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Original papers Nanostructured, nanoscale materials and nanodevices
УДК 546.824;665.7.035.8 DOI: 10.17277/jamt.2022.01.pp.068-077
Synthesis and dielectric properties of K^Fe^Ti^O^ ceramics produced by the Pechini method
Alexey R. Tsyganova Alexander V. Gorokhovskya, Maria A. Vikulovaa, Denis I. Artyukhova, Dmitry A. Zakharievichb, Svetlana I. Sauninab, Nikolay V. Gorshkova
a Yuri Gagarin State Technical University of Saratov, 77, Polytechnicheskaya St., Saratov 410054, Russian Federation, b Chelyabinsk State University, 129, Br. Kashirinykh St., Chelyabinsk 454001, Russian Federation
Abstract: Potassium titanate modified with Fe3+ ions matching the stoichiometry of K16Fe16Ti6.4O16 (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 singlephase 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 А и c = 2.9659 A. 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.
Keywords: hollandite structure; Pechini method; ceramic; impedance; dielectric properties; permittivity; dielectric losses; nanopowder.
For citation: Tsyganov AR, Gorokhovsky AV, Vikulova MA, Artyukhov DI, Zakharievich DA, Saunina SI, Gorshkov NV. Synthesis and dielectric properties of KL6Fei.6Ti6.4Oi6 ceramics produced by the Pechini method. Journal of Advanced Materials and Technologies. 2022;7(1):68-77. DOI: 10.17277/jamt.2022.01.pp.068-077
Синтез и диэлектрические свойства K1.6Fe1.6Ti6.4Oi6 керамики, полученной методом Печини
А. Р. Цыганова А. В. Гороховскийа, М. А. Викуловаа, Д. И. Артюхова, Д. А. Захарьевичь, С. И. Саунинаь, Н. В. Горшкова
а Саратовский государственный технический университет имени Гагарина Ю. А., ул. Политехническая, 77, Саратов 410054, Российская Федерация, ь Челябинский государственный университет, ул. Братьев Кашириных, 129, Челябинск 454001, Российская Федерация
Аннотация: Титанат калия, модифицированный ионами Бе3+ и соответствующий стехиометрии Kj.5Fe1.6Tig.4Oi6 (КЕТО), получен методом полимерных комплексов прекурсоров (метод Печини). Фазовый состав, распределение частиц по размеру и морфология образцов полученных материалов были охарактеризованы методами рентгенофазового анализа (РФА), дифракции лазерного излучения и СЭМ. Рентгенофазовый анализ показывает однофазное образование титаната калия с тетрагональной структурой голландита. Для уточнения параметров кристаллической решетки использован метод Ритвельда. Параметры решетки составляют: а = Ь = 10,151 А и с = 2,9659 А. Результаты СЭМ и дифракции лазерного излучения показали, что частицы исследуемого нанопорошка имеют кубическую форму и средний размер 400 нм. Диэлектрические свойства в диапазоне частот 0,1 Гц до 1,0 МГц исследованы для керамических дисков, полученных методом спекания, спрессованного
нанопорошка при 1080 °C. Установлено, что керамика на основе твердых растворов KFTO обладает высокой диэлектрической проницаемостью и низкими диэлектрическими потерями и характеризуется повышенной поляризуемостью структуры. Высокая поляризуемость материала объясняется относительно высокой подвижностью ионов K+ в туннеле рассматриваемой структуры голландита, сопровождающейся перераспределением электронов в кристаллической решетке. Приведено обсуждение вклада различных процессов в диэлектрическую проницаемость.
Ключевые слова: структура голландита; метод Печини; керамика; импеданс; диэлектрические свойства; диэлектрическая проницаемость; диэлектрические потери; нанопорошок.
