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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, δ-phase) and low (20–55 mol% Bi2O3, δ′-phase) Bi concentrations. The cubic samples of the δ-phase retain their structure only during rapid heating and cooling, but annealing in the range of 300–700 °C results in structure degradation to lower symmetry phases. The monoclinic compounds and Bi-poor cubic compounds (δ′-phase) have good thermal stability. The cubic samples of the δ′-phase are hygroscopic. Their bulk conductivity noticeably increases with atmospheric humidity, suggesting that these materials are potential proton conductors.

Iron-doped potassium titanate with a hollandite structure is synthesized by the solid-phase method. To reduce the contact resistance and to increase the diffusion coefficient of potassium ions, a conductive carbon coating is applied to the surface of the titanate synthesized in an argon atmosphere. The formation of the composite material is confirmed by the results of X-ray phase analysis, scanning electron microscopy, and IR spectroscopy. The half-cells with potassium metal in a CR2025 case, which are assembled on the basis of the synthesized composite, are tested electrochemically with subsequent calculation of the specific capacitance, power density, and energy density. It is found that the specific capacitance of an electrode with a carbon coating is 10–15% higher with low sweep rates (1 and 3 mV s–1). It is shown that the use of carbon coatings increases the diffusion coefficient of potassium to 1.77 × 10–14 cm2 s–1/2.

Multilayer graphene oxide was synthesized by anodic oxidation of dispersed graphite, and the efficiency of its use as an electrode material for a supercapacitor was shown. In an alcohol suspension, the thickness of multilayer graphene oxide particles is less than 0.1 μm with an area of more than 100 μm2. The multilayer graphene oxide electrode has a high specific capacity of 107 F g–1 and a high charge retention rate of 97% after 5000 cycles at a current of 2 A g–1. The multilayer graphene oxide electrode demonstrated a maximum specific energy of 8.7 W h kg–1 at a current density of 0.1 A g–1 and a maximum power of 2291.1 W kg–1 at a current density of 4 A g–1. The impedance data at various DC voltages showed that after 5000 cycles, the charge transfer resistance increases by 26%. It was found that multilayer graphene oxide synthesized by the electrochemical method is a promising electrode material for producing a symmetric supercapacitor.

The article investigates the influence of the reduction modes of hollow nickel oxide microspheres synthesized by the pyrolysis of ultrasonic aerosols on the ratio of the oxide and metallic forms of nickel in their structure. The synthesis of microspheres from an aerosol of an aqueous solution of nickel nitrate was carried out; their composition and morphology were studied. The reduction of microspheres was carried out in a stream of hydrogen at different temperatures. The ratio of metallic nickel and oxide was determined by two different methods: according to the data of thermogravimetric analysis and by the Rietveld method based on the results of x-ray phase analysis. It is shown that the proportion of metallic nickel increases with an increase in the reduction temperature to approximately 375°C and then changes insignificantly. The fractional composition of microspheres was determined.

The hollandite-like copper doped potassium titanate was synthesized by two-step method, including the potassium polytitanate precursor modification with copper compounds in aqueous solution and the following calcination at 900 °C. The structure of material obtained was studied using the XRD and SEM analysis. The Rietveld method was used to estimate the crystalline unit cell parameters and calculate the exact stoichiometry of K1.53(Cu0.76Ti7.24)O16 by refining the atomic occupancies for chemical elements. High-k ceramic materials based on this shollandite-like solid solution were sintered at different temperatures varied in the range from 1000 to 1100 °C. The influence of sintering conditions on electric properties of the obtained ceramics was investigated in a wide frequency range. The contribution of different processes on permittivity was discussed using the electron-pinned defect-dipole (EPDD) model, and the internal barrier layer capacitance (IBLC) model. The optimal conditions to produce modified potassium polytitanate, used as intermediate, as well as optimal sintering conditions which allowed obtaining mono-phase hollandite-like ceramic materials were recognized. It was found that such ceramic materials had high permittivity (e’ ≈ 0.9 × 104 at 10 Hz).

