Natalja Lomanova

• Researcher at Ioffe Institute

Представлены результаты анализа температурного поведения намагниченности для соединений Bim+1Fem-3Ti3O3m+3 (m = 4, 5.5, 7, 8, 9). Измерения проводились в интервале температур 4.2–300 K. Показано, что для фаз с m = 4 и m 4 соответственно простая и модифицированная логистические модели Хилла точно совпадают с экспериментальным температурным поведение...

Bismuth ferrites have attracted much attention in recent years because of the possibility of their promising practical applications in sensing systems as well as digital memory. In this study, nanocrystalline material based on bismuth ferrite with mullite-like structure was synthesized by solution combustion technique. The results of XRD confirmed...

Nanocrystalline magnetically ordered materials based on bismuth and yttrium orthoferrites have been synthesized by the solution combustion method. The obtained materials demonstrate a significant difference between their magnetic properties and the properties of pure orthoferrites, in particular, a significant increase in the magnetic response.

The functional characteristics of materials based on bismuth titanate Bi2Ti4O11 largely depend on the synthesis conditions. The preparation of nanocrystals of this compound is topical in connection with the problem of miniaturization of electronic components. The features of phase formation and the optimal conditions for the formation of a nanocera...

Layered perovskite-like oxides with the Aurivillius phase’s structure are promising for high-technology industries such as magnetoelectronics, photonics, and catalysis. This work reports the synthesis condition and magnetic properties of the Sr-doped ceramic materials (BSFTO) based on four-layer Aurivillius phase Bi5FeTi3O15. (Bi1−xSrx)5FeTi3O15−δ...

The spatial spin modulated structure (SSMS) of the cycloid type present in bulk BiFeO3 prevents the linear magnetoelectric effect. One way to influence this structure is to reduce the crystal size to the nanoscale. Various opinions are circulating in the literature about the effect of nanocrystal size on SSMS, and to investigate this issue, we used...

В работе определены магнитные характеристики нанокомпозитов на основе ферритов висмута со структурой перовскита и муллита.

Materials with a layered perovskite-like structure of the Aurivillius phase type are important for such fields of technology as magnetoelectronics and photocatalysis. The paper describes the features of phase formation during the synthesis of nano- and macrocrystalline materials based on the Bi 6 Fe2Ti 3 O 18/ 8 compound with the five-layer Aurivil...

The features of the synthesis, structure, and properties of layered perovskite-like compounds of the Aurivillius family in the Bi4Ti3O12–BiFeO3 system are considered. Among the issues discussed, the main attention is paid to the analysis of relationships among the distribution of cations in the structure, on the one hand, and the formation mechanis...

This paper analysis the temperature dependence of FC and ZFC magnetization for Bi5FeTi3O15 multiferroic. It has Aurivillius four-layer phase structure. The analysis evidence on the influence of the grains of this material on its overall magnetic properties. The lack of a dramatic temperature threshold in the FC(ZFC) dependences may result in spin c...

The magnetic characteristics of a nanocrystalline material based on bismuth ferrite Bi2Fe4O9 with 60±3 nm crystallites were studied. The obtained material demonstrates unusual magnetic properties, which are manifested in a significant increase in the value of magnetization in comparison with the data known from other works.

This paper analysis the temperature dependence of FC and ZFC magnetizationfor Bi 5 FeTi 3 O 15 multiferroic. It has Aurivillius four-layer phase structure. The analysis evidence on the influence of the grains of thismaterial on its overall magnetic properties. The lack of a dramatictemperature threshold in the FC(ZFC) dependences may result in spin...

The magnetic characteristics of a nanocrystalline material based on bismuth ferrite Bi 2 Fe 4 O 9 with 60±3 nm crystallites were studied. The obtained material demonstrates unusual magnetic properties, which are manifested in a significant increase in the value of magnetization in comparison with the data known from other works. Keywords: nanocryst...

The process of formation by the chemical coprecipitation method of nanoceramic material based on layered perovskite-like complex oxide Bi 13 Fe 5 Ti 6 O 39 with the structure of the Aurivillius phase has been described. The temperatures of the onset of formation, the onset of decomposition, and activation of sintering, as well as the coefficient of...

The process of formation of nanoceramic material based on layered perovskite-like complex oxide Bi13Fe5Ti6O39 with the structure of the Aurivillius phase by the chemical coprecipitation method is described. The temperatures of the onset of formation, the onset of decomposition, and activation of sintering, as well as the linear thermal extension co...

In recent years, BFTOs Aurivillius phases pay attention due to their potential as single-phase nanostructured magnetic materials. Multilayered perovskite-like compounds with the highest level of multiferroic BiFeO3 in their structure have the most promising potential. This work reports the solid-state synthesis features, thermal behavior, dielectri...

The peculiarities presented of the magnetization for BiFeO3 nanoclusters with approximately 50 nm in size. They synthesized under conditions of solution combustion. When synthesized, the magnetic response of nanoclusters differs drastically depending on the type of fuel. If for the case of tartaric acid, the magnetic behaviour of the material follo...

