep eutectic solvent

Glass formation and reorientational motions are widespread but often-neglected features of deep eutectic solvents although both can be relevant for the technically important ionic conductivity at room temperature. Here, we investigate these properties for two mixtures of ethylene glycol and ZnCl2, which were recently considered superior electrolyte materials for application in zinc-ion batteries. For this purpose, we employed dielectric spectroscopy performed in a broad temperature range, extending from the supercooled state at low temperatures up to the liquid phase around room temperature and beyond. We find evidence for a relaxation process arising from dipolar reorientation dynamics, which reveals the clear signatures of glassy freezing. This freezing also governs the temperature dependence of the ionic dc conductivity. We compare the obtained results with those for deep eutectic solvents that are formed by the same hydrogen-bond donor, ethylene glycol, but by two different salts, choline chloride and lithium triflate. The four materials reveal significantly different ionic and reorientational dynamics. Moreover, we find varying degrees of decoupling of rotational dipolar and translational ionic motions, which can partly be described by a fractional Debye-Stokes-Einstein relation. The typical glass-forming properties of these solvents strongly affect their room-temperature conductivity.

The Effect of Doping on the Electrical and Dielectric Properties of Hydroxyapatite for Medical Applications: From Powders to Thin Films

Recently, the favorable electrical properties of biomaterials have been acknowledged as crucial for various medical applications, including both bone healing and growth processes. This review will specifically concentrate on calcium phosphate (CaP)-based bioceramics, with a notable emphasis on hydroxyapatite (HA), among the diverse range of synthetic biomaterials. HA is currently the subject of extensive research in the medical field, particularly in dentistry and orthopedics. The existing literature encompasses numerous studies exploring the physical-chemical, mechanical, and biological properties of HA-based materials produced in various forms (i.e., powders, pellets, and/or thin films) using various physical and chemical vapor deposition techniques. In comparison, there is a relative scarcity of research on the electrical and dielectric properties of HA, which have been demonstrated to be essential for understanding dipole polarization and surface charge. It is noteworthy that these electrical and dielectric properties also offer valuable insights into the structure and functioning of biological tissues and cells. In this respect, electrical impedance studies on living tissues have been performed to assess the condition of cell membranes and estimate cell shape and size. The need to fill the gap and correlate the physical-chemical, mechanical, and biological characteristics with the electrical and dielectric properties could represent a step forward in providing new avenues for the development of the next-generation of high-performance HA-doped biomaterials for future top medical applications. Therefore, this review focuses on the electrical and dielectric properties of HA-based biomaterials, covering a range from powders and pellets to thin films, with a particular emphasis on the impact of the various dopants used. Therefore, it will be revealed that each dopant possesses unique properties capable of enhancing the overall characteristics of the produced structures. Considering that the electrical and dielectric properties of HA-based biomaterials have not been extensively explored thus far, the aim of this review is to compile and thoroughly discuss the latest research findings in the field, with special attention given to biomedical applications.

Influence of the Addition of Zinc, Strontium, or Magnesium Oxides to the Bioglass 45S5 Network on Electrical Behavior

45S5 Bioglass has been widely used in regenerative medicine due to its ability to dissolve when inserted into the body. Its typically amorphous structure allows for an ideal dissolution rate for the formation of the hydroxyapatite layer, which is important for the development of new bone. This bioactive capacity can also be controlled by adding other oxides (e.g., SrO, ZnO, and MgO) to the 45S5 Bioglass network or by storing electrical charge. Ions such as zinc, magnesium, and strontium allow for specific biological responses to be added, such as antibacterial action and the ability to increase the rate of osteoblast proliferation. The charge storage capacity allows for a higher rate of bioactivity to be achieved, allowing for faster attachment to the host bone, decreasing the patient's recovery time. Therefore, it is necessary to understand the variation in the structure of the bioglass with regard to the amount of non-bridging oxygens (NBOs), which is important for the bioactivity rate not to be compromised, and also its influence on the electrical behavior relevant to its potential as electrical charge storage. Thus, several bioactive glass compositions were synthesized based on the 45S5 Bioglass formulation with the addition of various concentrations (0.25, 0.5, 1, and 2, mol%) of zinc, strontium, or magnesium oxides. The influence of the insertion of these oxides on the network was evaluated by studying the amount of NBOs using Raman spectroscopy and their implication on the electrical behavior. Electrical characterization was performed in ac (alternating current) and dc (direct current) regimes.