High-performance harvesting of waste heat energy and its conversion into electric energy via thermo-electrochemical cells is an essential strategy of renewable energy development. Even though there is a large amount of scientific research available, but due to expensive electrode materials and low efficiency, the thermo-electrochemical cells have not found practical application. Here we demonstrated thermo-electrochemical cell with nickel (Ni) hollow microspheres-based electrodes, provided the highest hypothetical Seebeck coefficient of 4.5 mV/K (for aqueous electrolyte based thermocells) until today and open-circuit voltage values of up to 0.2 V. High values of Seebeck coefficient provide the ability to collect low-temperature heat, and high output potential differences which allow to fabricate batteries for commercial power circuits for various microelectronic devices. This work also proposed a mechanism and science behind the electrode processes, which explains a extremely high values of the hypothetical Seebeck coefficient. This is the first time to use Ni hollow microsphere in thermo-electrochemical cell for heat harvesting and thermal energy conversion into electricity. Because of the low cost of Ni microspheres electrode-based developed thermo cells could be commercially feasible for harvesting low-quality thermal energy.

The effect of a multicomponent polymer binder composition on the electrical conductivity of composites filled with carbon black (CB) is reported. Composites based on a mixture of polypropylene and styrene-ethylene-butylene-styrene (SEBS), plasticized with industrial oil, and filled with electrically conductive CB, were prepared using a twin-roller mixer. The presence of various regions in the volume of the binder and the distributions of CB in binder regions was investigated by scanning electron microscopy. The formation of a special conductive network of CB is observed in the investigated composite. The electrical characteristics of the composites were investigated by means of impedance spectroscopy. On the basis of Raman spectroscopy, it was found that CB is predominantly located in the elastomer (in SEBS plasticized with industrial oil), which forms a continuous phase. It has been shown that the spatial distribution of CB (under constant loading of the filler) can change the conductivity of composites by as much as 5 orders of magnitude, and provides a low percolation threshold.

Thermoelectrochemical cells (thermogalvanic elements, thermo-cells) are the promising devices for sustainably generating electricity from waste heat. These systems directly convert heat into electricity with a performance governed by the properties of the electrode materials and electrolyte. The influence of the nature of electrodes on fundamental properties such as the Seebeck coefficient and power output are investigated in this work. Two different metal electrodes (Zn(s) and Ni(s)) not studied before in the thermogalvanic applications are examined in the ZnSO4 and NiSO4 aqueous solutions respectively, and compared with conventional Cu(s) electrodes (in the CuSO4 solution). It is established that for the copper and zinc electrodes, the experimental values ​​do correspond to theoretical values ​​and are well correlated with the data for similar thermogalvanic cells published earlier. It has been recognized that in the case of the nickel electrode there is a two-step mechanism and extremely high (for aqueous systems), value ​​of the hypothetical Seebeck coefficient (about of 2.83 mV/K with a temperature gradient in the range of 30–60 K) is observed. It is shown that nickel electrode ensures double power output in comparison with previously studied copper one, which makes it highly promising for further research. It is supposed that the effect obtained with Ni electrodes characterized with well-developed surface area allows producing the commercial thermo-electrochemical cells for waste heat harvesting.

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 °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.