BiFeO3 with 50–70 nm crystallites was obtained by glycine–nitrate combustion under varying conditions. These nanopowders demonstrated magnetic ordering at temperatures up to 400 K. The results were compared with the data known from other works, and it was shown that at the sizes lower than 70 nm the predominant contribution to the magnetization bel...

Изучены процессы намагничивания нанокомпозита BiFeO3−Bi2Fe4O9, полученного методом глицин-нитратного горения. Показано, что магнитные характеристики индивидуальных соединений BiFeO3 и Bi2Fe4O9 и композита существенно различаются. Новые свойства синтезированного вещества связываются с наличием обменного взаимодействия на границах раздела между фазам...

A single-phase material based on the complex oxide Ca2Fe2O5 doped with bismuth was synthesized by glycine-nitrate combustion. Characterization by x-ray diffractometry, helium pycnometry, scanning electron microscope, and elemental analysis showed that the material was isostructural to brownmillerite. The optimum temperature for the synthesis of the...

The formation of ceramics based on Bi1–xSrxFeO3–δ solid solutions produced by glycine-nitrate combustion was studied. The yield of target product was greatest for x = 0 – 0.5. The synthesis temperature range and start of grain sintering correlated with fusion of the surface phase. The sintering activation temperatures and thermal-expansion coeffici...

The magnetization processes of the BiFeO3 - Bi2Fe4O9 nanocomposite obtained by glycine nitrate combustion were studied. It was shown that the magnetic characteristics of the pure BiFeO3 and Bi2Fe4O9 compounds and the composite are significantly different. New properties of the synthesized substance are associated with the presence of exchange inter...

Глицин-нитратным горением синтезированы нанокристаллические магнитоупорядоченные материалы на основе ортоферрита висмута, допированного кальцием. Характеризация образцов методами рентгеновской дифрактометрии, гелиевой пикнометрии, методом BET, сканирующей электронной микроскопии и элемент-ного энергодисперсионного микроанализа, показала, что они из...

Nanocrystalline bismuth titanates Bi2Ti4O11 (115±5 nm), Bi4Ti3O12 (60±5 nm), Bi2Ti2O7 (105±5 nm), Bi8TiO14 (82±5 nm), and Bi12TiO20 (102±5 nm) were synthesized by heat treatment of the coprecipitated composition. It was revealed that the crystallite sizes of the target materials are determined by the minimum crystallite size of the first phase to c...

The features of the formation of nanocrystals in the BiFeO3–CaFeO3 system via glycine-nitrate combustion were studied. The crystallite size of the bismuth orthoferrite-based solid solutions (20–45 nm), as well as their particle size, were found to depend on the calcium content. The formation processes were activated in the temperature range corresp...

The minimum crystallite size in a group of oxides has been analyzed as a function of their synthesis conditions, critical nucleus size and the crystal structure parameters. Nanocrystals were synthesized by solution combustion, hydrothermal synthesis and heat treatment in air of the precipitated hy-droxides. Aluminum and iron oxides, titania and zir...

Nanocrystalline magnetically ordered materials based on Ca-doped bismuth orthoferrite were synthesized by glycine-nitrate combustion method. The samples were characterized by X-ray diffractometry, helium pycnometry, Brunauer–Emmett–Teller method, scanning electron microscopy and elemental energy dispersive microanalysis. It was shown that all sampl...

Formation of nanocrystalline bismuth titanate Bi2Ti2O7 with pyrochlore structure obtained via thermal decomposition of a co-precipitated product has been studied. The onset of vigorous formation of Bi2Ti2O7 has been shown to correlate with the melting point of the surface phase based on bismuth oxide. The upper temperature limit of the region of na...

The influence of synthesis conditions on the development, thermal behavior, and sintering characteristics was investigated for nano- and macro-crystalline Bi5FeTi3O15-based ceramic materials with a perovskite-like four-layered Aurivillius phase structure. It was shown that the start of grains sintering corresponds with the start of surface phase me...

The synthesis conditions' influence on the development, thermal behavior, and sintering characteristics was investigated for the nanoand macro-crystalline Bi5FeTi3O15 ceramic materials which had the structure of the perovskite-like four-layered Aurivillius phase. It was shown that the beginning of grains sintering is consistent with the beginning o...

The temperature behavior of bismuth orthoferrite nanoparticles obtained by the glycine-nitrate combustion method was studied by high-temperature X-ray diffractometry and complex thermal analysis. The region of stability of the material in a single-phase state was found. It was shown that the nanocrystalline BiFeO3 did not undergo decay in the tempe...

Mechanism by which nanocrystalline Bi4Ti3O12 is formed in thermal treatment of coprecipitated hydroxides was studied. It was shown that the onset of the active formation is correlated with the melting point of the surface phase based on bismuth oxide. The technological synthesis parameters of Bi4Ti3O12, at which crystallite sizes in the range 35–60...

