| 1. |
- Gamage, Eranga H., et al.
(författare)
-
As-Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe-Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering
- 2022
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:25, s. 11283-11295
-
Tidskriftsartikel (refereegranskat)abstract
- A novel mixed-valent hybrid chiral and polar compound, Fe7As3Se12(en)(6)(H2O), has been synthesized by a single-step solvothermal method. The crystal structure consists of 1D [Fe5Se9] chains connected via [As3Se2]-Se pentagonal linkers and charge-balancing interstitial [Fe(en)(3)](2+) complexes (en = ethylenediamine). Neutron powder diffraction verified that interstitial water molecules participate in the crystal packing. Magnetic polarizability of the produced compound was confirmed by X-ray magnetic circular dichroism (XMCD) spectroscopy. X-ray absorption spectroscopy (XAS) and Fe-57 Mossbauer spectroscopy showed the presence of mixed-valent Fe2+/Fe3+ in the Fe-Se chains. Magnetic susceptibility measurements reveal strong antiferromagnetic nearest neighbor interactions within the chains with no apparent magnetic ordering down to 2 K. Hidden short-range magnetic ordering below 70 K was found by Fe-57 Mossbauer spectroscopy, showing that a fraction of the Fe3+/Fe2+ in the chains are magnetically ordered. Nevertheless, complete magnetic ordering is not achieved even at 6 K. Analysis of XAS spectra demonstrates that the fraction of Fe3+ in the chain increases with decreasing temperature. Computational analysis points out several competing ferrimagnetic ordered models within a single chain. This competition, together with variation in the Fe oxidation state and additional weak intrachain interactions, is hypothesized to prevent long-range magnetic ordering.
|
|
| 2. |
- Lee, Kathleen, et al.
(författare)
-
GeAs : Highly Anisotropic van der Waals Thermoelectric Material
- 2016
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 28:8, s. 2776-2785
-
Tidskriftsartikel (refereegranskat)abstract
- GeAs and Sn-doped GeAs were synthesized from elements. Both crystallize in a layered crystal structure in the C2/m space group (No. 12) in the GaTe structure type. The crystal structure consists of As-terminated layers separated by van der Waals gaps. Sn-119 Mossbauer spectroscopy reveals that in the doped compound, Sn atoms are situated in a symmetric and homogeneous environment, most probably in the form of Sn-2 dumbbells. The anisotropic crystal structure of GeAs leads to highly anisotropic transport properties. High electrical and thermal conductivities were determined along the crystallographic layers. For the perpendicular direction across the layers, a sharp drop of more than an order of magnitude was observed for the transport properties of the GeAs single crystal. As a result, an order of magnitude difference in the figure of merit, ZT, was achieved: High-temperature thermoelectric characterization of the Sn-doped compound reveals a remarkable ZT with a maximum of 0.35 at 660 K.
|
|
| 3. |
- Lindsjö, Martin, et al.
(författare)
-
Novel Compounds Sn14In10P22I8 and Sn14In10P21.2I8 with Clathrate-I Structure: Synthesis and Crystal and Electronic Structure
- 2001
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 161:2, s. 232-242
-
Tidskriftsartikel (refereegranskat)abstract
- Two new supramolecular pnictidehalides Sn10In14P22I8 (I) anti Sn14In10P21.2I8 (II) have been synthesized using a standard ampoule technique. Both compounds possess the clathrate I type of structure. I crystallizes in the cubic space group Pm (3) over barn (No. 223) with the unit cell parameter a = 11.0450(7) (Z = 1) while II reveals a complicated superstructure (space group P4(2)/m (No. 84), a = 24.745(3) Angstrom, c = 11.067(1) Angstrom, Z = 5) resulting from the partial ordering of vacancies at phosphorus sites. The crystal structures have been solved based on single-crystal X-ray diffraction data sets (omega -2 theta) scans, least-squares refinement against F-2) to R = 0.0376 (Sn10In14P22I8) and R = 0.0569 (Sn14In10P21.2I8). In both structures metal anti phosphorus atoms form a cationic clathrate I framework hosting iodine atoms in the cavities. The composition of both phases complies with the Zintl-Klemm formalism which justifies the existence of vacancies in the structure of II. The Sn-119 Mossbauer spectroscopy data together with the results of the band structure calculations suggest that the electron density on tin atoms is reduced in favor of bands, which lie just below the Fermi level and must define electronic properties of the compounds in question. The differences in the crystal and electronic structures of the cationic tin clathrates are discussed.
|
|
| 4. |
- Pecunia, Vincenzo, et al.
(författare)
-
Roadmap on energy harvesting materials
- 2023
-
Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
-
Tidskriftsartikel (refereegranskat)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
|
|