Для цитирования: Tsyganov AR, Gorokhovsky AV, Vikulova MA, Artyukhov DI, Zakharievich DA, Saunina SI, Gorshkov NV. Synthesis and dielectric properties of K1.6Fe1.6Ti6.4O16 ceramics produced by the Pechini method. Journal of Advanced Materials and Technologies. 2022;7(1):68-77. DOI: 10.17277/jamt.2022.01.pp.068-077
1. Introduction
As a result of accelerated development of electronics, the materials with high dielectric permittivity and low dielectric losses and high structural stability are increasingly in demand. Among these materials, ceramic materials with perovskite structure have become a popular research topic due to their satisfactory dielectric properties and versatility [1]. In recent decades, BaTiO3 has become the most successfully commercialized dielectric material for electronic devices such as capacitors, converters and sensors due to its excellent dielectric, ferroelectric and piezoelectric properties [2-5]. Special mention should be paid to miniature multilayer ceramic capacitors (MLCC) [6]. With their good frequency response, higher reliability, high breakdown voltage, superior volumetric capacitance efficiency and reduced cost, MLCC with BaTiO3 ferroelectric compositions are already competing with conventional high-capacity Al- or Ta-electrolytic capacitors. In applications such as mobile electronic equipment (cell phones or laptops), these MLCC types dominate at present and will also play an important role in the future [7]. This one is related to their excellent dielectric properties such as high polarization, high dielectric constant (s = 3600 at 25 °C and at 100 kHz) and relatively low dielectric losses (tan S = 0.032). In addition to barium titanate, last decade, ceramics of the composition CaCu3Ti4Oi2, characterized with a colossal dielectric constant (CDC), are of great interest too [8-10]. However, CCTO ceramics have high tan(S) values that limit its practical application. In this regard, the development and study of various oxide systems with high permittivity is an urgent task [11].
Complex oxides Kx(Me,Ti)8O16 with hollandite structure [12, 13] can be considered as new materials with high permittivity. Hollandite family can be represented by the general formula AxB8O16, where A are tunnel cations, B are octahedral cations. The elementary cell AxB8O16 can have different
occupancy of tunnel cations (0 < x < 2). The cations are usually represented by groups of univalent alkali and divalent alkaline earth metals, such as Li , Ba , etc.; and B cations can be represented by different metals or transition elements with different sizes and oxidation degrees, such as Ti , Ti , Mg , Fe, Ni, Al , Fe , Sn4+ etc. Depending on the average sizes of A and B cations, hollandite can have tetragonal (I4/m) or monoclinic (I2/m) symmetry with tunnels along the crystallographic c or b axis, respectively [14-16]. Hollandite-like materials are outstanding representatives of tunnel oxides with a wide range of applications, including anode materials for solid-state batteries [17], carrier grids for radionuclide removal [18], etc. In the last decade, it has been noted that a group of oxide materials characterized by a tunnel structure similar to hollandite has been characterized by enormous permittivity [19, 20]. As shown in [19], the K1.53Cu0.76Ti7.24O16 copper-doped hollandite-like potassium titanate was obtained by treating the amorphous potassium polytitanate with aqueous solutions of copper sulfate followed by calcination at 900 °C. These materials were found to have a high permittivity (s = 2000, S = 0.6 at 25 °C, at 1 kHz). In addition it is shown [21] that hollandite-like solid solutions are promising ceramic fillers for polymermatrix composites due to their stable and high value of permittivity. It is important to note that the replacement of some Ti4+ positions by divalent or trivalent transition metals, which promotes the formation of hollandite-like solid solutions Kx(Me,Ti)8O16, contributes to an increase in polarization ability and permittivity [20]. Although the crystal structure of the hollandite-like materials has been studied in detail, no systematic approach has yet been undertaken to study the dielectric properties of this material class.
The main methods to produce the hollandite-like ceramics are: solid-state reactions [19-22], sol-gel method [23-26] and hydrothermal synthesis [27]. The disadvantages of these methods include: high
synthesis temperature, long reaction time, low control of stoichiometric composition, and large particle sizes. For this reason, exploring new ways to synthesize this material is very important to guaranty the required stoichiometry, minimum content of secondary phases and particle size, as well as controlled morphology, necessary to improve material properties for its applications. For such systems, the Pechini method is applicable [28-30], where the synthesis takes place by forming a polymeric precursor in which the metal ions of interest are evenly distributed along the macromolecular chains produced by esterification and polymerization reactions between citric acid and ethylene glycol. The advantages of this method include a possibility to obtain nanopowders with high control of stoichiometry and purity, low synthesis temperatures and high reproducibility. In addition, the resulting powders do not require a use of the additional milling for further fabrication of ceramic products with low porosity.