High-Entropy Lead-Free Perovskite Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 Powders and Related Ceramics: Synthesis, Processing, and Electrical Properties

A novel high-entropy perovskite powder with the composition Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 was successfully synthesized using a modified Pechini method. The precursor powder underwent characterization through Fourier Transform Infrared Spectroscopy and thermal analysis. The resultant Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 powder, obtained post-calcination at 900 °C, was further examined using a variety of techniques including X-ray diffraction, Raman spectroscopy, X-ray fluorescence, scanning electron microscopy, and transmission electron microscopy. Ceramic samples were fabricated by conventional sintering at various temperatures (900, 950, and 1000 °C). The structure, microstructure, and dielectric properties of these ceramics were subsequently analyzed and discussed. The ceramics exhibited a two-phase composition comprising cubic and tetragonal perovskites. The grain size was observed to increase from 35 to 50 nm, contingent on the sintering temperature. All ceramic samples demonstrated relaxor behavior with a dielectric maximum that became more flattened and shifted towards lower temperatures as the grain size decreased.

Study of the effect of the substitution of Fe by Ti on the microstructure and the physical properties of the perovskite system La0.67Ca0.2Ba0.13Fe1-xTixO3 with x = 0 and 0.03 at low temperatures

La0.67Ca0.2Ba0.13Fe1-xTixO3 samples (x = 0 and 0.03) were synthesized by the auto-combustion method. Analysis of XRD diffractograms revealed that these compounds crystallize in the cubic system with the space group Pm3̄m. The dielectric properties have been studied in the 102-106 frequency range and the 120-280 K temperature range. Analysis of AC conductivity shows that the conduction mechanisms are of polaronic origin and that they are co-dominated by the NSPT and OLPT models. The monotonic increase in conductivity with increasing temperature results from the reduction of defect centers and the increase in charge carrier mobility. Such variation is consistent with impedance variation at different frequencies and temperatures indicating semiconductor behavior. Nyquist diagrams are characterized by the appearance of semi-circular arcs. These spectra are modeled in terms of equivalent electrical circuits confirming the contribution of grains (Rg//CPEg) and grain boundaries (Rgb//CPEgb). The dielectric analysis showed an evolution of the dielectric constant in accordance with Koop's theory and the phenomenological model of Maxwell-Wagner. The low conductivity and the high values of the real permittivity at low frequency make our compounds potential candidates for energy storage and applications for electronic devices and microwaves.

Electronic, electrical and thermoelectric properties of Ba0.95Ca0.05Ti0.95Y0.05O2.975 compound: Experimental study and DFT-mBJ calculation

This article explores the impact of co-doping BaTiO3 ceramics with Ca2+ and Y3+ using solid-state reactions to improve its dielectric constant and decrease losses. The oxide BCTYO (Ba0.95Ca0.05Ti0.95Y0.05O2.975) exhibits a tetragonal crystal structure, characterized by a space group of P4mm. By examining the behavior of the doped BaTiO3 sample and performing simulations, researchers can better understand the underlying mechanisms and optimize material properties for specific applications. DFT study shows a semiconductor behavior with an indirect gap (Eg = 2.5 eV). The partial DOS proves that the hybridization between the orbitals Ti 3d, Y 3d, and O 2p is responsible for the band gap and the hopping processes. The analysis of conductivity curves provides evidence for the semiconductor characteristics of the material under investigation. By determining the activation energy (Ea) through analyzing Ln(fmax) and conductivity as a function of 1000/T, the interconnection between conduction and relaxation phenomena is demonstrated. The study of the real part of the dielectric permittivity (ε') shows a transition at Tc = 380 K. The obtained results are promising and indicate that the studied material has the potential for various electronic applications (energy storage and diode fabrication …). Moreover, the thermal, electrical, and thermoelectric characteristics were examined utilizing the semi-classical Boltzmann theory. The findings revealed an intriguing result, suggesting that Ba0.95Ca0.05Ti0.95Y0.05O2.975 holds promise as a potential candidate for application in thermoelectric devices.

