Chemical strain in perovskite-like materials

Pseudo-cubic perovskites based upon substituted oxides RBO3-δ as well as double perovskites RBaB2O6-δ and Sr2BMoO6, where R=rare-earth element and B=3d-transition metal, with A-site and B-site, respectively, cation ordering are very promising materials for a variety of different devices for moderate high temperature applications. The unique feature of the oxides is their ability to undergo both thermal strain and that induced by the defects of oxygen nonstoichiometry in the oxide crystal lattice. The latter is called as chemical or defect-induced strain, which is extremely sensitive to the defect structure of the oxide material. This property was shown recently to be isotropic for pseudo-cubic perovskites unlike that of double perovskites. The crystal lattice of a double perovskite expands along a-axis and simultaneously contracts along c-axis with the decreasing lattice oxygen content. The model of the oxide lattice chemical strain based on a change of mean ionic radius due to reduction of most reducible cation has been recently developed by us. In this work we introduced the new feature in the model such as change of preferable coordination of cations caused by change of oxygen content in the oxide. The modified model was shown to enable correct prediction of chemical expansion upon increasing oxygen nonstoichiometry along a-axis for both pseudo-cubic and double perovskite oxides and simultaneous lattice contraction along c-axis in double perovskites. Thus most important finding is that simultaneous lattice contraction along c-axis in double perovskites is caused by aforementioned change of preferable coordination

Experimental thermochemical verification of trends in thermodynamic stability of hybrid perovskite-type organic-inorganic halides

Hybrid perovskite-type methylammonium lead halides have received great attention in recent years due to high conversion efficiency obtained in solar cells based on such materials. Since the time of the first demonstration photovoltaic devices based on the hybrid perovskites CH3NH3PbX3 (X = Cl, Br, I) have showed huge progress in increase of conversion efficiency reaching currently 20.1%. However, despite very promising achievements fundamental chemistry and physics of hybrid organic-inorganic (HOIP) perovskites is far from being completely understood. In particular it is true for thermodynamic properties of HOIP perovskite-type halides ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I). Moreover, reported results of DFT calculations aiming at estimating the stability of these materials often give controversial results. In addition, some of the HOIP perovskites (for example, CH3NH3PbX3 (X = Cl, Br, I)) are known to be entropy-stabilized phases. Therefore experimental verification of the stability trends in HOIP perovskite-type halide systems is strongly required. This is especially important for assessment of the stability of these materials under particular working conditions. Therefore, the main aim of this work was to study the thermodynamics of formation of HOIP perovskite-type halides ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I). Their standard formation enthalpy at 298 K was measured by solution calorimetry. Heat capacity was measured in the temperature range 2-298 K using PPMS system. Standard entropy was obtained by integration of the Cp/T vs T curve. Standard Gibbs free energy of ABX3 and A2BX4 (A=CH3NH3, formamidinium, Cs, Rb, etc; B=Sn, Pb, 3d-element; X = Cl, Br, I) was evaluated using measured formation enthalpy and entropy. Trends in variation of the thermodynamic functions with chemical composition and crystal structure of HOIP perovskite-type halides were analyzed and compared with available results of DFT calculations. This work was supported by the Russian Science Foundation (grant No. 18-73-10059)

Hydration thermodynamics of proton-conducting perovskite Ba4Ca2Nb2O11

The oxygen nonstoichiometry index δ, i.e. number of oxygen vacancies per formula unit, in perovskite-type BaCa(1+y)/3Nb(2-y)/3O3–δ (BCNy) oxides can be tailored by varying the Ca–Nb ratio y, and equals . These oxygen vacancies can be hydrated under humid atmosphere, providing nonstoichiometric BCNy oxides with good proton conductivity. It makes them promising materials for proton-conducting solid oxide fuel cell (SOFC) electrolytes and high-temperature humidity sensors. The present work aimed to partly address the lack of fundamental thermodynamic studies on BCNy by investigating the heat of low-temperature hydration-induced phase transition as well as the higher-temperature thermodynamics of hydration and related defect chemistry of BCN50 oxide. Please click Additional Files below to see the full abstract

