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1. X-ray diffraction and density functional theory studies of R(Fe0.5Co0.5)O3 (R = Pr, Nd, Sm, Eu, Gd)

   https://doi.org/10.1017/S088571561600049X  

   Wong-Ng, W. ; Liu, G. ; Levin, I. ; Williamson, I. ; Ackerman, P. ; Talley, K. R. ; Martin, J. ; AlHamdan, K. ; Badegaish, W. ; Kaduk, J. A. ; et al ( December 2016 , Powder Diffraction)

   The structure of a series of lanthanide iron cobalt perovskite oxides, R (Fe 0.5 Co 0.5 )O 3 ( R = Pr, Nd, Sm, Eu, and Gd), have been investigated. The space group of these compounds was confirmed to be orthorhombic Pnma (No. 62), Z = 4. From Pr to Gd, the lattice parameter a varies from 5.466 35(13) Å to 5.507 10(13) Å, b from 7.7018(2) to 7.561 75(13) Å, c from 5.443 38(10) to 5.292 00(8) Å, and unit-cell volume V from 229.170(9) Å 3 to 220.376(9) Å 3 , respectively. While the trend of V follows the trend of the lanthanide contraction, the lattice parameter “ a ” increases as the ionic radius r ( R 3+ ) decreases. X-ray diffraction (XRD) and transmission electron microscopy confirm that Fe and Co are disordered over the octahedral sites. The structure distortion of these compounds is evidenced in the tilt angles θ, ϕ , and ω , which represent rotations of an octahedron about the pseudocubic perovskite [110] p , [001] p , and [111] p axes. All three tilt angles increase across the lanthanide series (for R = Pr to R = Gd: θ increases from 12.3° tomore »15.2°, ϕ from 7.5° to 15.8°, and ω from 14.4° to 21.7°), indicating a greater octahedral distortion as r ( R 3+ ) decreases. The bond valence sum for the sixfold (Fe/Co) site and the eightfold R site of R (Fe 0.5 Co 0.5 )O 3 reveal no significant bond strain. Density Functional Theory calculations for Pr(Fe 0.5 Co 0.5 )O 3 support the disorder of Fe and Co and suggest that this compound to be a narrow band gap semiconductor. XRD patterns of the R (Fe 0.5 Co 0.5 )O 3 samples were submitted to the Powder Diffraction File.« less
2. Sr _1-x Ca _x Fe _1-y Co _y O _3-δ as facile and tunable oxygen sorbents for chemical looping air separation

   https://doi.org/10.1088/2515-7655/ab7cb0  

   Dou, Jian ; Krzystowczyk, Emily ; Wang, Xijun ; Richard, Anthony R. ; Robbins, Thomas ; Li, Fanxing ( April 2020 , Journal of Physics: Energy)

   Chemical looping air separation (CLAS) is a promising technology for oxygen generation with high efficiency. The key challenge for CLAS is to design robust oxygen sorbents with suitable redox properties and fast redox kinetics. In this work, perovskite-structured Sr_1-xCa_xFe_1-yCo_yO₃oxygen sorbents were investigated and demonstrated for oxygen production with tunable redox properties, high redox rate, and excellent thermal/steam stability. Cobalt doping at B site was found to be highly effective, 33% improvement in oxygen productivity was observed at 500 °C. Moreover, it stabilizes the perovskite structure and prevents phase segregation under pressure swing conditions in the presence of steam. Scalable synthesis of Sr_0.8Ca_0.2Fe_0.4Co_0.6O₃oxygen sorbents was carried out through solid state reaction, co-precipitation, and sol-gel methods. Both co-precipitation and sol-gel methods are capable of producing Sr_0.8Ca_0.2Fe_0.4Co_0.6O₃sorbents with satisfactory phase purity, high oxygen capacity, and fast redox kinetics. Large scale evaluation of Sr_0.8Ca_0.2Fe_0.4Co_0.6O₃, using an automated CLAS testbed with over 300 g sorbent loading, further demonstrated the effectiveness of the oxygen sorbent to produce 95% pure O₂with a satisfactory productivity of 0.04 g_O2g_sorbent⁻¹h⁻¹at 600 °C.
3. Synthesis of lead-free Cs ₄ (Cd _1−x Mn _x )Bi ₂ Cl ₁₂ (0 ≤ x ≤ 1) layered double perovskite nanocrystals with controlled Mn–Mn coupling interaction

   https://doi.org/10.1039/D0NR06771G  

   Yang, Hanjun ; Shi, Wenwu ; Cai, Tong ; Hills-Kimball, Katie ; Liu, Zhenyang ; Dube, Lacie ; Chen, Ou ( November 2020 , Nanoscale)

