X‐ray fluorescence holography (XFH) is typically performed using zero‐dimensional detectors. This makes data acquisition in synchrotron facilities time consuming. Here, we report the first direct imaging of the X‐ray fluorescence hologram of a Fe3O4 sample using a 2D hybrid detector. The apparatus, data acquisition and data processing are described here. The recorded Fe Kα hologram agreed well with simulations, and the atomic images reconstructed using the SPEA‐L1 algorithm showed agreement with the expected Fe and O positions. Furthermore, by tuning the incident X‐ray energy, fluorescence from the Fe3+ cations can be suppressed, allowing the imaging of Fe Kα holograms from Fe2.5+ cations. The valence‐sensitivity of the holograms was confirmed by the appearance of different sets of Kossel lines in the hologram, and in the atomic reconstructions. Reconstructions from the holograms from Fe2.5+ cations show that these emitters are located on octahedral sites, and the reconstruction from the Fe3+ holograms shows emitters on the tetrahedral sites. These results demonstrate that the new 2D hybrid detector‐based apparatus is a good XFH alternative that can be used to clarify structures of multi‐valence materials. Further applications to radiation‐damage sensitive samples, and even time‐resolved XFH experiments can also be achieved using this new XFH apparatus.
We performed X-ray fluorescence holography measurements on a Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) multiferroic material in order to investigate the temperature dependence of three dimensional local structure around Fe atoms. It was found that the atomic image intensity of the nearest neighbor Pb atom abruptly decreases when the temperature becomes lower than the Néel temperature (T N ) of about 150 K, while the intensity of the atomic image at nearest Fe/Nb position remains almost unchanged. These observations show that the magnetic transition at T N induces static positional shifts of Pb atoms but does not strongly influence the Fe/Nb atoms, which suggests the involvement of Pb ions into the superexchange interaction between Fe ions and its contribution to the spin-lattice coupling in PFN.
With the development of application of wireless sensor
nodes (WSNs),
the need for energy harvesting is rapidly increasing. In this study,
we designed and fabricated a robust monolithic thermoelectric generator
(TEG) using a simple, low-energy, and low-cost device fabrication
process. Our monolithic device consists of Ag2S0.2Se0.8 and Bi0.5Sb1.5Te3 as n-type and p-type legs, respectively, while the empty space between
the legs was filled with highly dense, flexible, and thin Ag2S that serves as both an insulating spacer and a shock absorber,
which potentially augments the robustness of preventing from damage
from an external mechanical force. From the optimization of the device
structure via finite element method (FEM) simulations, a three-pair
device with dimensions of 12 mm × 10 mm × 10 mm was found
to have a theoretical maximum power density of 8.2 mW cm–2 at a ΔT of 50 K. For considering this inevitable
contact resistance, experimental measurement and FEM simulation were
combined for quantifying the junction resistance; a power density
of 2.1 mW cm–2 was established with the consideration
of the contact resistance at the p–n junctions. Using these
optimized structural parameters, a device was fabricated and was found
to have a maximum power density of 2.02 mW cm–2 at
a ΔT of 50 K, which is in good agreement with our
simulations. The results from our monolithic TEG show that despite
the simple, low-energy, and low-cost device fabrication process, the
power generation is still comparable to other reported TEGs. It is
worth mentioning that our design could be extended to other chalcogenide
materials of appropriate temperature regions and/or better zT. Besides, the quantification of contact resistance also
exhibited reference value for the enhancement of thermoelectric conversion
application. These results provide a convenient, economic, and efficient
strategy for waste energy harvesting close to room temperature, which
can broaden the applications of waste heat harvesting.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.