High Dielectric Permittivity Research Articles

Microstructure, low loss tangent, and excellent temperature stability of Tb+Sb-doped TiO2 with high dielectric permittivity

The study of colossal permittivity (CP) materials possessing very high dielectric constants (ε′ > 104) has gained traction due to their suitability for application in microelectronic devices, which are evolving rapidly. In addition, the loss tangent (tanδ) and temperature stability of ε′ are crucial factors to consider for actual applications. In this study, (Tb3+/4++Sb5+) co-doped TiO2 (TSTO) ceramic with an appropriate co-dopant content presented an extremely high ε′ value of ∼9.31 × 104 and ultra-low tanδ (∼0.013) at 1 kHz. Moreover, its temperature-dependent coefficient of permittivity deviation (Δε'(T)/ε'30°C) was lower than |±15%| over the temperature range from −60 ℃ to 210 ℃. The TSTO ceramics exhibited highly compact microstructures. The grains, grain boundaries, and microwave dielectric phases (i.e., Tb2Ti2O7) were detected, and their presence is considered to determine the dielectric behavior of the TSTO ceramic. The observation of Ti3+ induced by Sb5+ via X-ray photoelectron spectroscopy explains the appearance of semiconducting grains, as confirmed by impedance spectroscopy (IS). The high resistivity resulting from the grain boundaries and microwave dielectric phase was also confirmed by IS. The findings describe the CP properties of TSTO ceramics via the interfacial polarization process and demonstrate that the existence of microwave dielectric phase particles with appropriate content affects the dielectric relaxation, resulting in the reduction of tanδ.

Last developments in polymers for wearable energy storage devices

Last developments in polymers for wearable energy storage devices

Giant dielectric behavior and non-ohmic properties in Mg2++F− co-doped CaCu3Ti4O12 ceramics

ABSTRACT A solid–state reaction method was used to produce CaCu3-x Mg x Ti4O12-2x F2x with x values of 0, 0.05, and 0.10. A CaCu3Ti4O12 phase was detected in the absence of impurities. The (Mg2++F–) co–doping ions inhibited the grain growth of the CaCu3Ti4O12 ceramics because of the solute drag mechanism. The dielectric and non–Ohmic electrical properties of the CaCu3-x Mg x Ti4O12-2x F2x ceramics were studied. Intriguingly, the ceramic with x = 0.05 enhanced the dielectric properties with a considerably decreased loss tangent (tanδ~0.06) while retaining a high dielectric permittivity (>104) at 1 kHz. The nonlinear current density–electric field (J–E) properties of the ceramic with x = 0.05 were also successfully improved. However, the dielectric and nonlinear properties deteriorated when x = 0.10. The variations in the low–frequency tanδ and electric breakdown strength were primarily associated with the grain size and Schottky barrier height at the grain boundaries. The relevant mechanisms for these improved dielectric and non–Ohmic properties are discussed based on the effect of the internal barrier layer capacitor.

Terahertz response of Er3+/Yb3+ co-doped La2Zr2O7 synthesized using the sol-gel precipitation method

Oxide ceramics with pyrochlore structure such as La2Zr2O7 are promising materials for advanced multifunctional applications including extreme environment, such as space applications. They combine low thermal conductivity, suitable coefficient of thermal expansion to join supporting materials and have optical response in the UV–VIS region with up-converting and down-converting properties after doping, required for coating, sensors, and electro-optic applications. The effect of doping elements such as Er3+ and Yb3+, replacing isomorphically lanthanum in the La2Zr2O7 with pyrochlore cubic structure, on material photophysical properties was investigated by selective doping, in the molar ratio of Er3+/Yb3+ ranging from 0.5 to 5. The reflectance spectra of materials prepared by sol-gel co-precipitation method after sintering at 1400 °C, investigated in the UV–VIS–NIR range showed as expected well resolved absorptions due to the 4f–4f intra-configurational transitions. At the same time, dielectric properties of sintered samples were investigated by terahertz time domain spectroscopy. The refractive indices observed in the range of ~4.46–5.15, indicate high dielectric permittivity at THz frequencies applicable in energy storage materials or THz communication components. For all samples a broad absorption band was found in the THz region and the band intensities were clearly associated with the doping amount of Er and Yb cations into the La2Zr2O7 structure, at frequencies 0.75–1.02 THz. Significant correlation at the level of R2 = 0.911 was found between the absorption band corresponding to the 4I15/2 → 2H11/2 transition at 520.5 nm and the integrated intensities of THz bands. Dielectric ceramic materials such as titanium-, tantalum- and niobium- oxide based ceramics have permittivity in the range 20–30. The permittivity of studied La2Zr2O7 was ~20 and increased after doping by Er3+/Yb3+ to ~21–26.