In situ and ex situ study of cubic La0.5Ba0.5CoO3–δ to double perovskite LaBaCo2O6– δ transition

Double perovskites REBaCo2O6–δ (RE – rare-earth element) have received great attention in past decades as promising materials for various electrochemical devices because of their high mixed ionic-electronic conductivity and catalytic activity for the reaction of oxygen reduction. Among these compounds, cobaltite LaBaCo2O6–δ can serve as a good example of structural flexibility, since it is able to form either A-site disordered cubic “simple” perovskite or layered A-site ordered double perovskite. However, the exact limits of the thermodynamic stability of LaBaCo2O6–δ double perovskite with respect to temperature (T) and oxygen partial pressure (pO2) have not been determined so far. Furthermore, synthesis and study of selected properties of either cubic or layered LaBaCo2O6–δ oxide were mostly of interest for researchers, whereas the transition from “simple” to double perovskite was not addressed in detail so far. At the same time, it is generally recognized that such transition significantly improves oxide ion transport in the perovskite-type oxides and, therefore, understanding this order-disorder transition is of key importance for successful development of new materials for practical application. Therefore, the present work aims at providing some insights into the nature of the aforementioned order-disorder transformation of LaBaCo2O6–δ, as well as into thermodynamic stability of both ordered and disordered phases, using a set of complementary techniques such as transmission electron microscopy, in situ X-ray diffraction and solid state coulometric titration. As a result, formation of complex domain textured intermediate products during the phase transition “ordered LaBaCo2O6–δ – disordered La0.5Ba0.5CoO3–δ” was revealed. These products were found to exhibit strong affinity to oxygen and fast oxygen exchange with ambient atmosphere even at temperature as low as 70 °C. This particularity seems to provide a unique possibility to develop a new class of advanced materials for IT SOFCs, ceramic membranes and catalysis. The thermodynamic stability limits of the cubic and double perovskites were determined as log(pO2) = f(1/T) dependencies. The stability diagram of the LaBaCo2O6–δ – La0.5Ba0.5CoO3–δ system was plotted as a result. Oxygen nonstoichiometry of the thermodynamically stable cubic perovskite La0.5Ba0.5CoO3–δ was measured as a function of pO2 in temperature range between 1000 and 1100 °C using coulometric titration technique. Acknowledgement: This study was supported by the Russian Foundation for Basic Research (Grant No. 18-33-20243)

Biogeographic patterns of planktonic and meiobenthic fauna diversity in inland waters of the Russian Arctic

