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Thermoelectric oxides are considered as perspective materials for energy conversion due to their high thermal and chemical stability, low cost and environmental compatibility in comparison with the conventional semiconductors based on bismuth and tellurium [1]. Herein we report firstly the thermoelectric properties of composites between perovskite and layered oxides. The proof-of-concept studies conducted on LaCo0.8Ni0.1Fe0.1O3 perovskite and layered Ca3Co4O9 oxides demonstrate the improved thermoelectric properties of composites through the enhancing the boundaries phonon scattering without affecting the electronic transport. The oxide composites are formed by mechanical milling followed by annealing at 900 oC. This procedure allows to achieve a good contact between particles without changing the structure and composition of two components. The thermoelectric efficiency of the composites is determined by the dimensionless figure of merit (ZT) calculated from the independently measured Seebeck coefficient, electrical resistivity and thermal conductivity. The observed changes in the electrical resistivity of the composites are explained by the particle size effects and the contact between particles. It is found that the thermoelectric activity of the composites is higher than that of the individual components.

Herein, we propose a new concept to stabilize oxygen redox activity by using oxygen storage materials as efficient buffer supplying and receiving an oxygen during alkali-ion intercalation. The concept consists in treatment of intercalation oxides, P3-Na2/3Ni1/2Mn1/2O2, with “oxygen-storage” material, namely CeO2. This type of modification with CeO2 does not affect the bulk structure of layered oxide. The modified oxides display drastic increase in the reversible capacity when used as cathodes in Na-, Li- and hybrid Li,Na-ion cells. The highest capacity of about 285 mAh/g is reached for the modified oxide cycled in hybrid Li,Na-ion cell. In addition, CeO2 affects also the inter-phase interaction between electrode and Li/NaPF6 salt electrolyte.

Herein, we demonstrate the temperature-induced reactivity of three-layered oxide: P3-Na2/3Ni1/3Mg1/6Mn1/2O2 (NM16), designed with optimized composition and structure aims to work at elevated temperatures. The electrochemical behavior of P3 Na2/3Ni1/3Mg1/6Mn1/2O2 as a positive electrode is studied in both type of cells – sodium and hybrid lithium-sodium ones, and in presence of conventional carbonate-based and advanced ionic liquids-based (IL) electrolytes. The structural changes and surface reactivity of the layered oxide after cycling are monitored by ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. In sodium cells the layered structure of P3-NM16 during Na+ intercalation is preserved and any significant phase changes are not observed. It is found that at 40 oC, the rate capability of the oxide is improved upon cycling using an IL electrolyte rather than the carbonate-based electrolyte. The IL electrolyte exhibits a low surface reactivity towards layered oxide, irrespective of the operating temperature. The dominant electrolyte-electrode interaction appears to be the adsorption of the electrolyte ions. In contrast, the carbonate-based electrolyte has been shown to be highly reactive, resulting in the formation of interface rich on inorganic and organic decomposition products. In hybrid Li/Na ion cell, the interaction between P3-NM16 and lithium electrolyte begins before the electrochemical reaction, resulting in a transformation of P3 into O3 type of structure. Along with the structural transformation, a film enriched with LiF, NaF, electrolyte-decomposed products grows on the oxide surface. The film composition depends on the operating temperature and with its increasing the decomposed products become denser. The best cycling stability and rate capability is observed when P3-NM16 operates in hybrid Li/Na ion cell using IL-based electrolyte at 40 oC. In addition the performance of the oxide in hybrid Li/Na ion cell is better than that in single sodium-ion cell which emphasizes the advantage of dual Li+,Na+ ion intercalation.

В настоящето изследване ние демонстрираме разработването на състав, който е проектиран да работи при повишени температури. Чрез селективно заместване на Ni2+ йони с Mg2+ в трислойния оксид, P3-Na2/3Ni1/2Mn1/2O2, се контролират степента на окисление на Ni йони, катионно разпределение в слоевете, капацитета на интеркалация на натрий и способността за работа при различни скорости на заряд и разряд. In the present study, we demonstrate the development of a composition that is designed to operate at elevated temperatures. By selective substitution of Ni2+ ions with Mg2+ in the trilayer oxide, P3-Na2/3Ni1/2Mn1/2O2, control the degree of Ni ion oxidation, cation distribution in the layers, the sodium intercalation capacity and the ability to operate at different charge rates and discharge.