Structural, electrical and ferroelectric characteristics of lead-free ceramic: Bi(Fe0.85Gd0.15)O3

Structural and electrical properties of Bi(Fe0.85Gd0.15)O3 ceramics, synthesized via standard solid state reaction technique is reported in this communication. Powder X-ray diffraction analysis reveals the phase transition from rhombohedral to orthorhombic symmetry. The structural study shows the formation of a dense compact high quality sample. The average crystallite size was found to be 38 nm. High dielectric permittivity value is observed with an increasing temperature. Impedance spectroscopy analysis suggests a semiconductor nature and conductivity study confirms the presence of correlated barrier hopping mechanism. The P-E loop study shows an enhancement in remnant polarization. Furthermore, several other interesting features are also reported in this work.

Lead-free high-temperature dielectrics with wide temperature stability range induced from BiFeO3-BaTiO3-based system

Lead-free BNSTNZ ((Bi,Na,Ba,Sr)(Ti,Nb,Zr)O3)-modified BF35BT (0.65BiFeO3-0.35BaTiO3) dielectrics were investigated by conventional solid-state reaction method. Dielectric permittivity of BFBT-BNSTNZ ceramics was suppressed through addition of BNSTNZ content, while dielectric temperature stability range was expanded from 105 °C to 412 °C as BNSTNZ content increases from 0.025 to 0.1, due to the ferroelectric-relaxor phase transition. In particular, x = 0.10 exhibits the widest stability temperature range from 88 °C to 500 °C having small variation of (Δεm/εm150 °C ≤ 15%) with high dielectric permittivity (> 1000) and low dielectric loss (tanẟ ≤ 0.1) in temperature range from 50 °C to 250 °C. Moreover, high room temperature energy storage density (Wstore) of 0.75 and 0.57 J/cm3 with energy storage efficiency (ƞ) of 57% and 78% for x = 0.03 and x = 0.10, respectively, was achieved. These results indicate that BFBT-BNSTNZ can be a promising system for high-temperature dielectric and energy storage applications.

High energy storage capabilities of CaCu3Ti4O12 for paper-based zinc\u2013air battery

Zinc–air batteries proffer high energy density and cyclic stability at low costs but lack disadvantages like sluggish reactions at the cathode and the formation of by-products at the cathode. To resolve these issues, a new perovskite material, CaCu3Ti4O12 (CCTO), is proposed as an efficacious electrocatalyst for oxygen evolution/reduction reactions to develop zinc–air batteries (ZAB). Synthesis of this material adopted an effective oxalate route, which led to the purity in the electrocatalyst composition. The CCTO material is a proven potential candidate for energy applications because of its high dielectric permittivity (ε) and occupies an improved ORR-OER activity with better onset potential, current density, and stability. The Tafel value for CCTO was obtained out to be 80 mV dec−1. The CCTO perovskite was also evaluated for the zinc–air battery as an air electrode, corresponding to the high specific capacitance of 801 mAh g−1 with the greater cyclic efficiency and minimum variations in both charge/discharge processes. The highest power density (Pmax) measured was 127 mW cm−2. Also, the CCTO based paper battery shows an excellent performance achieving a specific capacity of 614 mAh g−1. The obtained results promise CCTO as a potential and cheap electrocatalyst for energy applications.