Ion Hopping: Design Principles for Strategies to Improve Ionic Conductivity for Inorganic Solid Electrolytes

Solid electrolytes are considered as an ideal substitution of liquid electrolytes, avoiding the potential hazards of volatilization, flammability, and explosion for liquid electrolyte-based rechargeable batteries. However, there are significant performance gaps to be bridged between solid electrolytes and liquid electrolytes; one with a particular importance is the ionic conductivity which is highly dependent on the material types and structures. In this review, the general physical image of ion hopping in the crystalline structure is revisited, by highlighting two main kernels that impact ion migration: ion hopping pathways and skeletons interaction. The universal strategies to effectively improve ionic conductivity of inorganic solid electrolytes are then systematically summarized: constructing rapid diffusion pathways for mobile ions; and reducing resistance of the surrounding potential field. The scoped strategies offer an exclusive view on the working principle of ion movement regardless of the ion species, thus providing a comprehensive guidance for the future exploitation of solid electrolytes.

Investigation of the structural, electrical, and dielectric properties of La0.5Sm0.2Sr0.3Mn1-x Cr x O3 for electrical application

In the present research, polycrystalline samples of La_0.5Sm_0.2Sr_0.3Mn_1−xCr_xO₃ are prepared using the self-combustion method. Then, we have studied their crystalline structure, and dielectric and electrical properties. The X-ray diffraction study shows that all the samples exhibit a single phase with orthorhombic structure (space group Pnma). The studied samples were also characterized by complex impedance spectroscopy in a wide range of temperatures and frequency. AC conductivity analyses are used to study the transport property of the investigated samples. These analyses indicate that the conduction mechanism is strongly dependent on temperature and frequency. It is also found that the conductivity decreases with Cr concentration. Complex impedance analysis confirms the contributions of grain and grain boundaries in the conduction mechanism. Finally, the impedance spectra, characterized by the appearance of semicircle arcs at different temperatures, were well modeled in terms of equivalent electrical circuits to explain the impedance results.

In the present research, polycrystalline samples of La_0.5Sm_0.2Sr_0.3Mn_1−xCr_xO₃ are prepared using the self-combustion method.

Ionic Conductivity of Nanocrystalline and Amorphous Li10GeP2S12: The Detrimental Impact of Local Disorder on Ion Transport

Solids with extraordinarily high Li⁺ dynamics are key for high performance all-solid-state batteries. The thiophosphate Li₁₀GeP₂S₁₂ (LGPS) belongs to the best Li-ion conductors with an ionic conductivity exceeding 10 mS cm^–1 at ambient temperature. Recent molecular dynamics simulations performed by Dawson and Islam predict that the ionic conductivity of LGPS can be further enhanced by a factor of 3 if local disorder is introduced. As yet, no experimental evidence exists supporting this fascinating prediction. Here, we synthesized nanocrystalline LGPS by high-energy ball-milling and probed the Li⁺ ion transport parameters. Broadband conductivity spectroscopy in combination with electric modulus measurements allowed us to precisely follow the changes in Li⁺ dynamics. Surprisingly and against the behavior of other electrolytes, bulk ionic conductivity turned out to decrease with increasing milling time, finally leading to a reduction of σ_20°C by a factor of 10. ³¹P, ⁶Li NMR, and X-ray diffraction showed that ball-milling forms a structurally heterogeneous sample with nm-sized LGPS crystallites and amorphous material. At −135 °C, electrical relaxation in the amorphous regions is by 2 to 3 orders of magnitude slower. Careful separation of the amorphous and (nano)crystalline contributions to overall ion transport revealed that in both regions, Li⁺ ion dynamics is slowed down compared to untreated LGPS. Hence, introducing defects into the LGPS bulk structure via ball-milling has a negative impact on ionic transport. We postulate that such a kind of structural disorder is detrimental to fast ion transport in materials whose transport properties rely on crystallographically well-defined diffusion pathways.

