A method for forming electrode structured microsystems based on titanium foil was developed. These microsystems can be used in electrochemical energy storage devices. The method includes a three-stage chemical treatment of the titanium foil surface: etching in concentrated HCl to create a microrelief, processing in the aqueous solution of KOH to form a layer of potassium polytitanate and the subsequent modification in the solution of manganese sulfate with the following heat treatment at 750°C. Using the SEM and XRD methods, it was shown that the coating, obtained by the chemical and heat treatment, consists of submicron particles of hollandite-like solid solution of KxMnyTi8−yO16 that filled the pits on the surface of titanium which were formed by acid etching. Electrochemical studies (cyclic voltammetry) in a three-electrode cell (electrolyte – 5% aqueous KCl solution) showed that the synthesized hybrid electrode materials have a significantly higher specific capacity (up to 3.2 F/cm2 ) compared with the electrodes treated only with acid and alkali (0.22 F/cm2 ) and raw titanium (∼1 F/cm2 ). The high cyclic stability of the obtained electrodes was demonstrated.

The work presents a comparative cyclic voltammetry analysis of all-solid-state mock-up cells based on potassium polytitanate. Most measurements were carried out at 25°C. Potassium polytitanate sample with 10 wt.% of phosphotungstic acid was studied at 0°C, followed by the Arrhenius estimate of its characteristics at 25°C. The study focuses on comparing integral capacitive characteristics, response stability at different scan rates and charge storage mechanisms determined using the Dunn and Trasatti methods. Additionally, the anodic and cathodic contributions to capacitance as indicators of reversibility, branch symmetry and kinetic non-equivalence between charge accumulation and release are examined. The combined use of total capacitance, surface-controlled and diffusion-limited contributions, outer and inner charge and Ca/Cc ratio makes it possible to identify the most promising all-solid-state cell configurations as well as to determine the samples which provide the best capacitance response and those with a higher rate stability and reversibility.

The electrochemical properties of a ceramic composite material in which a hollandite-like potassiumchromium titanate solid solution is presented as the main phase were studied using impedance spectroscopy. The dependences of the conductivity of the obtained composites on temperature in the range from 250 to 800°C were studied. The activation energies of volumetric, intergranular and grain volume conductivity were determined. The phase composition of the material and the crystallographic structures of individual phases were also established.

This paper presents a model of an electrode material for a hybrid capacitor and experimentally confirmed ways to improve cell parameters, such as increasing the energy capacity of the cell; increasing the operating voltage in cells with aqueous electrolyte up to 2.6 V, twice the water decomposition potential; and reducing internal resistance. The technology of manufacturing electrode materials for hybrid capacitors is also presented, and its choice is justified.

The fluorine-containing fluorite-like compounds of composition NaLn 4 Mo 3 O 15 F (Ln = La, Pr, Nd) are produced using the method of solid-phase synthesis in air. Their thermomechanical and conducting properties, as well as hygroscopicity, are studied. It is confirmed that the synthesized specimens are isostructural to the cubic compounds Ln 5 Mo 3 O 16 with the fluorite-like structure. It is shown that in the temperature range of 20–600°C, the specimens of NaLn 4 Mo 3 O 15 F (Ln = La, Pr, Nd) expand linearly, and their thermal expansion coefficients (13–14) × 10 –6 K –1 are close to the coefficients of conventional SOFC electrolytes, for example, YSZ. Using the thermal gravimetric analysis, it is shown that the weight loss of the studied specimens in the range from 30 to 700°C is caused by their hygroscopicity. The electrophysical properties of the compounds are studied using the method of impedance spectroscopy in the humid atmosphere, and the proton component of conductivity is revealed.

Experimental studies of the electrochemical and electrophysical properties of protonated potassium polytitanate and sodium-modified pryderite were carried out using the method of nonlinear impedance spectroscopy. The frequency dependencies of the resistance of the volume of grains and grain boundaries were determined depending on the magnitude of the polarization voltage (DC) and on the value of the perturbation signal (AC).

The electrochemical and electrophysical properties of basic and protonated potassium titanates in contact with the graphite electrodes were studied using the method of impedance spectroscopy. The characteristics of potassium titanates are given depending on the methods of modification and on the methods of their processing. The activation energies for some compositions were determined.

The electrochemical and electrophysical properties of the protonated and modified with silver iodide potassium titanates, which can be applied in energy storage units, have been investigated by impedance spectroscopy. It has been shown that the dielectric losses at medium and high frequencies are weakly dependent on the polarizing voltage. It has also been established that transfer in modified potassium titanate can be made through potassium and silver ions. The equivalent scheme of the process has been proposed and the magnitudes of the Warburg impedances have been calculated.

In this paper, the electrochemical and electrophysical properties of protonated potassium polytitanate synthesized at pH values varying from 3.11 to 8.88 depending on the magnitude of the polarization voltage and the magnitude of the measured signal were studied by the method of impedance spectroscopy. The values of effective conductivity, relaxation times, frequency dependences of the loss tangent, and dielectric permittivity are determined.