Electrical conduction and oxygen diffusion mobility in the bixbyite ( Ia3) and rhombohedral ( R3) polymorphs of the Ln6MoO12-Δ (Ln = Er, Tm, Yb; Δ = δ, δ1, δ2; δ1 > δ2) heavy lanthanide molybdates, belonging to new, previously unexplored classes of potential mixed (ionic-electronic) conductors, have been studied in the range of 200-900 °C. The oxygen self-diffusion coefficient in bixbyite ( Ia3) Yb6MoO12-δ phase estimated by the temperature-programmed heteroexchange with C18O2 was shown to be much higher than that for rhombohedral ( R3) RI (with large oxygen deficiency) and ( R3) RII (with small oxygen deficiency) Ln6MoO12-Δ (Ln = Tm, Yb; Δ = δ1; δ1 > δ2) oxides. According to the activation energy for total conduction in ambient air, 0.99, 0.93, and 1.01 eV in Er6MoO12-δ, Tm6MoO12-δ, and Yb6MoO12-δ bixbyites, respectively, oxygen ion conductivity prevails in the range ∼200-500 °C. Oxygen mobility data for the rhombohedral Ln6MoO12-Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) phases RI and RII indicate that the oxygen in these phases exhibits mobility at much higher temperatures, such as those above 600-700 °C. Accordingly, below 600-700 °C they have predominantly electronic conductivity. As shown by total conductivity study of Ln6MoO12-δ (Ln = Er, Tm, Yb) bixbyites ( Ia3) and rhombohedral phases Ln6MoO12-Δ (Ln = Er, Tm, Yb; Δ = δ1, δ2) ( R3) in dry and wet air, the proton conductivity contribution exists only in Ln6MoO12-δ (Ln = Er, Tm, Yb) bixbyites up to 450-600 °C and decreases with a decreasing of the lanthanide ionic radius. The obtained data on the mobility of oxygen and the presence of proton contribution in bixbyites in the 300-600 °C temperature range make it possible to confirm unequivocally that Ln6MoO12-δ (Ln = Er, Tm, Yb) bixbyites are mixed electron-proton conductors at these temperatures.

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 LiIO3 crystals, having significant ion conductivity.

The samples of ceramic materials based on potassium polytitanate (PPT) characterized with various TiO2/K2O molar ratio, are produced by calcination at 900 °C and investigated. AC conductivity (σac) of the obtained ceramics is measured at different temperatures between 200 and 800 °C in frequency range of 0.1 Hz–1 MHz. The method of combined impedance and modulus spectroscopy is used to analyze the obtained results. The activation energies of DC conductivity, bulk and grain-boundary conductivity as well as relaxation frequency for studied composites are estimated. Using the correlated barrier hopping (CBH) model, the energies of potential barrier between neighboring defect sites for all kinds of investigated materials are presented. The bulk and grain boundary parameters of the produced ceramic materials based on potassium polytitanates are calculated. The mechanism of different vacancies formation in the investigated ceramic system is discussed. The influence of precursor chemical composition on electrical properties for the ceramic composites based on potassium polytitanates is studied.

A highly electrical conductive multi-walled carbon nanotubes based polymer composite is fabricated by iodine doping. Selective localization of carbon nanotubes in polymethyl methacrylate was obtained by intensive dry mixing of polymer and nanotubes powders followed by hot pressing. The electrical conductivity of the materials was significantly increased (10–100%) when the composites were treated with iodine by the gas phase. The electrical conductivity of the materials was significantly increased because of MWCNTs addition from the value not higher than about 10−15 to about 10−2 S/cm. The addition of iodine leads to an additional increase in electrical conductivity by 10–100%, depending on the content of MWCNTs. It is interesting to note that a more effective increase in electrical conductivity is observed at low MWCNTs concentrations. An interesting result of the work is the presentation of the fact that iodine is uniformly absorbed in the bulk of the composite filled with nanotubes; in the case of an unfilled polymer, iodine is deposited only on the sample surface. The percolation nature of the conductivity of the investigated composites was found and the percolation threshold was calculated. It was shown that the percolation threshold does not significantly change after iodination. Thus, in this work, we have shown the possibility of simple technology for producing composites with a spatial localized distribution of carbon nanotubes, providing high conductivity (2.86 × 10−2 S/cm) and a low percolation threshold (about 0.37% vol.) at the MWCNTs content of 1.55% vol.

In the present work, the effect of carbon nanotubes (CNTs) addition on the electrical conductivity and mechanical properties of thermoplastic polymers was investigated. CNTs were incorporated into the polymer matrix either in high concentrations (masterbatch) or as an additive in small quantity (dilution source of masterbatches in a polymeric binder). Masterbatches containing a 5–20% by weight of CNTs and composites obtained through their addition in polypropylene - the actual content of CNTs in polymer 0.1 and 0.01 wt% - were synthesized and characterized by mechanical tests and scanning electron microscopy. Also, the frequency dependence of the AC electrical conductivity of masterbatches and dilute composites were measured. It has been shown that the introduction of masterbatches containing 10 wt% of CNT provides a more efficient reinforcement of the composite than those using masterbatches with 5 and 20 wt% of CNTs. It is also found that the alternating current (AC) conductivities display two or three regions: regions of constant conductivity and regions where the conductivity increases with increasing frequency (following the percolation scaling law). It was also observed that the conductivity increases drastically with increasing CNT content in the investigated concentration range (from 0 to 20 wt%).