Effect of Sintering Temperature and Polarization on the Dielectric and Electrical Properties of La0.9Sr0.1MnO3 Manganite in Alternating Current

The electrical characterization ofa La_0.9Sr_0.1MnO₃ compound sintered at 800, 1000 and 1200 °C was investigated by means of the impedance-spectroscopy technique. As the results, the experimental conductivity spectra were explained in terms of the power law. The AC-conductivity study reveals the contributions of different conduction mechanisms. Indeed, the variation in the frequency exponents (‘s₁’ and ‘s₂’) as a function of the temperature confirms the thermal activation of the conduction process in the system. It proves, equally, that the transport properties are governed by the non-small-polaron-tunneling and the correlated-barrier-hopping mechanisms. Moreover, the values of the frequency exponents increase under the sintering-temperature (TS) effect. Such an evolution may be explained energetically. The jump relaxation model was used to explain the electrical conductivity in the dispersive region, as well as the frequency-exponent values by ionic conductivity. Under electrical polarization with applied DC biases of Vp = 0.1 and 2 V at room temperature, the results show the significant enhancement of the electrical conductivity. In addition, the dielectric study reveals the evident presence of dielectric relaxation. Under the sintering-temperature effect, the dielectric constant increases enormously. Indeed, the temperature dependence of the dielectric constant is well fitted by the modified Curie–Weiss law. Thus, the deduced values of the parameter (γ) confirm the relaxor character and prove the diffuse phase transition of our material. Of note is the high dielectric-permittivity magnitude, which indicates that the material is promising for microelectronic devices.

Evaluation of the microstructure, optical properties and hopping conduction mechanism of rare earth doped Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 ceramics (RE = Ce3+ and Pr3+)

The current research work examines the impact of Rare Earth (RE3+) ion substitution on the structural, optical and conduction properties of a Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 (BCRETZN) (RE = Ce, Pr) ceramic compound produced via a solid-state route. The Rietveld method of the X-ray data revealed a tetragonal (P4mm) structure at room temperature for our ceramic compound. The morphology of the compound was explored using Scanning Electron Microscopy (SEM) as well as optical response and conduction behavior. The photoluminescence properties revealed that the BCPrTZN sample results in green and red photoemissions under laser excitation at 450 nm at RT. Furthermore, for the BCCeTZN sample, the photoluminescence data demonstrated that strong violet emission bands were acquired, at RT upon an excitation at 350 nm. The electrical conduction process was verified via the correlated barrier Hopping method. The scaling behavior suggests that the electrical conduction mechanism is independent of temperature. The existence of Ce3+ and Pr3+ ions in these materials could have important technological potential in new multifunctional devices.

Lithium ion transport in micro- and nanocrystalline lithium sulphide Li2S

Ion dynamics in binary Li-bearing compounds such as LiF, Li2O and Li2S is rather poor. These compounds do, however, form as decomposition products at the interface between the electrolyte and the electrode materials in lithium-based batteries. They are expected to severely influence the charge transport across this electrode-electrolyte interface and, thus, the overall performance of such systems. Yet, ion dynamics in the nanostructured forms of these binary compounds has scarcely been investigated. Here, we prepared bulk nanostructured Li2S through high-energy ball milling and studied its temperature-dependent ionic conductivity by means of broadband impedance spectroscopy. It turned out that, compared to the unmilled form, Li+ ion conductivity in ball-milled Li2S increased by approximately 3 orders or magnitude. This striking increase is accompanied by a decrease of the average activation energy from ca. 0.9 eV to approximately 0.7 eV. Structural disorder, stress and local distortions are assumed to be responsible for this clear change in macroscopic transport parameters. Fast ion dynamics in or near the interfacial space charge zones might contribute to enhanced dynamics, too. We conclude that Li ion transport in interfacial Li2S, if present in a disordered nanostructured form in lithium-ion batteries, is much faster than originally thought for its ordered counterpart.