The new materials obtained in the potassium polytitanate (PPT)–MnSO4 system by modifying PPT in aqueous solutions of manganese sulfate of various concentrations, followed by thermal treatment and annealing at 1080°C, were synthesized and studied. The phase composition of the obtained materials was determined. Their electrochemical and electrophysical properties in the temperature range from 250 to 700°C were studied. The maximum volumetric and intergranular conductivities of the obtained materials were observed at 250°C (9 · 10−4 and 6 · 10−4 S/cm, respectively) in the samples containing 25 wt.% MnO. The value of the activation energy of the conductivity in the volume of grains and grain boundaries was 0.37 and 0.45 eV, respectively. It was shown that the permittivity at the frequency of 1 kHz varies from 103 to 5 · 105 depending on the temperature and manganese oxide content.

Cubic, tetragonal, and monoclinic (Bi2O3)(x) (Nd2O3)(y) (WO3)(z) (x + y + z = 1) solid solutions based on the Bi2O3 oxygen ion conductor have been prepared by solid-state reactions in the ternary system Bi2O3-Nd2O3-WO3. The field of monoclinic compounds with a Bi3.24La2W0.76O10.14-type structure has been shown to account for most of the ternary system. Compounds with a cubic fluorite structure exist at the boundary of the monoclinic phase field in two small regions at high (83-91 mol% Bi2O3, delta-phase) and low (20-55 mol% Bi2O3, delta'-phase) Bi concentrations. The cubic samples of the delta-phase retain their structure only during rapid heating and cooling, but annealing in the range of 300-700 degrees C results in structure degradation to lower symmetry phases. The monoclinic compounds and Bi-poor cubic compounds (delta'-phase) have good thermal stability. The cubic samples of the delta'-phase are hygroscopic. Their bulk conductivity noticeably increases with atmospheric humidity, suggesting that these materials are potential proton conductors.

The paper considers the electrochemical properties of potassium polytitanate synthesized at the values of pH varying from 3 to 8 in a wide temperature range from −26 to +80°C. The conductivity values and the activation energy were determined with the help of the method of impedance spectroscopy. The application of the obtained material used as a ceramic solid electrolyte in the energy storage units operating at low temperatures in the Far North is considered in the article.

An experimental method to produce a new kind of functional nanocomposite materials is proposed. The synthesis involved the treatment of layered potassium polytitanate with ternary aqueous solutions of Me2+(Zn) and Me3+(Al, Cr) nitrates and K2CO3; the products were characterized by XRD, SEM, TEM and laser diffraction methods. The structure of the particles produced is formed by platy quasi-amorphous lepidocrocite-like flakes of potassium polytitanate with incrusted nanoparticles of layered double hydroxides of Zn4Cr2(OH)12CO3∙3H2O or Zn0.66Al0.34(OH)2(CO3)0.17∙H2O. The measured physico-chemical, tribological and electrical properties of the nanocomposites are discussed taking into account their potential application as antifriction and antiscuff additives of lubricating compositions or functional materials in the manufacture of electronic devices, emphasizing the influence of their structural features on the tribological and electrical properties.

We have studied the formation, polymorphism, and electrical conductivity of Bi2O3-based compounds with the general formula (Bi2O3)(x)(Nd2O3)(y)(MoO3)(z) (x + y + z - 1) in the ternary system Bi2O3-Nd2O3-MoO3. It has been shown that the system contains Bi2O3-based solid solutions with cubic, tetragonal, monoclinic, and rhombohedral structures, depending on composition. Bi2O3-based compounds with the cubic fluorite structure have been identified in two broad composition regions: 0.56 <= x <= 0.9, 0.03 <= y <= 0.22, 0.03 <= z <= 0.23 and 0.36 <= x <= 0.6, 0.25 <= y <= 0.47, 0 <= z <= 0.21. In addition, a large region of tetragonal compounds has been detected, with 0.37 <= x <= 0.56, 0.19 <= y <= 0.38, and 0.23 <= z <= 0.33. The conductivity of the samples studied increases with Bi2O3 concentration: from 0.01 ((Bi2O3)(0.36)(Nd2O3)(0.45)(MoO3)(0.19) sample) to 0.7 S/cm ((Bi2O3)(0.9)(Nd2O3)(0.07)(MoO3)(0.03) sample) at 800 degrees C. The cubic and tetragonal symmetries of the samples persist after rapid heating and cooling, but prolonged annealing in a limited temperature range can lower the symmetry of some samples. Heating the samples to above their instability range restores their original structure and properties. In addition, we have identified (Bi2O3)(x)(Nd2O3)(y)(MoO3)(z) compounds that remain stable, without symmetry changes, at any temperature, even at long annealing times. (C) 2019 Elsevier B.V. All rights reserved.

The synthesis of new materials for supercapacitors is considered. Alloying of active dielectrics based on potassium polytitanates yields nanohybrids with specified properties and high dielectric permittivity. These materials are suitable for the construction of a new generation of supercapacitor structures.

The manifestation of piezoelectric resonances in high-resolution impedance spectra was found and interpreted using the example of KDP crystal. A resonance signal inversion was observed in LiIO 3 crystals, having significant ion conductivity.

AbstractThe manifestation of piezoelectric resonances in high-resolution impedance spectra was found and interpreted using the example of KDP crystal. A resonance signal inversion was observed in LiIO_3 crystals, having significant ion conductivity.