Processes Occurring at Preparation of Ca3Co4O9+ Ceramics by Means of Different Solution Methods, and Its Properties

By means of complex independent methods the processes occurring at preparation of Ca3Co4O9+ ceram-ics using solid-state reactions and different solution (citrate, polymeric and sol-gel) methods were investi-gated. The crystal structure and microstructure, oxygen stoichiometry, thermal expansion, electrical con-ductivity and thermo-EMF of the samples were studied and values of their power factor were calculated. It is shown that usage of solution methods let us obtain more dense and fine-grained ceramics, which is char-acterized with higher values of electrical conductivity and power factor. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3525

Crystal structure, thermal and electrotransport properties of NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) solid solutions

Using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. It was found that NdBa1–xSrxFeCo0.5Cu0.5O5+δ phases crystallize in tetragonal syngony (space group P4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. Partial substitution of barium by strontium in NdBaFeCo0.5Cu0.5O5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values

Spin–state transition in the layered barium cobaltite derivatives and their thermoelectric properties

Ba1.9Me0.1Co9O14 (Me = Ba, Sr, Ca) (BCO) layered cobaltites were prepared by means of solid-state reactions method. Crystal structure, microstructure, thermal expansion, electrical conductivity, and thermo-EMF for the obtained oxides were studied; the values of their linear thermal expansion coefficient, activation energy of electrical transport, and power factor values were calculated. It was found that BCO are p-type semiconductors, in which the spin-state transition occurs within 460-700 K temperature interval due to change in spin state of cobalt ions, which accompanied the sharp increase in electrical conductivity, activation energy of electrical conductivity, and linear thermal expansion coefficient, while thermo-EMF coefficient decreased. Partial substitution of barium by strontium or calcium in BCO leads to the increase in spin-state transition temperature and electrical conductivity of the samples, and, at the same time, thermo-EMF coefficient; consequently, their power factor values decrease

Влияние замещения висмута неодимом и железа марганцем на диэлектрические свойства перовскитного феррита висмута

Bi1-xNdxFe1-xMnxO3 solid solutions have been synthesized, their lattice constants have been determined and their dielectric properties have been studied. It has been established that substitution of bismuth and iron by neodymium and manganese, respectively, leads to the unit cell contraction of Bi1-xNdxFe1-xMnxO3 solid solutions, increase of their electrical conductivity and, consequently, increase of their dielectric losses. Electrical conductivity activation energies for Bi1-xNdxFe1-xMnxO3 de-crease with x , leading to the conclusion that joint substitutions Nd3+ → Bi3+ and Mn3+ → Fe3+ in BiFeO3 facilitate the electri-cal transport in Bi1-xNdxFe1-xMnxO3 solid solutions.Синтезированы твердые растворы Bi1-xNdxFe1-xMnxO3, определены параметры их кристаллической структуры, изучены диэлектрические свойства. Установлено, что замещение ионов висмута и железа ионами неодима и марганца соответственно приводит к сжатию элементарной ячейки твердых растворов Bi1-xNdxFe1-xMnxO3, увеличению их электропроводности и, как следствие, к возрастанию диэлектрических потерь. Энергия активации электропроводности Bi1-xNdxFe1-xMnxO3 с ростом x уменьшается, из чего можно заключить, что совместное замещение Nd3+ → Bi3+, Mn3+ → Fe3+ в BiFeO3 облегчает электроперенос в твердых растворах Bi1-xNdxFe1-xMnxO3

Синтез, структура и свойства твердых растворов на основе слоистого кобальтита кальция