The hollandite composition similar to K1.6Fe1.6Ti6.4Oi6 was previously obtained in works [12, 24], but so far there have been no studies of ceramic dielectric properties in this class of materials. In addition, iron ions have a variable valence, which can lead to an increase in polarization of the dielectric and increase its permittivity. In this connection, a study of iron-containing material with a hollandite structure is of scientific and practical interest. As part of this study, a modified sol-gel method with the addition of ethylene glycol was successfully tested, which promotes the polymerization of chelates and reduces the ion mobility during the synthesis. The use of this synthesis method made it possible to obtain a pure structure of hollandite without impurity phases. This study for the first time contains the results of a study of the dielectric properties of K1.6Fe1.6Ti6.4Oi6 in a wide frequency range, a detailed description of impedance spectroscopy data indicating the processes occurring in the grain and at the grain boundary, an equivalent scheme is proposed and the corresponding parameters were calculated.
Thus, the aim of this paper was to obtain a solid solution with the general formula of K1.6Fe1.6Ti6.4O16 (KFTO) by the Pechini method and study the dielectric properties of the ceramics based thereon.
2. Materials and methods 2.1. Synthesis of K^Fe^Ti^O^
Precursor materials used for the synthesis of nanopowders in the K2O-TiO2-Fe2O3 system were ethylene glycol (99 %, Russian Standard 10164-75),
citric acid (99.8 %, Russian Standard 3652-69), KNO3 (98 %, Russian Standard 4217-77), Fe(NO3)3x x 9H2O (98 %, TC 6-09-02-553-96), C16H36O4Ti (97 %, Aldrich), HNO3 (65 %, Russian Standard 4461-77), aqueous ammonia (25 %, Russian Standard 3760-79).
The methodology of nanopowders producing included several steps. Nitrates of the corresponding metal ions were dissolved in a minimal amount of distilled water, and then added to titanium butoxide in stoichiometric ratios corresponding to K1.6Fe1.6Ti6.4O16. An aqueous solution of nitric acid, citric acid, and ethylene glycol were added to the resulting mixture. Optimal stoichiometric ratios were determined experimentally in advance Ti : C6H8O7 = 1.5; Ti : C2H6O2 = 5.5; Ti : NO3 = 1.8. After titanium butoxide was completely dissolved, a 10 % NH4OH solution was added to the solution until pH = 8 was established. According to the Pechini method, the next step was made to evaporate the solvent and support polymer resin formation in a drying oven at 240 °C to initiate a self-sustaining combustion reaction and provide extraction of the released NO2. The gel first underwent melting, then boiling, and then swelled into black foam, which finally burst into flames and burned to black ash. The combustion continued for several minutes with a smoldering flame. The resulting amorphous ash was annealed at 900 °C in an electric furnace for 20 minutes to produce crystalline nanopowders.
2.2. Characterizations
To study the dielectric properties, the KFTO powder was pressed in a stainless steel mold at 150 MPa (disk diameter 12 mm, thickness 1 mm) and sintered at 1080 °C to form monolithic ceramic bodies. The obtained ceramic discs were coated with silver-palladium adhesive (Trademark K13, Russia).
The phase composition of the ceramic material was studied using the X-ray diffractometer Thermo Scientific ARL X'TRA (Cu Ka radiation, I = = 0.15412 nm). The morphology of the samples was analyzed using the scanning electron microscope Vega3 Tescan. The fractional composition of the obtained powders was studied using the laser particle size analyzer Analysette 22 MicroTecplus (Fritsch), recalculation of the experimental data was performed in the MaScontrol software using the Fraunhofer theory. Raman spectra were acquired from powder samples using a Bruker Raman microscope, scanning with a green laser of wavelength 514 nm in the range from 250 to 2000 cm 1. The measurement of the
electrical properties of the obtained ceramic disks were determined by impedance spectroscopy (Novocontrol Alpha AN impedance analyzer) in the frequency range from 0.1 Hz to 1.0 MHz at a voltage amplitude of 100 mV.