Electric and Dielectric Properties in Low-Frequency Fields of Composites Consisting of Silicone Rubber and Al Particles for Flexible Electronic Devices

Understanding the electrical conduction and dielectric polarization properties of elastomer-based composites is important for the design of flexible and elastic electronic devices and circuits. Five samples were manufactured by mixing silicone rubber (RTV-530) with Al particles in different volume fractions, x equal to 0%, 0.5%, 1%, 2.5% and 5.1%. Using the complex impedance measurements, the electric modulus, M, the electrical conductivity, σ, and the dielectric permittivity, ε, over the frequency range 100 Hz–200 kHz were analyzed. The electrical conductivity spectrum, σ(f), follows the Jonscher universal law and the DC conductivity of the samples, σ_DC, increases from 2.637·10⁻⁸ S/m to 5.725·10⁻⁸ S/m, with increasing x from, 0 to 5.1%. The conduction process was analyzed in terms of Mott’s variable-range-hopping (VRH) model. The hopping distance of the charge carriers, R_h decreases with increasing x, from 7.30 nm (for x = 0) to 5.92 nm (for x = 5.1%). The frequency dependence of permittivity, ε(f) = ε′(f) − iε″(f), reveals a relaxation process with the maximum of ε″(f) shifting from 301 Hz to 385 Hz and values of ε′(f) increasing with the increase of x.

Investigation of optical and electrical properties of the semiconducting α-KZnPO4 compound

We used the solid state method to synthesize the α-KZnPO4 compound. The X-ray diffraction pattern revealed that the sample represents a single hexagonal phase with a P63 space group. The chemical composition of the compound was examined by energy dispersive spectroscopy. The optical absorption measurement confirmed the semiconductor nature of the compound with a band gap around 4.52 eV. Furthermore, the electrical properties of the material were analyzed by means of the impedance spectroscopy, in a frequency range from 100 Hz to 1 MHz and a temperature range from 583 K to 673 K. The dependency of s(T) on temperature showed that the overlapping large polaron tunneling model is the mechanism responsible for AC conduction in the compound. A correlation between the crystal structure and the ionic conductivity was established and discussed. Finally, the temperature variation of M'' peak showed a thermally activated relaxation process and a temperature-dependent stretching exponent β parameter.

Opening Diffusion Pathways through Site Disorder: The Interplay of Local Structure and Ion Dynamics in the Solid Electrolyte Li6+xP1–xGexS5I as Probed by Neutron Diffraction and NMR

Solid electrolytes are at the heart of future energy storage systems. Li-bearing argyrodites are frontrunners in terms of Li⁺ ion conductivity. Although many studies have investigated the effect of elemental substitution on ionic conductivity, we still do not fully understand the various origins leading to improved ion dynamics. Here, Li_6+xP_1–xGe_xS₅I served as an application-oriented model system to study the effect of cation substitution (P⁵⁺ vs Ge⁴⁺) on Li⁺ ion dynamics. While Li₆PS₅I is a rather poor ionic conductor (10^–6 S cm^–1, 298 K), the Ge-containing samples show specific conductivities on the order of 10^–2 S cm^–1 (330 K). Replacing P⁵⁺ with Ge⁴⁺ not only causes S^2–/I^– anion site disorder but also reveals via neutron diffraction that the Li⁺ ions do occupy several originally empty sites between the Li rich cages in the argyrodite framework. Here, we used ⁷Li and ³¹P NMR to show that this Li⁺ site disorder has a tremendous effect on both local ion dynamics and long-range Li⁺ transport. For the Ge-rich samples, NMR revealed several new Li⁺ exchange processes, which are to be characterized by rather low activation barriers (0.1–0.3 eV). Consequently, in samples with high Ge-contents, the Li⁺ ions have access to an interconnected network of pathways allowing for rapid exchange processes between the Li cages. By (i) relating the changes of the crystal structure and (ii) measuring the dynamic features as a function of length scale, we were able to rationalize the microscopic origins of fast, long-range ion transport in this class of electrolytes.