Study of microstructural and electrical properties of silver substituted hydroxyapatite for drug delivery applications

Silver doped hydroxyapatites (Ag-HAp) [Ca10−xAgx(PO4)6(OH)2;(0.0 ≤x ≤ 1.0)] were synthesized with pH = 10, by the in-situ hydrothermal method. Structural, microstructural, compositional, electrical and biocompatibility properties of Ag-Hap samples were studied to ascertain the suitability of the experimental samples in drug-delivery applications. The Rietveld refinement of the X-ray diffraction (XRD) pattern, analysis of Fourier transform infrared (FTIR) spectra, X-Ray photoelectron (XPS) spectra, and Energy Dispersive X-Ray (EDAX) spectra of the Ag-HAp samples had confirmed the successful doping of Ag atoms in the HAp lattice and simultaneous growth of secondary β-TCP phase with the detailed chemical phase compositions of appropriate percentages. The Field Emission Scanning Electron Microscopy (FESEM), EDAX, and Brunauer–Emmett–Teller (BET) characterizations were carried out to study their morphological, compositional, surface, and porous behavior. The cytocompatibility of the laboratory-synthesized biomaterials with sensitive human embryonic kidney cells (HEK293) by in-vitro MTT assay testing revealed that the Ag-HAp powders had no toxic effect on living body-cells up to the safe limit of usage (≤15 μg/mL). The relative cell-viability percentage (%rcv) was evaluated to be 95–106% for highly doped samples. The incorporation of monovalent Ag ions within HAp lattice influenced the thermal hopping of the charge carriers and resulted in significantly high ionic conductivity with very low activation energy for higher temperatures. The significantly high dielectric permittivity for elevated temperatures (613 K) of the Ag-HAp compared to that of pure-HAp, and the considerable amount of interfacial polarization occurring within highly-conductive grain (~10−5Sm−1) and resistive grain-boundary as established by complex impedance study gave rise to the probability of occurrence of the quasi-permanent surface potential with promising specific surface area (~40 m2/g). The highly biocompatible Ag-HAp rods, with good dielectric and electrical properties, showed a huge possibility of the material being used as a nano-carrier for electric field-induced targeted drug delivery purposes in the future.

Flexible and high dielectric permittivity composites of Na1/3Ca1/3Bi1/3Cu3Ti4O12 and vinylidene fluoride‐trifluoroethylene copolymer (P[VDF‐co‐TrFE

AbstractFlexible composites formed by the perovskite Na1/3Ca1/3Bi1/3Cu3Ti4O12 (NCBCTO) with a copolymer of PVDF with TrFE (P[VDF‐co‐TrFE]) and three phases composites made of NCBCTO, P(VDF‐co‐TrFE), and multiwall carbon nanotubes (MWCNT) were successfully prepared by solution casting with ultrasound. Their structures were analyzed by wide angle x‐rays diffraction (XRD), Fourier Transform infrared (FTIR), and Raman spectroscopy, while their morphology and thermal properties were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The dielectric properties were measured by impedance spectroscopy. All the composites developed predominantly the β‐phase; in some of them, the NCBCTO acted as a β‐phase nucleating agent, increasing its amount. The addition of NCBCTO altered the Curie temperature of the PVDF‐TrFe composites, indicating suppression of the CL‐phase. The best combination of high dielectric permittivity with low dielectric loss was displayed by the composite with 75 wt% of NCBCTO and 25 wt% of P(VDF‐co‐TrFE). The MWCNTs did not contribute to the increase of permittivity, which was attributed to its poor dispersion; instead of behaving as the electrodes of a capacitor, the MWCNT formed a conductive path, probably due to the impeding presence of the NCBCTO particles.