3. Results and discussion
Figure 1a shows the XRD patterns of the synthesized KFTO specimens. As can be seen, all the reflexes fully correspond to pure KFTO with a tetragonal hollandite-like structure (spatial group l4/m, JCPDS No. 77- 0990). It is worth noting the absence of impurity crystal structures, such as Fe2O3, FeTiO3, which confirms the replacement of titanium with iron injected during the synthesis. For the sample sintered at 1080 °C, the diffractogram shows a presence of the Fe2TiO5 reflexes. The formation of Fe2TiO5 crystals on the grain boundaries can be considered as a result of oxygen loss from the grain mass during high-temperature sintering and diffusion of iron from the bulk of the grains to their boundaries, as well as subsequent re-oxidation during cooling of sintered ceramics [31-33].
The structure of the synthesized hollandite-like ceramics is shown in Fig. 1b. The KFTO structure of the hollandite consists of interconnected (Fe,Ti)O6 octahedrons forming a framework with tunnels filled with K+ ions (the potassium ions displacement is shown by purple sectors in Fig. 1b). Titanium ions have a mixed valence +4 (dark colored atoms in the center of octahedrons) or +3 (light colored atoms in
the center of octahedrons) and can be replaced by ions of various transition metals, such as Fe3+ in this case.
Figure 1c shows a typical plot of the final Rietveld refinement, indicating a good match between the experimental and calculated intensities in the tetragonal system with spatial group I4/m. The factors of the final convergence agreement are satisfactory: Rp = 12.86 %, Rwp = 17.36 %. The calculated parameters of the lattice are a = b = 10.151 Á and c = 2.9659 Á, theoretical density (^theor) 3.86 g-cm . Calculated convergence factor GOF = 4.03. The cell constants are in fairly good agreement with comparable compositions of priderites, taking into account the ionic radii of the doping metals [12].
Figure 2 shows the particle size distribution and the SEM micrograph of the obtained ceramic powder. As can be seen, the particles are characterized by uncertain morphology and an average size of 400 nm.
Using literature data on Raman bands characteristic of titanates and experimental results (Fig. 3), we correlated the Raman bands of our samples with different types of vibrations of their constituent elements. The 375 cm 1 band, for a compound with a tunneling Hollandite-like structure of K.1.6Fe1.6Ti6.4O16 composition, probably corresponds to the strain vibrations of (Fe,Ti)O6 octahedrons. The 449 cm1 band corresponds to Ti-O vibrations in a one-dimensional channel of hollandite structure.
ceramic 1080 °C
powder 900 °C
*Kl.óFe1.6Tió.4°16 ♦ Ti02 (Rmile) V Fe2Ti05
* *
^«jJlüUy^ _i_,_i_._i_,_i_,_i_,_i_,_i_i_i_,_i_._i_,_i
10 15 20 25 3« 35 40 45 50 55 28, degree
(a)
60
s = lo.isloa b = 10.1510 A r » 2.9650 A cc= P = y = 90.00° Volume - 305.il A3 J - 3.86 iW
•■■r
Gar-4X3 k|1 = 12.s6 n Hp = 17.36
20, degree
(c)
Fig. 1. X-ray pattern (a) of the powder KFTO sample; (b) crystal structure of hollandite-type KFTO; (c) the refined Rietveld plot showing experimental (black ball), calculated (red line) and difference (blue line) for priderite powder KFTO
fñ o
300 400 590 600
x, ^.m
(a (b)
Fig. 2. SEM micrography and particle size distribution for nanopowders KFTO (x is particle size, ^m; dQ3(x) is differential percentage of particle volume entering the range between the minimum and maximum size; Q3(x) is integral percentage of the particle volume relevant to the range in question, showing which fraction of the particle volume is below the specified size)
of polar dielectric materials. This feature is independent of the composition and stoichiometry of such materials. The displayed trend can be understood using the Wagner's theory. As can be seen, the resulting ceramics has high permittivity in the region of low frequencies (s' = 2.3-104). In the range of medium frequencies (1 kHz) s' = 2.6-103, and at high frequencies s' decreases down to 7-10 . It should be noted that traditionally the dielectric permittivity consists of three main components: the dipole grain (electronically anchored defective dipole); the grain interface (internal layer capacitance barrier); and the effect of electrode polarization [31]. At high frequencies (f > 105 Hz), permittivity occurs only due to the grain effect; at medium frequencies (10 < f< 105), the