Novel Dispersion of 1D Nanofiber Fillers for Fast Ion-Conducting Nanocomposite Polymer Blend Quasi-Solid Electrolytes for Dye-Sensitized Solar Cells

Electrospun nanocomposite polymer blend poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(methyl methacrylate) (PMMA) membranes with a novel dispersion of x wt % of one-dimensional (1D) TiO₂ nanofiber fillers (x = 0.0-0.8 in steps of 0.2) were developed using the electrospinning technique. The developed nanocomposite polymer membranes were activated using various redox agents such as LiI, NaI, KI, and tetrabutyl ammonium iodide (TBAI). Introduction of the 1D TiO₂ nanofiber fillers improves the amorphous nature of the blended polymer membrane, as confirmed through X-ray diffraction (XRD) and Fourier transform infrared (FTIR), and yielded an electrolyte uptake of over 480% for a 6 wt % TiO₂ nanofiber filler-dispersed sample. PVDF-HFP/PMMA-1D 6 wt % TiO₂ nanofiber fillers with the LiI-based redox electrolyte provided a high conductivity of 2.80 × 10^-2 S cm^-1 and a power conversion efficiency (PCE) of 8.08% to their fabricated dye-sensitized solar cells (DSSCs). The observed better ionic conductivity and efficiency of the fabricated DSSCs could be due to the faster movement of the smaller-ionic-radius (Li) ions entrapped inside the amorphous polymer. This enhanced mobility of ions in the quasi-solid electrolyte leads to faster regeneration of the depleting electrons in the photoanode, resulting in improved efficiency. Further, the achieved high conductivity was analyzed in terms of the dynamics and relaxation mechanisms involved by the ionic charge carriers with complex impedance spectroscopy using a random barrier model and Havriliak-Negami formulation. It was observed that the high-conducting PVDF-HFP/PMMA-1D 6 wt % TiO₂ nanofiber fillers with LiI-based redox electrolyte show better ac conductivity parameters such as a σ of 5.82 × 10^-2 S cm^-1, ω_e (12685 rad s^-1), τ_e (0.909 × 10^-4 s), and n (0.578). Also, dielectric studies revealed that the high-conducting sample has a higher dielectric constant and subsequently high loss. The J-V characteristics were studied using the equivalent circuit of a single-diode model, and the parameters influencing the photovoltaic performance were determined by Symbiotic Organisms Search (SOS) algorithm. The results suggest that the high-efficient sample possesses a minimum series resistance of 1.33 Ω and a maximum shunt resistance of 997 Ω. Hence, the highest-conducting electrospun-blended polymeric nanocomposite (PVDF-HFP-PMMA-6 wt % TiO₂ nanofiber fillers) with LiI-based redox agent and tert-butyl pyridine (TBP) additive as the polymer quasi-solid electrolyte nanofibrous membrane can be a better electrolyte for high-performance dye-sensitized solar cell applications.

Structural, optical and conductivity properties in tetragonal BaTi1−xCoxO3 (0≤ x ≤0.1)

This work investigates the structure, optical and electrical conductivity properties of BaTi_1−xCo_xO₃ (0≤ x ≤0.1) ceramics prepared by the hydrothermal method. The X-ray diffraction and Raman scattering analysis demonstrates that the prepared samples have a single-phase tetragonal structure with P4mm symmetry. The UV-vis diffuse reflectance spectrum confirms the influence of Co concentration on the direct optical band gap of BaTi_1−xCo_xO₃ ceramics. The optical band gap shifts from 3.14 eV to 3.44 eV as the Co concentration increases from 0 to 0.1. The dielectric constant increases with the depletion of frequency according to the Maxwell–Wagner and Koops model. The AC conductivity versus frequency curve indicates that the conduction mechanism is determined by using the correlated barrier hopping (CBH) model. The Cole–Cole plot of the complex impedance was investigated for the prepared samples. The compounds showed dielectric relaxation of the non-Debye type.