Broad-scale assessment of biodiversity is needed for detection of future changes across substantial regions of the Arctic. Presently, there are large data and information gaps in species composition and richness of the freshwater planktonic and meiobenthos communities of the Russian Arctic. Analysis of these data is very important for identifying the spatial distribution and temporal changes in species richness and diversity of rotifers, cladocerans, and copepods in the continental Russian Arctic. We investigated biogeographic patterns of freshwater plankton and meiobenthos fromc. 67 degrees to 73 degrees N by analysing data over the period 1960-2017. These data include information on the composition of rotifers, cladocerans, and copepods obtained from planktonic and meiobenthic samples, as well as from subfossil remains in bottom sediments of seven regions from the Kola Peninsula in the west, to the Indigirka River Basin (east Siberia) in the east. Total richness included 175 species comprised of 49 rotifer genera, 81 species from 40 cladoceran genera, and 101 species from 42 genera of calanoid, cyclopoid, and harpacticoid copepods. Longitudinal trends in rotifer and micro-crustacean diversity were revealed by change in species composition from Europe to eastern Siberia. The most common and widespread species were 19 ubiquitous taxa that includedKellicottia longispina(Rotifera),Chydorus sphaericuss. lat. (Cladocera),Heterocope borealis,Acanthocyclops vernalis, andMoraria duthiei(Copepoda). The highest number of rare species was recorded in the well-studied region of the Bolshezemelskaya tundra and in the Putorana Plateau. The total number of copepod and rotifer species in both Arctic lakes and ponds tended to increase with latitude. Relative species richness of copepods was positively associated with waterbody area, elevation, and precipitation, while relative species richness of cladocerans was positively related to temperature. This result is consistent with known thermophilic characteristics of cladocerans and the cold tolerance properties of copepods, with the former being dominant in shallow, warmer waterbodies of some western regions, and the latter being dominant in large cold lakes and waterbodies of eastern regions. Rotifers showed a negative association with these factors. Alpha- and beta-diversity of zooplankton in the Russian Arctic were strongly related to waterbody type. Lake zooplankton communities were more diverse than those in pond and pool systems. Moreover, the highest beta-diversity values were observed in regions that showed a greater breadth in latitude and highly heterogeneous environmental conditions and waterbody types (Bolshezemelskaya tundra and Putorana Plateau). Redistribution of freshwater micro-fauna caused by human activities occurred in the 1990s and 2000s. As a result of climate warming, a few cladoceran species appear to have extended their range northward. Nevertheless, the rotifer and micro-crustacean fauna composition and diversity of the majority of Arctic regions generally remain temporally conservative, and spatial differences in composition and species richness are chiefly associated with the differences between the warmer European and colder east Siberian climates.Peer reviewe

Crystal structure, oxygen nonstoichiometry, hydration and conductivity BaZr1- xMxO3-d (M=Pr, Nd, Y, Co)

Partially substituted perovskite-like barium zirconates with general formula BaZr1-хМхО3-d possess oxygen-ion and proton conductivity and, therefore, may be promising as electrolytes for intermediate temperature solid oxide fuel cells. The aim of this work was to study the crystal structure, thermal and chemical expansion, water uptake, oxygen nonstoichiometry, total conductivity and Seebeck coefficient of zirconates BaZr1-xMxO3-d (M=Pr, Nd, Y, Co) in the atmospheres with different levels of humidity (log(pH2O/atm.) = -1.75; -2.5; -3.5) as a function of oxygen partial pressure (log(pO2/atm) = -20 - -0.67) and temperature (T = 25 – 1050 °C). Synthesis of the samples was carried out by glycerol-nitrate method. The phase composition of the as-prepared powders was analyzed by the X-ray diffraction (XRD). Room temperature and high temperature XRD studies were carried out using Shimadzu XRD-7000 diffractometer equipped with high temperature chamber HTK 16N (Anton Paar GmbH). Thermal and chemical expansion was also measured using DIL 402 C dilatometer (Netzsch GmbH). Oxygen nonstoichiometry was studied by solid state coulometric titration and thermogravimetry. Electrical conductivity and Seebeck coefficient were measured simultaneously in the same setup. This work was supported by the Russian Science Foundation (project No.18-73-00022)

Content of Metals in Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. from Water Bodies of Different Salinity