grain effect contribution is accompanied with a grain boundary effect corresponding to the IBLC model; while the electrode polarization effect occurs at low frequencies (f < 10). The high permittivity should be associated with the formation of either thin oxide films or secondary phases at the grain boundaries. In our study, Fe2TiO5 can be considere as a secondary phase. Thus, a structure represented by semiconducting grains and insulating grain boundaries characterized by increased polarizability and high value of s' can be formed. The high polarizability of the synthesized material may be explained by relatively high mobility of K+ ions in the tunnel of the considered hollandite-like structure, accompanied by the redistribution of electrons in the crystalline titanate lattice through the (Ti4+ ^ Ti3+ - e ) and (Fe3+ ^ Fe2+ - e ) processes. The electrical conductivity of the tested
%0 1000 1100 1200
Wavenumber (cm ) Fig. 3. Raman scattering spectra of priderite powder KFTO
These Ar-symmetry vibrations arising due to splitting of degenerate TiO6 octahedron modes refer to the Ramman bands at 449 and 270 cm-1 [34]. The 661 cm-1 band can determine the titanium oxygen vibrations and the 840 cm-1 band probably corresponds to the valence vibrations of (Fe,Ti)O6 octahedrons [35]. The 923 cm-1 band refers to the stretching vibrations of the Ti-O bonds including the unbound oxygen that K+ ion coordinates with.
The electrical properties of the KFTO-based ceramics were studied in the frequency range of 10-1-106 Hz at the room temperature. Figure 4 shows the frequency dependence of permittivity (s'), dielectric losses (tan S) and conductivity (a) for a ceramic disks sintered at 1080 °C. The permittivity values show a tendency to decrease with increasing frequency (Fig. 4a), which is a characteristic property
!0
10-4!
10" i
S
írt
O
10 "i
Ifl'l
10
1U1 JO"1 10* l(l' 10* l»J III" 10f III' 10'
f, H2
(b)
Fig. 4. Frequency dependence of the real part of complex permittivity (s') and dielectric losses (tan S) (a) conductivity (a) (b) for the obtained ceramics
specimens increases with frequency and has high values for the ceramic materials in the low frequency
9 -3 1
range of 1.5-10 , and 4.5-10 S-cm in the high frequency range. This one indicates a presence of the potential barrier, which can be related to the boundary among the grains [32, 33].
As shown in Fig. 5 impedance hodographs have a typical appearance with small arcs and large arcs corresponding to high-frequency and low-frequency regions, respectively. The parallel appearance of small and large arcs indicates that a heterogeneous structure is formed in the sintered ceramic. The equivalent electric scheme consists of the following elements (Fig. 5): R1, which describes the total resistance of contacts and wires, is not involved in the analysis. R2 of the crystallite volume and grain boundaries, and the cascade connected in parallel consisting of resistance (grain boundary resistance); and constant phase elements CPE1 has an index n1 with a value close to 1, which allows it to be interpreted as capacity. In this case the value of CPE1 10-9, which is comparable to the grain boundary capacitance [36] and CPE2 in turn has an index n2 close to 0.5, which is interpreted as the impedance diffusion element whose value is presented in Table 1. An impedance study showed that the charge transfer in the studied sample is limited by barriers at the grain boundary and diffusion of charge carriers, which describe processes of charge transfer along the grain boundaries [37]. The calculated parameters of the equivalent circuit are presented in Table 1.