High-gain and low-profile dielectric-image-line leaky-wave-antenna for wide-angle beam scanning at sub-THz frequencies

A low-profile THz leaky-wave antenna (LWA) enabled by a Dielectric Image-Line (DIL) with wide beam steering capability is reported for the first time in this paper. The DIL as a low-loss dielectric waveguide synthesized directly on a substrate with high dielectric permittivity is an appropriate candidate for emerging directive compact antennas for future sub-THz wave communications. The dominant mode of DIL is disturbed by printing two periodic set of radiating elements on the top wall of DIL, including three barrier strips and two anti-reflection strips with an extensive tuning range for open stop-band (OSB) suppression. The operation bandwidth of the proposed antenna spans from 142 GHz to 225 GHz providing an impedance bandwidth of 48.8% in the fast wave region. It is observed from numerical simulations that the proposed 35-cell leaky wave antenna permits a beam steering angle of 128° (−68° to 60° (including the broadside)) in the operation frequency band with the gain varying from 14 to 19.3 dBi in the fast wave region. Detailed design guidelines along with simulation results are presented. The proposed antenna has the capability of being directly scaled to other frequency bands by considering its corresponding dispersion characteristic.

High dielectric permittivity and dielectric relaxation behavior in a Y2/3Cu3Ti4O12 ceramic prepared by a modified Sol−Gel route

In this work, Y2/3Cu3Ti4O12 ceramics were fabricated via a modified sol−gel route. Structural, dielectric, and electrical parameters were systematically investigated. The XRD results indicate that a CaCu3Ti4O12 phase (JCPDS No. 75–2188) is present in every sintered sample. SEM images of Y2/3Cu3Ti4O12 ceramics disclose a fine-grained ceramic microstructure. Interestingly, high dielectric permittivity, ∼6600–7600, with loss tangents of ∼0.918–1.086 were achieved in the sintered Y2/3Cu3Ti4O12 samples. Density functional theory (DFT) calculations were used to investigate the most stable structure of the Y2/3Cu3Ti4O12 ceramics. Our DFT results reveal that two calcium vacancies (VCa) are isolated from each other. We also determined the lowest energy configuration of an oxygen vacancy (VO) in the Y2/3Cu3Ti4O12 ceramics occurred during the sintering process. We found that the VO is trapped close to the Y atom in this structure. Both computational and experimental studies specify that the oxygen vacancy is located close to the Y atom in the Y2/3Cu3Ti4O12 lattice and it might be a bivalent oxygen vacancy. As a result, due to charge balance, charge compensation of the transition ions, i.e., Cu and Ti ions, might take place. The charge compensation mechanisms in the Y2/3Cu3Ti4O12 lattice were verified using an XPS technique. Impedance spectroscopy confirms the presence of an inhomogeneous microstructure consisting of semiconducting grains and insulating grain boundaries in the sintered Y2/3Cu3Ti4O12 ceramics. This electrical result is consistent with the computational analysis, showing that a charge compensation mechanism might be involved in generation of the grains' semiconductive region due to the presence of a VO. Consequently, high dielectric permittivity in Y2/3Cu3Ti4O12 may have originated from an internal barrier layer capacitor (IBLC) effect.

Triple-doping of (Ga1/2Nb1/2)xTi1-xO2 ceramics with Al3+ for enhanced giant dielectric response with simultaneous decrease in dielectric loss

An acceptor-donor co-doped (Ga1/2Nb1/2)0.1Ti0.9O2 ceramic is triple-doped with Al3+, followed by sintering at 1450 °C for 5 h to obtain (AlxGa1/2-xNb1/2)0.1Ti0.9O2 ceramics with improved giant dielectric properties. Homogeneous dispersion of all dopants inside the grains, along with the partially segregated dispersion of the Ga3+ dopant along the grain boundaries, is observed. The (AlxGa1/2-xNb1/2)0.1Ti0.9O2 ceramics exhibit high dielectric permittivities (ε′∼4.2–5.1 × 104) and low loss tangents (tanδ∼0.007–0.010), as well as a low-temperature coefficients (<±15%) between − 60 and 200 °C. At 1 kHz, tanδ is significantly reduced by ∼4.4 times, while ε′ is increased by ∼3.5 times, which is attributed to the higher Al3+/Ga3+ ratio. The value of tanδ at 200 °C is as low as 0.04. The significantly improved dielectric properties are explained based on internal and surface barrier-layer capacitor effects, which are primarily produced by the Ga3+ and Al3+ dopants, respectively, whereas the semiconducting grains are attributed to Nb5+ doping ions.

