SrFe12O19 AS AN IMPURITY IN PEROVSKITE-TYPE FERRITES

A decrease of oxygen content in SrFe12O19 and its subsequent decomposition were studied by coulometric titration. The significant release of oxygen during stepwise decomposition can be considered as a specific characteristic of SrFe12O19.Работа выполнена по теме № AAAA-A19-119031890026-6 ИХТТ УрО РАН

DEFECT CHEMISTRY STUDY IN PEROVSKITE FERRITES CONTAMINATED WITH SrFe12O19

A strong negative effect of SrFe12O19 impurity presence in perovskite-type ferrites on the results of the coulometric titration has been revealed. A method has been developed to deter-mine the amount of impurity and recover the oxygen content data in perovskite ferrites con-taminated with SrFe12O19

The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described

Tubular thermoelectric module based on oxide elements grown by the laser floating zone

This work seeks possibilities for advancing the thermoelectric oxide technology by exploring a module design involving materials produced by laser processing. A tubular thermoelectric generator of modular construction with functional elements located parallel to a pipe-shaped heat source was designed and manufactured. The p- and n-type counterparts based on Ca3Co4O9 and Ca0.95Pr0.05MnO3 were grown by the laser floating zone (LFZ) technique, ensuring highly dense microstructures and giving the unique possibility for fast and crucible-free processing of the legs with desirable geometry. The detailed structural and microstructural characterization indicated that the LFZ processing should be accompanied with an additional thermal annealing step to equilibrate the phase composition. Although the measured electrical performance was found close to or slightly higher compared to that of similar materials produced by other routes, it was still notably suppressed by the remaining phase impurities affecting the module's output. The maximum observed power output of the module containing 12 Ca3Co4O9/Ca0.95Pr0.05MnO3 thermoelectric couples reached up to 20 mW at a temperature gradient of 389 °C and a hot side temperature of 525 °C. The contribution of various factors to the overall performance was analyzed. The results suggest that the power output could be significantly enhanced by decreasing the contact resistance at the cold side and proper optimization of the LFZ processing conditions.publishe

Structure and transport properties of La0.5Sr0.5 (-) xCaxFeO3 (-) (delta)

Effects of calcium doping on the structure, dimensional stability, and mixed oxygen-ion and electron conductivity of perovskite-like La0.5Sr0.5 - xCaxFeO3 - delta(x = 0-0.3) were studied in light of potential membrane applications. The incorporation of relatively small Ca2+ cations into the lanthanum-strontium ferrite lattice decreases unit cell volume, oxygen nonstoichiometry variations and chemical contribution to the thermal expansion in air. These changes correlate with rising tendency to local oxygen-vacancy ordering and the formation of nano-sized domains with the brownmillerite and LaCa2Fe3O8-type lattices, as revealed by electron diffraction. The resultant vacancy trapping, changing domain structure and enlargement of the interfacial boundary area lead to non-linear relationships between the partial ion conductivity and cation composition, while the apparent activation energy for ion transport at temperatures below 900 degrees C remains almost constant, 0.6-0.7 eV. The n-type electron contribution to the total conductivity, measured in the oxygen pressure range 10(-20)-0.5 atm at 700-950 degrees C, is also essentially independent of the calcium concentration. (C) 2013 Elsevier B.V. All rights reserved

First observation of the magnetic dipole CO₂ absorption band at 3.3 µm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument

International audienceThe atmosphere of Mars is dominated by CO2, making it a natural laboratory for studying CO2 spectroscopy. The Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter uses solar occultation geometry to search for minor atmospheric species. During the first year of ACS observations, the attention was focused on the spectral range covering the methane ν3 absorption band, 2900–3300 cm−1, which has previously been observed on Mars. No methane was detected by ACS; instead, an improvement of the data processing has led to the identification of 30 weak absorption lines that were missing from spectroscopic databases. Periodic series of absorptions up to ~1.6% deep are observed systematically around the position of the methane Q-branch when the line of sight penetrates below 20 km (creating an optical path length of 300–400 km, with an effective pressure of a few millibar). The observed frequencies of the discovered lines match theoretically computed positions of the P-, Q-, and R-branches of the magnetic dipole and electric quadrupole 01111-00001 (ν2 + ν3) absorption bands of the main CO2 isotopologue; neither band has been measured or computed before. The relative depths of the observed spectral features support the magnetic dipole origin of the band. The contribution of the electric quadrupole absorption is several times smaller. Here we report the first observational evidence of a magnetic dipole CO2 absorption