Two semicircles and a straight line with a certain slope angle are apparent in the Cole-Cole diagram (Fig. 6) for the dielectric permittivity. This indicates
the presence of two relaxation processes as well as the contribution of the different components to the dielectric permittivity value, which can be determined using the adapted Gavriliak-Negami equation [38]:
100 n
100
z\ MQ
Fig. 5. The impedance spectroscopy (Nyquist plot) of KFTO-based ceramics measured at room temperature
Table 1. The values of the equivalent impedance circuit elements
Parameters Value
R1, Q 75.85
R2, Q 20 300 000
CPE1, nF 4.8
n1 0.851
CPE2, GQ-1 sn 9.14
n2 0.579
sn
25000 -
20000 -
15000 -
10000 -
5000-
s' 600
400
200
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
5000
10000
15000
20000
25000
Fig. 6. Illustration of Cole-Cole model for KFTO-based ceramics
*
s =
1 +(>T)
1-a
EPDD
1 +(>T)
1-a
J'a DC
(1)
IBLC
rasr
where s is the complex dielectric constant, is the permittivity at very high frequencies, s^ is the static permittivity (low frequency permittivity values), a = 2nf is the angular frequency, t is the mean
relaxation time, the exponent (1 - a) is a measure of the symmetric distribution of relaxation times, P is a measure of the asymmetrical distribution of relaxation times. The indices mean the contribution of dipolar grain (EPDD) and interfacial grain boundary (IBLC) to the permittivity value, respectively. Analysis of the Cole-Cole plot allowed us to determine the parameters of equation (1), which are summarized in Table 2.
Table 2. Eduation (1) parameters
Parameter EPDD IBLC
ss 2543.45 22432.64
s« 50 2626.39
a 0.597 0
ß 1 0.440
T, s 1.4710-9 0.908
Based on equation (1), Fig. 6 shows the multiple contributions of EPDD, IBLC and DC conductivity to the permittivity for KFTO ceramics. Based on this, the following assumptions can be made: the permittivity at high frequencies (106 Hz) consists only of the grain effect contribution (EPDD model); the dielectric constant at medium frequencies is determined by the contribution from grain and intergranular boundaries (IBLC), and in the low frequency region the contribution from crystal structure and microstructure as well as macro-interference between the metal electrode and heterogeneous ceramics is reflected. Calculated values of the elements of the equivalent impedance circuit for ceramic materials, confirm the presence of the above-mentioned processes. The equivalent circuit is represented by a two-series array of parallel RC (resistor and capacitor) elements. One of which contains the resistance R1 characteristic of semiconductor grains. The other (consisting of resistance R2 and CPE) represents the boundaries of insulating grains.
It is worth noting that the electrical properties of the hollandite synthesized in this study by the sol-gel method differ markedly from the properties of hollandite-like materials doped with other metals [19, 20]. The frequency dependence of conductivity is almost linear, with low values of odc in the low-frequency area. Based on this one, it can be assumed that the changing the grain size and/or the doping the hollandite structure with other transition metal ions and will allow to adjust the electrical properties of the ceramic products. In addition, according to the literature data, KFTO ceramics has values of
Ss s«
s« +
Es - S«
+
s« +
permittivity and dielectric losses similar to these ones for the perovskite-like dielectrics. That makes it possible to propose to use this material with a hollandite-like structure in the producing of ceramic capacitors and other electronic components.
4. Conclusions
In this paper, we studied powder material with hollandite-like structure and composition K1.6Fe1.6Ti6.4Oi6 obtained by the Pechini method, successfully optimized for obtaining a single-phase solid solution in the system K2O-Fe2O3-TiO2 during heat treatment at 900 °C for 20 minutes, as well as ceramics based on it after compacting and sintering at 1080 °C. The XRD analysis showed the formation of the tetragonal hollandite phase with the spatial symmetry group l4/m. Apart from the hollandite phase, no other impurity phases were detected, which confirms the high degree of control of stoichiometry and purity using the Pechini method. To determine the structural characteristics of the obtained solid solution representing interconnected (Fe,Ti)O6 octahedrons forming a frame structure with the tunnels filled with K+ ions, the Rietveld method was applied, according to which the calculated parameters of the tetragonal crystal lattice were a = b = 10.151 A and c = 2.9659 A. The use of SEM and laser diffraction methods made it possible to analyze the size and morphology of the particles obtained by the Pechini method. It was found that the powder structure is formed by particles with uncertain morphology and an average size of 400 nm. It was found that powder with the hollandite structure during sintering melts incongruently with the formation of TiO2 and Fe2TiO5 phases at the grain boundary. The dielectric properties of the K1.6Fe1.6Ti6.4O16 based ceramics measured by impedance spectroscopy allowed analyzing the frequency dependence of the real part of permittivity, dielectric losses and conductivity. The studied ceramics are characterized by high permittivity (especially in low-frequency region). In the middle frequency range (1 kHz) permittivity s' and dielectric losses (tan S) values are
respectively. The obtained results enable to recommend using the hollandite-like ceramic materials in manufacturing of various ceramic elements of electronic devices, as well as fillers for polymer matrices due to their huge permittivity and specific frequency dependence of the electrical properties.