   Lead-free perovskites and their analogues have been extensively studied as a class of next-generation luminescent and optoelectronic materials. Herein, we report the synthesis of new colloidal Cs 4 M( ii )Bi 2 Cl 12 (M( ii ) = Cd, Mn) nanocrystals (NCs) with unique luminescence properties. The obtained Cs 4 M( ii )Bi 2 Cl 12 NCs show a layered double perovskite (LDP) crystal structure with good particle stability. Density functional theory calculations show that both samples exhibit a wide, direct bandgap feature. Remarkably, the strong Mn–Mn coupling effect of the Cs 4 M( ii )Bi 2 Cl 12 NCs results in an ultra-short Mn photoluminescence (PL) decay lifetime of around 10 μs, around two orders of magnitude faster than commonly observed Mn 2+ dopant emission in NCs. Diluting the Mn 2+ ion concentration through forming Cs 4 (Cd 1−x Mn x )Bi 2 Cl 12 (0 < x < 1) alloyed LDP NCs leads to prolonged PL lifetimes and enhanced PL quantum yields. Our study provides the first synthetic example of Bi-based LDP colloidal NCs with potential for serving as a new category of stable lead-free perovskite-type materials for various applications.
4. Three to tango requires a site-specific substitution: hetero tri metallic molecular precursors for high-voltage rechargeable batteries

   https://doi.org/10.1039/c8sc03816c  

   Han, Haixiang ; Wei, Zheng ; Filatov, Alexander S. ; Carozza, Jesse C. ; Alkan, Melisa ; Rogachev, Andrey Yu. ; Shevtsov, Andrey ; Abakumov, Artem M. ; Pak, Chongin ; Shatruk, Michael ; et al ( January 2019 , Chemical Science)

   Design of hetero tri metallic molecules, especially those containing at least two different metals with close atomic numbers, radii, and the same coordination number/environment is a challenging task. This quest is greatly facilitated by having a heterobimetallic parent molecule that features multiple metal sites with only some of those displaying substitutional flexibility. Recently, a unique heterobimetallic complex LiMn 2 (thd) 5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been introduced as a single-source precursor for the preparation of a popular spinel cathode material, LiMn 2 O 4 . Theoretical calculations convincingly predict that in the above trinuclear molecule only one of the Mn sites is sufficiently flexible to be substituted with another 3d transition metal. Following those predictions, two hetero tri metallic complexes, LiMn 2−x Co x (thd) 5 ( x = 1 ( 1a ) and 0.5 ( 1b )), that represent full and partial substitution, respectively, of Co for Mn in the parent molecule, have been synthesized. X-ray structural elucidation clearly showed that only one transition metal position in the trinuclear molecule contains Co, while the other site remains fully occupied by Mn. A number of techniques have been employed for deciphering the structure and composition of hetero tri metallic compounds.more »Synchrotron resonant diffraction experiments unambiguously assigned 3d transition metal positions as well as provided a precise “site-specific Mn/Co elemental analysis” in a single crystal, even in an extremely difficult case of severely disordered structure formed by the superposition of two enantiomers. DART mass spectrometry and magnetic measurements clearly confirmed the presence of hetero tri metallic species LiMnCo(thd) 5 rather than a statistical mixture of two hetero bi metallic LiMn 2 (thd) 5 and LiCo 2 (thd) 5 molecules. Heterometallic precursors 1a and 1b were found to exhibit a clean decomposition yielding phase-pure LiMnCoO 4 and LiMn 1.5 Co 0.5 O 4 spinels, respectively, at the relatively low temperature of 400 °C. The latter oxide represents an important “5 V spinel” cathode material for the lithium ion batteries. Transmission electron microscopy confirmed a homogeneous distribution of transition metals in quaternary oxides obtained by pyrolysis of single-source precursors.« less
5. Optical thermal insulation via the photothermal effects of Fe ₃ O ₄ and Fe ₃ O ₄ @Cu _2−x S thin films for energy-efficient single-pane windows

   https://doi.org/10.1557/mrc.2020.4  

   Lin, Jou ; Zhao, Yuan ; Shi, Donglu ( March 2020 , MRS Communications)

   To address critical energy issues in civic structures, we have developed a novel concept of optical thermal insulation (OTI) without relying on a conventional thermal intervention medium, such as air or argon, as often used in conventional window systems. We have synthesized the photothermal (PT) materials, such as the Fe 3 O 4 and Fe 3 O 4 @Cu 2− x S nanoparticles, that exhibit strong UV and near-infrared (NIR) absorptions but with good visible transparency. Upon coating the inner surface of the window glass with a PT film, under solar irradiation, the inner surface temperature rises due to the PT effect. Subsequently, the temperature difference, Δ T , is reduced between the single pane and room interior. This leads to lower the thermal loss through a window, reflected by the U -factor, resulting in considerable energy saving without double- or triple-glazing. Comparing with the Fe 3 O 4 coatings, Fe 3 O 4 @Cu 2− x S is spectrally characterized with a much stronger NIR absorbance, contributing to an increased PT efficiency under simulated solar irradiation (0.1 W/cm 2 ). PT experiments are carried out via both white light and monochromic NIR irradiations (785 nm). The parameters associated withmore »the thermal performance of the PT films are calculated, including PT conversion efficiency, specific absorption rate (SAR), and U -factor. Based on the concept of OTI, we have reached an optimum U -factor of 1.46 W/m 2 K for a single pane, which is satisfactory to the DOE requirement (<1.7 W/m 2 K).« less