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A new ternary phase has been synthesized and structurally characterized. BaLi x Cd 13– x ( x ≈ 2) adopts the cubic NaZn 13 structure type (space group Fm 3 ¯ c , Pearson symbol cF 112) with unit cell parameter a = 13.5548 (10) Å. Structure refinements from single-crystal X-ray diffraction data demonstrate that the Li atoms are exclusively found at the centers of the Cd 12 -icosahedra. Since a cubic BaCd 13 phase does not exist, and the tetragonal BaCd 11 is the most Cd-rich phase in the Ba–Cd system, BaLi x Cd 13– x ( x ≈ 2) has to be considered as a true ternary compound. As opposed to the typical electron count of ca. 27 e -per formula unit for many known compounds with the NaZn 13 structure type, BaLi x Cd 13– x ( x ≈ 2) only has ca. 26 e -, suggesting that both electronic and geometric factors are at play. Finally, the bonding characteristics of the cubic BaLi x Cd 13– x ( x ≈ 2) and tetragonal BaCd 11 are investigated using the TB-LMTO-ASA method, showing metallic-like behavior.
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Measurement of the crystallization and phase transition of niobium dioxide thin-films using a tube furnace optical transmission system
Niobium dioxide has a volatile memristive phase change that occurs ∼800 °C that makes it an ideal candidate for future neuromorphic electronics. A straightforward optical system has been developed on a horizontal tube furnace for in situ spectral measurements as an as-grown Nb2O5 film is annealed and ultimately crystallizes as NbO2. The system measures the changing spectral transmissivity of Nb2O5 as it undergoes both reduction and crystallization processes. We were also able to measure the transition from metallic-to-non-metallic NbO2 during the cooldown phase, which is shown to occur about 100 °C lower on a sapphire substrate than fused silica. After annealing, the material properties of the Nb2O5 and NbO2 were assessed via x-ray photoelectron spectroscopy, x-ray diffraction, and 4-point resistivity, confirming that we have made crystalline NbO2.
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- PAR ID:
- 10597516
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- AIP Advances
- Volume:
- 14
- Issue:
- 11
- ISSN:
- 2158-3226
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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