The (Ca,M)3Co4O9+δ (M = Na, Cu, Pb, Bi) solid solutions have been synthesized, their lattice constants have been determined and their electric conductivity and thermo-EMF were studied in 300-1100 K temperature interval. It has been found that Ca2,8Pb0,2Co4O9+δ solid solution possessed the greatest thermo-EMF coefficient of 0,32 mV/K at 1100 K. Activation energies of electrical conductivity and power factor of ceramics studied have been calculated.Синтезированы твердые растворы (Ca,M)3Co4O9+δ (M = Na, Cu, Pb, Bi), определены параметры их кристаллической структуры, в интервале температур 300-1100 К изучены их электропроводность и термо-ЭДС. Установлено, что наибольшим значением коэффициента термо-ЭДС характеризуется твердый раствор Ca2,8Pb0,2Co4O9+δ - 0,32 мВ/К при температуре 1100 К. Рассчитаны значения энергии активации электропроводности и фактора мощности исследованной керамики

Layered Oxygen-Deficient Double Perovskites as Promising Cathode Materials for Solid Oxide Fuel Cells

Development of new functional materials with improved characteristics for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) is one of the most important tasks of modern materials science. High electrocatalytic activity in oxygen reduction reactions (ORR), chemical and thermomechanical compatibility with solid electrolytes, as well as stability at elevated temperatures are the most important requirements for cathode materials utilized in SOFCs. Layered oxygen-deficient double perovskites possess the complex of the above-mentioned prop-erties, being one of the most promising cathode materials operating at intermediate temperatures. The present review summarizes the data available in the literature concerning crystal structure, thermal, electrotransport-related, and other functional properties (including electrochemical performance in ORR) of these materials. The main emphasis is placed on the state-of-art approaches toimproving the functional characteristics of these complex oxides. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: Dr. A.I. Klyndyuk thanks to the Ministry of Education of Belarus Republic, contract no. 20062703, and to the Belarusian Republican Foundation for Fundamental Research, grant no. C3M–049. Dr. D.A. Medvedev thanks to the Ministry of Education and Science of the Russian Federation, contract no. 075-03-2021-051/5

Magnetic and Electrical Properties of Ordered 112-type Perovskite LnBaCoMnO5+\delta (Ln = Nd, Eu)

Investigation of the oxygen-deficient 112-type ordered oxides of the type LnBaCoMnO5+\delta (Ln = Nd, Eu) evidences certain unusual magnetic behavior at low temperatures, compared to the LnBaCo2O5+\delta cobaltites. One observes that the substitution of manganese for cobalt suppresses the ferromagnetic state and induces strong antiferromagnetic interactions. Importantly, NdBaCoMnO5.9 depicts a clear paramagnetic to antiferromagnetic type transition around 220 K, whereas for EuBaCoMnO5.7 one observes an unusual magnetic behavior below 177 K which consists of ferromagnetic regions embedded in an antiferromagnetic matrix. The existence of two sorts of crystallographic sites for Co/Mn and their mixed valence states favor the ferromagnetic interaction whereas antiferromagnetism originates from the Co3+-O-Co3+ and Mn4+-O-Mn4+ interactions. Unlike the parent compounds, the present Mn-substituted phases do not exhibit prominent magnetoresistance effects in the temperature range 75-400K.Comment: 23 pages including figure

Влияние взаимозамещения редкоземельных элементов наструктуру и свойства твердых растворов (Pr, Nd, Sm)BaCoFe5+δ

Using the solid-state reaction method, (Pr,Nd,Sm)BaCoFeO5+δ solid solutions have been synthesized, their lattice constants and oxygen nonstoichiometry have been determined and their thermal expansion and electrical properties have been studied. It has been found that (Pr,Nd,Sm)BaCoFeO5+δ solid solutions show positive deviations from ideality and their structural parameters, thermal and electrotransport properties can be controlled by intersubstitution of rare earth elements in their structure.Твердофазным методом синтезированы твердые растворы (Pr, Nd, Sm)BaCoFeO5+δ, определены параметры их кристаллической структуры и кислородная нестехиометрия, изучены их тепловое расширение и электрические свойства. Установлено, что твердые растворы (Pr, Nd, Sm)BaCoFeO5+δ характеризуются положительными отклонениями от идеальности, а их структурными параметрами, тепловыми и электротранспортными свойствами можно управлять путем направленного взаимозамещения РЗЭ в их структуре