Effects of Electron-Beam Radiation on the Dielectric Properties of PVA/xNiO Nanocomposite for Energy Storage Applications

For energy storage applications, a material that has high dielectric permittivity, low loss factor, strong thermal resistance, easy processability, and low cost is highly desirable. In the present study, PVA/xNiO nanocomposite films with different NiO contents of (0, 10, and 50) wt% were prepared by casting technique. The PVA/xNiO of 50 wt% NiO has been irradiated with 3 MeV electron beam at a dose of 50 kGy at room temperature in order to investigate the modifications induced in its dielectric properties. The results show that the NiO nanoparticles are well incorporated inside the PVA matrix and the crystallite size of NiO has been decreased upon doping by 50 wt% NiO from 15.45 to 11.44 nm. Also, PVA/(50%)NiO nanocomposite shows indirect allowed optical transition (3.43 eV) with relatively high dielectric constant (7.60 to 9.55) and low loss factor (<0.1) at high frequency (1 MHz) and the entire indicated range of temperature which proposes to use this material in energy storage applications. The electron beam radiation has increased the dielectric constant (10.52 to 13.94) which is preferable. However, a slight increase is observed in the loss factor (<0.109).

Significant Reduction of Resonant Frequency by Multi-Layered Dielectric Material-Loaded Coaxial Cavity for Microwave Heating

This paper presents a microwave heating method using a cavity whose size is much smaller than the free-space wavelength. The resonant frequency was reduced by inserting multi-layer dielectrics into the cavity, and an appropriate mode was generated in the cavity to heat a specific area inside it. High-permittivity dielectrics were used to make the cavity resonate in the frequency range of a few gigahertz. A formula for the resonant frequency of the multi-layer dielectric material-loaded cylindrical cavity was analytically derived. The frequency reduction by using a dielectric-loaded cylindrical cavity geometry was predicted from the derived formula, from 12.2 GHz to 4.6 GHz, whereas the experiment results showed a reduction from 10.8 GHz to 4.5 GHz. The analytical and the experiment results were compared and analyzed with simulations, which showed good agreement. The heating efficiency at the target in the multi-layered dielectric geometry was analyzed. The electric field inside the target material was measured to prove the temperature response of the microwave heating and was compared with the simulation result. This paper confirms a technical possibility of microwave heating of a smaller-sized cavity with an insertion of low-loss dielectric material in the vicinity of a heating target.

Giant dielectric properties of Mg doped CaCu3Ti4O12 fabricated using a chemical combustion method: Theoretical and experimental approaches

In this work, CaCu3-xMgxTi4O12 (x = 0, 0.05, and 0.10) ceramics were successfully prepared via a chemical combustion method. No impurity phase was detected in these two ceramics. Fine−grained microstructures were formed in all CaCu3-xMgxTi4O12 ceramics. Interestingly, high dielectric permittivities of ∼6.58 × 103 − 2.87 × 104 with low loss tangents of ∼0.011 − 0.025 were obtained in the Mg-doped CaCu3Ti4O12 ceramics. According to the electrical measurements, improved dielectric properties in the doped ceramic samples were a result of an enhanced grain boundary response. To elucidate the electronic structure of CaCu2.90Mg0.10Ti4O12, first-principles calculations were carried out. It was found that two Mg atoms preferentially interact. Moreover, by adding an oxygen vacancy into the CaCu2.90Mg0.10Ti4O12 structure, our results revealed that it was likely to be isolated from the Mg atoms, indicating an oxygen loss suppression during the sintering process. This resulted in an enhanced grain boundary resistance in the CaCu2.90Mg0.10Ti4O12 ceramic. Based on both the experimental and computational studies, the internal barrier layer capacitor (IBLC) model was found to be the primary origin of the colossal dielectric response in all CaCu3-xMgxTi4O12 ceramics examined in the current study.