The mixed-layer perovskite-like compound Bi13Fe5Ti6O39 with Aurivillius phase structure Bim+1Fem−3Ti3O3m+3 (m = 5.5) was synthesized by the solid-state reactions method. The thermal behavior of Bi13Fe5Ti6O39 in the range from 2 to 1450 K was studied by the differential scanning calorimetry, the impedance spectroscopy and the analysis of temperature...

Solid-state chemical reactions in the Bi2O3–SrO–TiO2–Fe2O3 system have afforded layered perovskitetype oxides with the Aurivillius phases structure: (Bi1–х,Srх)m–1Bi2Fem–3Ti3O3m+3–δ (m = 4–7). Special features of their formation and thermal behavior have been studied.

The magnetic properties of the Aurivillius phases Bim+1Fem−3Ti3O3m+3 with the number of layers in the perovskite-like block m = 5.5, 7, 8 were studied. These phases were found to possess magnetically ordered states at temperatures ranging from 175 to 255 K. Magnetic order of a weak ferromagnetic type was shown to exist in the alternating-layer phas...

Nanocrystalline bismuth orthoferrite has been synthesized under conditions of glycine-nitrate combustion. Temperatures of activation of formation and growth of BiFeO3 nanocrystals have been shown to correlate with melting temperature of surface (non-autonomous) phases. Optimal temperature of synthesis of nanocrystalline bismuth orthoferrite has bee...

Distinctive features of dielectric properties of a ceramic material based on Aurivillius phase Bi 10 Fe 6 Ti 3 O 30 have been studied.

Formation of nanocrystals in the Bi2O3-Fe2O3 system prepared by the co-precipitation of bismuth and iron hydroxides has been studied. The temperature of onset of the BiFeO3 and Bi2Fe4O9 nanocrystals formation is correlated with the melting point of the non-autonomous phases. The optimal temperature of BiFeO3 and Bi2Fe4O9 nanoparticles synthesis is...

The mechanism of BiFeO3 nanoparticle formation from initial compositions obtained by bismuth and iron hy-droxides co-precipitation has been studied. The activation temperature of the BiFeO 3 nucleation and nanocrystal growth is shown to correlate with that of the nonautonomous phase's melting. The optimal temperature range during nanoparticle forma...

The Aurivillius phases Bin+1Fen−3Ti3O3n+3 have been synthesized via solid state reactions. Mössbauer spectroscopy and X-ray analysis have revealed the dependence of Fe ions distribution over the nonequivalent sites and of unit cell parameters on the number of perovskite-like layers in the Aurivillius phases. Said dependencies are shown to undergo a...

The electrical properties of layered perovskite-like compounds with the general formula Bim + 1Fem − 3Ti3O3m + 3 have been studied in relation to their physicochemical properties and structure.

Specific features of the thermal behavior of Bim + 1Fem−3Ti3O3m + 3 layered perovskite-like compounds (where m takes integer and some fractional values between 3 and 9) were considered, and the temperature limits of stability of these compounds were determined. The phase diagram of the Bi4Ti3O12-BiFeO3 section through the Bi2O3-TiO2-Fe2O3 system wa...

The effect of the phase composition of the starting mixture on the formation of the layered perovskite-like compound Bi7Fe3Ti3O21 in the Bi2O3-TiO2-Fe2O3 system is reported. The rate-limiting process in the formation of this compound is reactant mass transfer to the reaction zone.

The thermal properties of compounds of the general formula Bi m + 1 Fe m − 3 Ti3O3m + 3, which are layered perovskite-like phases of the Aurivillius type, are investigated as a function of their composition. It is demonstrated that the temperature of decomposition of the Bi m + 1 Fe m − 3 Ti3O3m + 3 compounds decreases with an increase in the thick...

Phase transformations in the oxide binary section of the UO2-FeO-Fe ternary system were studied. The melting onset point of the UO2-FeO heterogeneous system (13355C) was determined and the fusion curve of this system was constructed. The limiting solubility of FeO in the UO2 solid solution was measured. The changes in crystal parameters in formatio...

A number of new Bi m+1Fe m-3Ti 3O 3m+3 compounds with integer and fractional m values are identified in the Bi 4Ti 3O 12-BiFeO 3 system. All of the compounds are shown to have Aurivillius-type structures. The phase-transition and decomposition temperatures of the new and earlier known compounds of the Bi 4Ti 3O 12-BiFeO 3 system are determined. The...

The SiO2-Fe2O3(F3O4) system has been studied in air, oxygen, and an inert atmosphere. The dissociation temperatures for iron oxides, the onset and full melting temperatures for coexisting phases, and the melt demixing temperatures have been determined as a function of the oxygen partial pressure. A scenario of the phase and chemical transformations...

Active formation of BiFeO3 was observed at temperatures exceeding the temperature limit of its stability. The process mechanism was elucidated.