This work investigates the structure, optical and electrical conductivity properties of BaTi_1−xCo_xO₃ (0≤ x ≤0.1) ceramics prepared by the hydrothermal method.

Low-frequency dynamics in ionic liquids: Comparison of experiments and the random barrier model

By examining the fine features of dielectric spectra of ionic liquids, we show that the derivative of real permittivity progressively broadens at low frequencies when the glass transition is approached...

Ion Transport Mechanism in Anhydrous Lithium Thiocyanate LiSCN Part II: Frequency Dependence and Slow Jump Relaxation

Specific aspects of the Li+ cation conductivity of anhydrous Li(SCN) are investigated, in particular the high migration enthalpy of lithium vacancies. Close inspection of impedance spectra and conductivity data reveals...

Cooperative excitations in superionic PbF2

Links between dynamical Frenkel defects and collective diffusion of fluorides in β-PbF₂ are explored using Born-Oppenheimer molecular dynamics. The calculated self-diffusion coefficient and ionic conductivity are 3.2 × 10^-5 cm² s^-1 and 2.4 Ω^-1 cm^-1 at 1000 K in excellent agreement with pulsed field gradient and conductivity measurements. The calculated ratio of the tracer-diffusion coefficient and the conductivity-diffusion coefficient (the Haven ratio) is slightly less than unity (about 0.85), which in previous work has been interpreted as providing evidence against collective 'multi-ion' diffusion. By contrast, our molecular dynamics simulations show that fluoride diffusion is highly collective. Analysis of different mechanisms shows a preference for direct collinear 'kick-out' chains where a fluoride enters an occupied tetrahedral hole/cavity and pushes the resident fluoride out of its cavity. Jumps into an occupied cavity leave behind a vacancy, thereby forming dynamic Frenkel defects which trigger a chain of migrating fluorides assisted by local relaxations of the lead ions to accommodate these chains. The calculated lifetime of the Frenkel defects and the collective chains is approximately 1 ps in good agreement with that found from neutron diffraction. This article is part of the Theo Murphy meeting issue 'Understanding fast-ion conduction in solid electrolytes'.

Synthesis and Characterization of Yttrium-Doped Hydroxyapatite Nanoparticles and Their Potential Antimicrobial Activity

This study reports a detailed analysis of the yttrium doping effects into hydroxyapatite (HAp) nano-structures at different amounts (e.g., 0, 1, 2.5, 5, 7.5, 10, and 15%) on the structural, spectroscopic, dielectric, and antimicrobial properties. For this purpose, seven HAp samples having the Y-contents mentioned above were prepared using the microwave-assisted sol-gel precipitation technique. The structure of synthesized samples was fully described via X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared (FTIR). Raman spectroscopy and dielectric measurements were used to characterize the spectroscopic properties. Furthermore, the samples’ antimicrobial features have been assisted through the agar disk diffusion technique. This study showed that the crystallinity decreased with the adding of Y-ions inside the HAp matrix. The Y-contents have influenced the crystallite size, lattice parameters, dislocation density, lattice strain, and unit cell volume. The surface morphology is composed of the agglomerated smaller particles. Remarkable changes in the dielectric properties were observed with the adding of Y-ions. The alternating current conductivity obeys the Jonscher’s relation. Y-doped hydroxyapatite nanoparticles have a considerable inhibitory effect against bacteria and fungi (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans). The Y-doped hydroxyapatite nanoparticles are a promising material for bone cement engineering with a potential bio-activity