Powdered ceramic composites based on the amorphous potassium polytitanate modified in aqueous solutions of cobalt sulfate and calcined at 700℃ (PPT-Co) were used as the ceramic filler of the polytetrafluorethylene–matrix composite dielectrics characterized with high permittivity and low dielectric losses. The influence of the ceramic filler content on the electrical properties of the produced composites was investigated in the range of 1–50 wt%. The obtained results were compared with the data reported in literature for other ferroelectric composites based on polytetrafluorethylene and were analyzed taking into account some theoretical models earlier proposed for the two-component systems. An influence of the temperature on the frequency dependence of permittivity at 30–150℃ for the composites with different filler contents was investigated.

The ternary system Bi 2 O 3 –La 2 O 3 –MoO 3 is shown to contain a wide range of (Bi 2 O 3 ) x (La 2 O 3 ) y (MoO 3 ) z ( x + y + z = 1) compounds isostructural with the cubic phase δ-Bi 2 O 3 , stable at room temperature: 0.65 ≤ x ≤ 0.93. In addition, the ternary system contains two tetragonal phases (β at x = 0.96 and β′ in the region 0.50 ≤ x ≤ 0.61, 0.14 ≤ y ≤ 0.21, and 0.22 ≤ z ≤ 0.31) and a rhombohedral phase in a narrow composition range (0.60 ≤ x ≤ 0.64) on the Bi 2 O 3 –La 2 MoO 6 join. When heated to 1000–1100 °C, the rhombohedral and β′ tetragonal compounds undergo one phase transition, to the cubic phase with the δ-Bi 2 O 3 structure. The samples with the β-Bi 2 O 3 structure exhibit a more complex polymorphism. The electrical conductivity of the samples increases with Bi 2 O 3 concentration. The conductivity of the cubic materials with x = 0.8 reaches 0.6 S/cm at 800 °C. The high-temperature (350–800 °C) conductivity of such samples follows the Vogel–Fulcher–Tammann law. At lower temperatures, their conductivity exhibits Arrhenius behavior with an activation energy near 0.8 eV.

The ionic and electronic conductivity of composite materials based on phosphotungstic acid and polyvinyl alcohol was determined in relation to the concentration of potassium polytitanate (PPT) additive. It was shown that the addition of PPT nanoparticles significantly reduces both the hardening time of the composite material and its electronic conductivity while maintaining high ionic conductivity.

Features are studied for sintering materials prepared by semidry compaction using potassium polytitanate as a precursor powder, modified with cobalt compounds and given preliminary heat treatment at 700°C. Phase composition, thermomechanical and electrophysical properties of ceramic specimens synthesized at 700, 950, and 1100°C are studied. The mechanism of processes occurring during sintering the ceramic studied at different temperatures and its effect of ceramic properties is studied. It is shown that at 700°C optimum properties are exhibited by ceramic specimens sintered below 750°C. The possibility is considered of using ceramic of this type within the composition of thermoelectric and thermoelectrochemical units intended for energy accumulation from dissipated heat of metallurgical production furnace equipment.