Peano‐Hydraulically Amplified Self‐Healing Electrostatic Actuators Based on a Novel Bilayer Polymer Shell for Enhanced Strain, Load, and Rotary Motion

The hydraulically amplified self‐healing electrostatic actuator is an emerging driving component for soft robotics, which is composed of a flexible dielectric polymer shell that is partially covered by conductive electrodes and filled with a liquid dielectric. However, the low permittivity and dielectric strength of the polymer shell remain a challenge that limits the actuator performance. Herein, a Peano‐hydraulically amplified self‐healing electrostatic actuator is constructed by innovatively integrating a bilayer polymer shell for combined favorable properties of high dielectric strength, dielectric permittivity, and elastic modulus. Compared with a traditional single‐layer shell actuator, the new bilayer actuator architecture generates an increased strain (164%) at 5 kV and improves load‐bearing capability (620 mN) at 6 kV, thereby providing a significantly enhanced actuation performance. The new actuator is further applied in driving a ratchet system, which converts the reciprocating motion of the actuator into a rotating motion and a flexible output torque, in order to protect the rotating components from impact. The high strain and load characteristics of the bilayer configuration and the easy‐to‐deform characteristics of the new actuator design make it an attractive approach to fabricate complex geometries and achieve a variety of motion modes in soft systems.

Microwave assisted processing of X8R nanocrystalline BaTiO3 based ceramic capacitors and multilayer devices

BaTiO3 based multilayer ceramic capacitor (MLCC) is an important component in electronic devices. Achieving high dielectric performance, miniaturisation and cost effectiveness are still challenging. Co-sintering ceramic layers with metal electrodes and use of expensive Pt and high-Pd content compositions as electrodes are other key issues. Thus, the major factors that could lead to cost effectiveness of MLCCs are reduction in sintering temperature and using less expensive metal electrodes without compromising dielectric performance and these traits could auger well for the next generation low-cost high performance electroceramic devices – this is the subject matter of the present study.In this work, initially we have fabricated and analysed the dielectric performance of BaTiO3 (BT) ceramics with different BT particle sizes (50 nm, 100 nm and 200 nm). Based on results, 200 nm BaTiO3 was used for further studies due to its superior dielectric performance. Then, to reduce the sintering temperature and improve the dielectric performance of 200 nm BaTiO3 ceramics, Bi2O3 was used as a dopant which acts both as a sintering aid and helps to improve the dielectric performance. A combination of rare earth dopant system (proprietary from the industrial partner Knowles, UK) with Bi2O3 was also added to tune the defect chemistry of BaTiO3 for enhancement in dielectric performance further. A homogeneously mixed BT-based ceramic slurry system (containing the above dopants) with optimum rheology was developed using a non-aqueous medium, dispersant and a binder system. Addition of glass frits for lowering the sintering temperature and its effect on dielectric performance was also investigated on both discs (made using dry pressing of the powders obtained via drying of the slurry) as well as multilayer ceramic capacitors (MLCCs) fabricated through screen printing. Conventional, microwave and hybrid sintering procedures were employed for the densification of the electroceramic devices and these were characterized for density, microstructure, composition and dielectric performance systematically. Conventional sintering resulted in undesired large micron sized surface features which are detrimental to device durability, whereas formation and growth of these features have been demonstrated to be significantly minimised using the rapid microwave assisted sintering procedures for the first time. Further efficient co-sintering of ceramic layers with less expensive (Ag/Pd) alloy has also been accomplished using the microwave methodology. The resultant BaTiO3 based capacitive devices exhibited high dielectric permittivity, superior X8R performance and low dissipation factor, asserting their massive potential for widespread high temperature applications in automotive, sensing and space sectors.