СИНТЕЗ И СВОЙСТВА НИОБИЙ- И КОБАЛЬТЗАМЕЩЕННЫХ ТВЕРДЫХ РАСТВОРОВ ТИТАНАТА ВИСМУТА СО СТРУКТУРОЙ СЛОИСТОГО ПЕРОВСКИТА

The Bi4Ti3–2xNbxCoxO12 (x = 0.05, 0.10, 0.15) solid solutions have been synthesized using ceramic method, their crystal structure, thermal expansion, electrical and dielectric properties have been studied. It has been established that Bi4Ti3–2xNbxCoxO12 titanates are p-type semiconductors whose electrical conductivity at low temperatures is higher, but at high temperatures is lower than for the base Bi4Ti3O12 bismuth titanate. It has been found that partial co-substitution of titanium by niobium and cobalt in Bi4Ti3O12 leads to the increase in the size of the unit cell of the Bi4Ti3–2xNbxCoxO12 solid solutions, a decrease in their Curie temperature, a decrease in the dielectric constant and dielectric losses, and slightly affects the magnitude of their linear thermal expansion coefficient. For Bi4Ti3.8Nb0.1Co0.1O12 and Bi4Ti3.7Nb0.15Co0.15O12 solid solutions, a sharp increase in the activation energy of electrical conductivity has been observed at the transition from the ferroelectric region to the paraelectric region.Керамическим методом синтезированы твердые растворы Bi4Ti3–2xNbxCoxO12 (x = 0,05, 0,10, 0,15), изучены их кристаллическая структура, тепловое расширение, электрические и диэлектрические свойства. Установлено, что титанаты Bi4Ti3–2xNbxCoxO12 являются полупроводниками p-типа, величина электропроводности которых при низких температурах выше, а при повышенных – ниже, чем для базового титаната висмута Bi4Ti3O12. Найдено, что частичное совместное замещение титана ниобием и кобальтом в Bi4Ti3O12 приводит к увеличению размера элементарной ячейки образующихся при этом твердых растворов, снижению их температуры Кюри, уменьшению диэлектрической проницаемости и диэлектрических потерь и слабо влияет на величину их температурного коэффициента линейного расширения. Для твердых растворов Bi4Ti3,8Nb0,1Co0,1O12 и Bi4Ti3,7Nb0,15Co0,15O12 обнаружено резкое возрастание энергии активации электропроводности при переходе из сегнетоэлектрической области в параэлектрическую

Электрохимическое легирование кислороддефицитных оксидов YBa2Cu3O7-x и PrBaCuFeO5+x серой

Sulfur as a heteroadditive has been incorporated into oxygen-deficient YBa2Cu307-x and PrBaCuFeO5+x perovskites (ODP) using sulfur-ion-conducting solid electrolytes (CaPr2S4 and BaSm2S4). Composition of ODPs doped by sulfur was monitored by measuring electrical conductivity in combination with EMF method. The mechanism of sulfur incorporation into crystal lattice of nonstoichiometric layered YBa2Cu307-x and PrBaCuFeO5+x ODP has been proposed. Partial molar dissolution values of sulfur trace amounts in PrBaCuFeO5+x have been calculated.Проведено электрохимическое введение гетеропримеси - серы - в кислороддефицитные перовскиты (КДП) YBa2Cu3O7-x и PrBaCuFeO5+x с помощью сульфидионпроводящих твердых электролитов (CaPr2S4 и BaSm2S4). Контроль за составом легированных серой КДП осуществляли методом электропроводности в сочетании с методом ЭДС. Предложен механизм встраивания серы в кристаллическую решетку нестехиометрических слоистых КДП YBa2Cu3O7-x и PrBaCuFeO5+x. Рассчитаны парциальные молярные величины растворения микроколичеств серы в PrBaCuFeO5+