Technologies harvesting and converting the heat of low-temperature sources into electricity are one of the current trends in modern renewable energy. Thermoelectrochemical cells based on a nickel oxide electrode are gaining increasing popularity among researchers due to the high values of the hypothetical Seebeck coefficient. This work is devoted to the study of the reduction modes effect of hollow nickel oxide microspheres on the ratio of oxide and metal nickel forms in their structure. The paper presents the synthesis of microspheres by the pyrolysis of ultrasonic aerosols of an aqueous solution of nickel nitrate. Composition and morphology are studied by scanning electron microscopy and X-ray non-standard quantitative analysis. It was shown that the proportion of metallic nickel increases with an increase in the reduction temperature to about 375°C and then changes slightly. For microspheres, reduced at 350 °C, the main parameters of the thermoelectrochemical cell were determined. It was shown that the hypothetical Seebeck coefficient in the assembled cell system is 3.1 mV/K, and the resistance to charge transfer across the electrode-electrolyte interface was less than 1 Ohm. It confirms the applicability of these materials as electrodes for electrochemical systems and the possibility of obtaining high values of output power.

An important direction in the development of energy saving policy is harvesting and conversion into electricity of low-grade waste heat. The present paper is devoted to the improvement of the efficiency of thermo-electrochemical cells based on carbon fiber electrodes and potassium ferri-/ferrocyanide redox electrolyte. The influence of the carbon fiber electrode surface modification (magnetron deposition of silver and titanium or infiltration implantation of nanoscale titanium oxide) on the output power and parameters of the impedance equivalent scheme of a thermo-electrochemical cell has been studied. Two kinds of cell designs (a conventional electrochemical cell with a salt bridge and a coin cell-type body) were investigated. It was found that the nature of the surface modification of electrodes can change the internal resistance of the cell by three orders of magnitude. The dependence of the equivalent scheme parameters and output power density of the thermoelectric cell on the type of electrode materials was presented. It was observed that the maximum power for carbon fiber modified with titanium metal and titanium oxide was 25.2 mW/m2 and the efficiency was 1.37%.

The electrical properties of dispersions of a powdered ferroelectric nanocomposite based on ilmenite (FeTiO3) and hollandite (K1.46Ti7.2Fe0.8O16) in dioctyl phthalate have been studied by impedance spectroscopy techniques in a frequency range of 10–1–106 Hz. The influence of stabilizing additives of cationic and anionic surfactants and iron acetylacetonate on the permittivity, conductivity, and dielectric losses was determined for dispersions containing 40 mass % of the solid composite. The influence of composition on the mechanisms of relaxation processes in the system is discussed.

Owing to their exceptional mechanical, electrical and thermal properties, carbon nanotubes (CNTs) are ideal candidates for improving the performances of polymer composites. In the present work, we investigated the effect of CNT addition on the electrical conductivity of two types of carbon black (CB) filled polymer. Also, two different methods of compounding were applied and their effects are compared: mixing by a laboratory compounder Haake Rheomix Polylab and mixing by a twin-roller mixer. Composites containing a total of 10% by weight of different carbon fillers (CB, CNTs and their mixtures in a ratio of 8/2) were thus obtained, characterized by scanning electron microscopy and their frequency dependence of the electrical conductivity was measured. It is shown that the alternating current (AC) conductivities display two regions: a low frequency region of constant conductivity and a higher frequency region of increasing conductivity with increasing frequency (following the percolation scaling law). It was also observed that the samples compounded with twin-roller mixer exhibit a higher electrical conductivity than those obtained with the laboratory compounder. Moreover, the conductivity of the composites containing CNTs in addition to CB is found to be higher than the conductivity of the composites containing only CB.

We have studied the crystallization of potassium polytitanates (PPTs) modified in aqueous solutions of salts of various transition metals. The results demonstrate that the modified materials crystallize in the form of solid solutions with the hollandite structure. Ceramic materials obtained using the PPT/Fe, PPT/Ni, and PPT/Co systems have high dielectric permittivity in the low-frequency region (e ~ 105), whereas PPT/Cu ceramics have lower e (~103), retaining it to a frequency of 1 MHz, and very low dielectric losses (tanδ ~ 10–2).

The main parameter, that determines the use of thermoelectrochemical converters (TECC) for the waste heat harvesting is the efficiency of thermoelectric conversion. An increase of the current density at the electrode is possible due to the use of heterogeneous redox catalysts. In this paper, early results of Ti-based mineral catalysts usage are presented. A new type of thermoelectrochemical cell for in situ FTIR spectroscopy was designed, assembled and tested. With its use, the pattern of the redox reaction in K 3 [ F e ( C N ) 6 ] ↔ K 4 [ F e ( C N ) 6 ] conversion was confirmed.