Novel lead-free BCZT-based ceramic with thermally-stable recovered energy density and increased energy storage efficiency

The eco-responsible lead-free piezoelectric ceramics have been intensively searched for more than a decade, however, the final goal to replace toxic ceramics like lead zirconate titanate (PZT) with lead-free compounds, having comparable or even better performance has not yet been reached. In this road, the lead-free ceramics Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT), possessing excellent dielectric, ferroelectric, and piezoelectric properties are regarded as serious candidates for the PZT replacement. Besides, nanostructuring BCZT is of paramount importance to enhance these functionalities even more. Here, BCZT multipodes are designed by template-growth hydrothermal synthesis using hydrogen zirconate titanate nanowires. We demonstrate that the fabricated BCZT multipodes exhibit high dielectric permittivity of 5300 with a temperature stability coefficient of ±5.9% between 20 and 140 °C. A significant recovered energy density of 315.0 mJ/cm3 with high thermal stability and high energy storage efficiency of 87.4%, and enhanced large-signal piezoelectric coefficient d33∗ (310 pm/V) are found. Compared to the traditional BCZT ceramics reported in the literature, relying on high-temperature processing, our sample exhibits boosted energy storage parameters at a much lower temperature. These outcomes may offer a new strategy to tailor eco-responsible relaxor ferroelectrics toward superior energy storage performance for ceramic capacitor applications.

Synthesis and dielectric properties of K1.6Fe1.6Ti6.4O16 ceramics produced by the Pechini method

Potassium titanate modified with Fe3+ ions matching the stoichiometry of K1.6Fe1.6Ti6.4O16 (KFTO) was obtained by the polymer complex precursor method (Pechini method). The phase composition and morphology of the obtained sample were characterized using XRD, laser diffraction, and SEM technique. X-ray phase analysis shows single-phase formation of potassium titanate with a tetragonal hollandite-like structure. The Rietveld method was used to clarify the crystal lattice parameters. The parameters of the crystal lattice are: a = b = 10.1510 Å и c = 2.9659 Å. The results of SEM and laser diffraction showed that the particles of the studied nanopowder have a cubic shape and an average size of 400 nm. The dielectric properties in the frequency range of 0.1 Hz to 1.0 MHz were studied for ceramic disks obtained by sintering of compressed nanopowder at 1080 oC. It was found that ceramics based on KFTO solid solutions have high dielectric permittivity and low dielectric losses and characterized with increased polarizability. The high polarizability of the material is explained by the relatively high mobility of K+ ions in the tunnel of the considered hollandite structure that is accompanied by the redistribution of electrons in the crystal lattice. A discussion of the contribution of various processes to the permittivity is presented.

A low-concentration sulfone electrolyte enables high-voltage chemistry of lithium-ion batteries

Commercial carbonate electrolytes with poor oxidation stability and high flammability limit the operating voltage of Li-ion batteries (LIBs) to ~4.3 V. As one of the most promising candidates for electrolyte solvents, sulfolane (SL) has received significant interest because of its wide electrochemical window, low flammability and high dielectric permittivity. Unfortunately, SL-based electrolytes with normal concentrations cannot achieve highly reversible Li+ intercalation/deintercalation in graphite anodes due to an ineffective solid electrolyte interface, thus undermining their potential application in LIBs. Here, a low-concentration SL-based electrolyte (LSLE) is developed for high-voltage graphite||LiNi0.8Co0.1Mn0.1O2 (NCM811) full cells. A highly reversible graphite anode can be achieved through the preferential decomposition of the dual-salt LiDFOB-LiBF4 in the LSLE. The addition of fluorobenzene further restrains the decomposition of SL, endowing uniform, robust and inorganic-rich interphases on the electrode surfaces. As a result, the LSLE with improved thermal stability can support the MCMB||NCM811 full cells at 4.4 V, evidenced by an excellent cycling performance with capacity retentions of 83% after 500 cycles at 25 ℃ and 82% after 400 cycles at 60 ℃. We believe that the design of this fluorobenzene-containing LSLE offers an effective routine for next-generation low-cost and safe electrolytes for high-voltage LIBs.