5. Funding
The research was funded by the Russian Scientific Foundation (contract No. 19-73-10133).
6. Conflict of interests
The authors declare no conflict of interest.
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Информация об авторах / Information about the authors
Алексей Русланович Цыганов, младший научный сотрудник, ФГБОУ ВО «Саратовский государственный технический университет имени Гагарина Ю.А.» (СГТУ имени Гагарина Ю.А.), Саратов, Российская Федерация; ORCID 0000-0002-5112-7939; e-mail: [email protected]
Александр Владиленович Гороховский, доктор химических наук, профессор, заведующий кафедрой «Химия и химическая технология материалов», СГТУ имени Гагарина Ю.А., Саратов, Российская Федерация; ORCID 0000-0002-4210-3169; e-mail: [email protected]
Мария Александровна Викулова, кандидат химических наук, доцент, старший научный сотрудник, СГТУ имени Гагарина Ю.А., Саратов, Российская Федерация; ORCID 0000-0003-0092-6922; e-mail: [email protected]
Денис Иванович Артюхов, аспирант СГТУ имени Гагарина Ю.А., Саратов, Российская Федерация; ORCID 0000-0001-9753-8875; e-mail: mr.tokve@ gmail.com
Дмитрий Альбертович Захарьевич, кандидат физико-математических наук, доцент, ФГБОУ ВО «Челябинский государственный университет», Челябинск, Российская Федерация; ORCID 00000003-1184-9571; e-mail: [email protected] Светлана Ивановна Саунина, кандидат физико-математических наук, доцент, ФГБОУ ВО «Челябинский государственный университет», Челябинск, Российская Федерация; ORCID 0000-0003-12747032; e-mail: [email protected] Николай Вячеславович Горшков, кандидат технических наук, доцент, старший научный сотрудник, СГТУ имени Гагарина Ю.А., Саратов, Российская Федерация; ORCID 0000-0003-3248-3257; e-mail: [email protected]
Alexey R. Tsyganov, Junior Researcher, Yuri Gagarin State Technical University of Saratov (SSTU), Saratov, Russian Federation; ORCID 0000-0002-5112-7939; e-mail: [email protected]
Alexander V. Gorokhovsky, D. Sc. (Chemistry), Professor, Head of the Department «Chemistry and Chemical Technology of Materials», SSTU, Saratov, Russian Federation; ORCID 0000-0002-4210-3169; e-mail: [email protected]
Maria A. Vikulova, Cand. Sc. (Chemistry), Associate Professor, Senior Researcher, SSTU, Saratov, Russian Federation; ORCID 0000-0003-0092-6922; e-mail: vikulovama@yandex. ru
Denis I. Artyukhov, Postgraduate, SSTU, Saratov, Russian Federation; ORCID 0000-0001-9753-8875; e-mail: [email protected]
Dmitry A. Zakharievich, Cand. Sc. (Physics and Mathematics), Associate Professor, Chelyabinsk State University, Chelyabinsk, Russian Federation; ORCID 0000-0003-1184-9571; e-mail: [email protected]
Svetlana I. Saunina, Cand. Sc. (Physics and Mathematics), Associate Professor, Chelyabinsk State University, Chelyabinsk, Russian Federation; ORCID 0000-0003-1274-7032; e-mail: [email protected]
Nikolay V. Gorshkov, Cand. Sc. (Engineering), Associate Professor, Senior Researcher, SSTU, Saratov, Russian Federation; ORCID 0000-0003-3248-3257; e-mail: [email protected]
Received 24 December 2021; Accepted 18 February 2022; Published 14 April 2022
© Ф
Copyright: © Tsyganov AR, Gorokhovsky AV, Vikulova MA, Artyukhov DI, Zakharievich DA, Saunina SI, Gorshkov NV, 2022. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.Org/licenses/by/4.0/).