Low-grade waste heat harvesting and conversion into electric energy is an important way of renewable energy development and thermo-electrochemical cells are promising devices to solve this problem. In this paper, we report original data on the current density and maximum output power dependents on voltage of the thermos-cells with nickel hollow microspheres electrodes and different electrolyte concentration (from 0.1 to 3.0 mol/l)which exhibit excellent hypothetical Seebeck coefficient and accordingly high open-circuit voltage values at low source temperature. The composition, microstructure and morphology of the hollow nickel microspheres based electrodes are included here. Because of the low cost of nickel based thermo-cells could be commercially feasible for harvesting low-quality thermal energy, in this connection, the raw data of measurements of their properties are given here. The data is related to "High Seebeck coefficient thermo-electrochemical cell using nickel hollow microspheres electrodes", Burmistrov et al., Renewable Energy, 2020 [1].

The present paper discusses the possibility of simultaneously using two methods for the modification of multi-walled carbon nanotubes - high-temperature annealing and halogen-assisted modification. The nanotube modification was carried out during the high-temperature annealing in the presence of iodine. A change in the structure and an increase in the electrical conductivity of the modified multi-walled carbon nanotubes was observed.

While conversion of low-grade waste heat into electricity is an important energy harvesting strategy, the thermo-electrochemical cells are one of the most promising devices for this application. This paper shows the study on thermo-electrochemical cell with polymer electrodes coated by oxidized multi-walled carbon nanotubes and the Fe(CN)6 3-/Fe(CN)6 4- based electrolyte. The developed cell demonstrates the current density values of more than 13 A/m2 and a specific power of 140 mW/m2. Hypothetical Seebeck coefficient was found equal to 0.7 mV/K by the calculation based on the temperature dependencies of the open circuit voltage.

This paper is about the investigation of the possibility of using polymeric and mineral hydrogels based on acrylic acid and liquid glass, modified by potassium titanate as thermoelectric elements, with the operation principle based on electrochemical processes at the solid electrolyte-electrode interface. Electrophysical characteristics of thermoelectrochemical cells were measured. The dependences of the open-circuit potential difference on the temperature gradient for cells based on zinc electrodes and various types of hydrogels are established. Hypothetical coefficient of Seebeck, calculated from the experimental data, was 1.5 mV/K for cells with electrolyte based on polyacrylic acid and 5.4 mV/K for cells with a mineral hydrogel. Thermogravimetric analysis of investigated electrolytes was shown that operation temperatures for polyacrylic electrolyte is lower of 80 °C, and for mineral hydrogel lower of 100 °C.

The effect of the firing temperature on the phase composition and electrophysical properties of ceramic articles obtained on the basis of compacted powders of the product of the interaction of potassium polytitanate and water solutions of iron (III) salts is investigated. When fired at temperature near 700°C (optimal value) the ceramic has pronounced properties of a solid electrolyte and is formed on the basis of a solid solution with the composition K1.46Ti7.2Fe0.8O16. At higher temperatures this solid solution becomes unstable and partially decomposes.

Potassium polytitanates are new promising type of ferroelectric ceramic materials with high ionic conductivity, highly polarizable structure and extremely high permittivity. Its structure is formed by [TiO6] octahedral units to layers with mobile potassium and hydroxonium ions in-between. The treatment in solutions containing nickel ions allows forming heterostructured materials which consist of potassium polytitanate particles intercalated by Ni2+ ions and/or decorated by nickel oxides NiOx. This modification route is fully dependant on solution pH, i.e. in acidic solutions the intercalation process prevails, in alkaline solutions potassium polytitanate is mostly decorated by the oxides. Therefore, electronic structure and electrical properties can be regulated depending on modification conditions, pH and ions concentration. Here we report the data on electric properties of potassium titanate modified in nickel sulfate solutions at different pH.