Металлы определяли в двух видах макрофитов – Phragmites australis Trin. ex Steud и Potamogeton pectinatus L., произрастающих в водоемах с разной соленостью, с помощью эмиссионного спектрометра с индуктивно-связанной плазмой. Анализ результатов методом главных компонент показал, что на валовое содержание металлов влияет вид макрофитов и условия окружающей среды, в частности химический состав воды. Оба вида макрофитов из пресноводного водохранилища Бугач отличались более высокими концентрациями железа, алюминия, никеля, ванадия и кобальта по сравнению с теми же видами макрофитов, собранными в солоноватоводных озерах. Однако для макрофитов из оз. Шира, отобранных в опресненной и солоноватоводной частях озера, расхождений в содержании данных металлов не выявлено. В ряде случаев пробы из одной точки, но собранные в разные годы имели существенные различия – это наблюдалось для растений тростника из солоноватоводной станции оз. Шира, и растений рдеста из оз. Шунет. Было установлено, что наиболее высокое валовое содержание большинства металлов характерно для P. pectinatusMetals were determined in two species of macrophytes Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. grown in lakes of different salinity, using emission spectrometer with inductively coupled plasma. Principal component analysis revealed that the total metal content is influenced by species of macrophytes and environmental conditions (in particular water chemistry). Both species of macrophytes from freshwater reservoir Bugach were characterized by higher concentrations of Fe, Al, Ni, V and Co in comparison with the same species from brackish lakes. However, there were no significant differences in content of these metals between samples of macrophytes taken in desalinated and saltwater parts of Shira Lake. In some cases, metal content of samples collected in different years at the same place were significantly different. It was observed for plants of Ph. australis collected in brackish station of Shira Lake, and plants of P. pectinatus from Lake Shunet. It was found that the highest total content of most metals is typical for P. pectinatu

Summer Time Distribution of Sedentary and Migratory Individuals of the Baikal Grayling Thymallus baicalensis in the Tributaries of the Thermally Altered Section of the Yenisei River

Изменение температурного режима Енисея в нижнем бьефе ГЭС создало условия, позволяющие местной популяции байкальского хариуса осуществлять все стадии жизненного цикла в основном русле реки, без необходимости миграции в притоки, роль которых в поддержании популяционной структуры вида остается неизвестной. Целью проведенных в июле-августе 2021 года исследований стала оценка присутствия особей хариуса в пяти различных по протяженности притоках Енисея в районе г. Красноярска, а также их дифференциация по происхождению на основании анализа структуры чешуи и темпов роста. Полученные результаты свидетельствуют о неоднородном пространственном распределении вида в исследованных притоках, где он был представлен как оседлыми особями, так и мигрантами из основного русла Енисея. Область распространения хариуса в июле-августе была ограничена участками рек, температура воды в которых не превышала 16–17 ºС. Жилая медленнорастущая форма обнаружена в верхнем и среднем течении р. Березовка, а также на изолированных дамбами участках верхнего течения р. Кача. В крупных притоках Мана и Базаиха, на значительном удалении от их устья, отмечены мигранты из Енисея, с единичным присутствием оседлых особей. Таким образом, современная популяция байкальского хариуса на термически измененном участке реки Енисей включает рыб с разной миграционной активностью. Несмотря на меньшую биомассу зообентоса в притоках, по сравнению с основным руслом Енисея, преимуществом летней миграции в прогретые притоки может быть удлинение периода соматического роста рыб до 7 месяцевThe changes in the temperature regime of the Yenisei River downstream from the Krasnoyarsk Hydroelectric Power Plant have created conditions which allow the local population of the Baikal grayling to pass through all the stages of its life cycle in the main stream without migrating into the Yenisei tributaries, the role of the latter in maintaining the structure of the grayling population remaining unknown. The present research is aimed to determine the distribution of grayling in five Yenisei tributaries of different lengths in the vicinity of Krasnoyarsk and to investigate fish individuals’ origin based on comparative analysis of scale morphology and growth rate. The results indicate a heterogeneous spatial distribution of the species in the tributaries with both sedentary individuals and migrants from the mainstream of the Yenisei. Grayling distribution through July and August was limited to the river sections with water temperature up to 16–17 ºС. Slowly growing sedentary forms inhabit the upper and middle reaches of the Beryozovka River and the upper reaches of the Kacha River sections isolated by dams. Migrants from the Yenisei and single sedentary individuals were found at a considerable distance from the mouths of larger tributaries, the Mana and Bazaikha. Thus, the current population of the Baikal grayling in the thermally altered section of the Yenisei includes fish with different migration patterns. Although zoobenthos biomass is lower in the tributaries than in the mainstream of the Yenisei, a possible advantage of the summer migration into the warmed tributaries is the prolongation of the somatic growth period up to 7 month