The present research is devoted to studying the influence of high oxygen pressure on the thermoelectric properties of cobalt-based perovskites. Two model compositions were selected as the subject of research: mono-substituted with Ni perovskites LaCo0.9Ni0.10O3 and doubly substituted with Ni and Fe perovskites LaCo0.8Ni0.1Fe0.1O3. It is characteristic of them that they show better thermoelectric properties than unsubstituted lanthanum cobaltite. Oxygen pressure was 200 bar and it has a direct effect on the superoxygen content of the perovskite. The structural characteristics of the perovskites were investigated by X-ray structural analysis using the Rietveld method. The thermal properties of the punched calcined under high oxygen pressure were also studied by DTA and TG analyses. Electrical properties were measured on an MMR apparatus (K2500-5SLP-SP) using the Van der Pauw method in a temperature range of 300 to 600 K and a magnetic field of 5 T. All measurements were performed on tablets with minimal porosity. Настоящето изследване е посветено на изучаване на влиянието на високото кислородно налягане върху термоелектричните свойства на перовскити на основата на кобалт. Като обект на изследване са подбрани два моделни състава: еднозаместени с Ni перовскити LaCo0.9Ni0.10O3 и двойнозаместени с Ni и Fe перовскити LaCo0.8Ni0.1Fe0.1O3. Характерно за тях е, че те показват по-добри термоелектрични свойства от незаместения лантанов кобалтит [2]. Кислородно налягане бе 200 bar и то оказва пряко въздействие върху свръхкислородното съдържание на перовскита. Структурните характеристики на перовскитите са изследвани чрез рентгеноструктурен анализ по метода на Ритвелд. Термичните свойства на пробите накалени под високо кислородно налягане бяха проучени и чрез ДТА И ТГ анализи. Електричните свойства са измерени на апаратура MMR (K2500-5SLP-SP) по метода на Van der Pauw в температурния интервал от 300 до 600 K и магнитно поле от 5 T. Всички измервания са извършени на таблетки с минимална порьозност.

In this report, the electrical properties of cobalt oxides with layered and perovskite structures, as well as composites between them, will be compared. The purpose of the research is to study the conditions of formation of composites between perovskites and layered oxides and how they affect their electrical properties. The layered and perovskite oxides were obtained by the methods of soft chemistry by using the Pechini reaction, and the composites by mechanical grinding and annealing. Structural and morphological characteristics were determined by X-ray diffraction and SEM analyses. В настоящия доклад ще бъдат сравнени електричните свойства на кобалтови оксиди със слоеста и перовскитова структури, както и на композити между тях. Целта на изследването е да се изучат условията на формиране на композити между перовскити и слоести оксиди и как те влияят върху електричните им свойства. Слоестите и перовскитни оксиди са получени по методите на меката химия чрез използване на реакцията на Печини, а композитите чрез механично смилане и отгряване. Структурните и морфологични характеристики са определени чрез рентгенова дифракция и СЕМ анализи.

Citrate solution method is very suitable for preparation of multielement perovskites in the form of powders and thin layers. In this study, we demonstrate the feasibility of the method for deposition of perovskite-based materials on conventional γ-alumina and industrial metal carriers. A perovskite-based entity of La(Co0.8Ni0.1Fe0.1)0.85Pd0.15O3 composition manifested a high catalytic activity in the methane combustion reaction. Preliminary data on the practical applicability of the perovskite-based material supported on monolithic VDM®Aluchrom Y Hf carrier are reported. Taking into account the high thermal stability of the catalytically active phase it is concluded that the prepared material can serve as a basis for further development of an effective technology for abatement of methane emissions..