Stability of High-Spin State of Iron in β-NaFeO2

We investigated the stability of the high-spin state of the iron β-NaFeO2 based on the structural refinement. The oxidation of the Fe2+ ion in the as-synthesized sample is evidenced by its green color. Due to its sensitivity in air and CO2, this compound will decompose into a reddish Fe3+ state. The smaller crystal volume of the decomposed compound is mainly related to the shorter ionic radius of the high-spin state Fe3+ and this result will be compared to the single crystal sample. In contrast to the polycrystalline sample, the decomposition single crystal sample only taking place on the surface of the as-grown crystal.

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Crystal structure refinement of MnTe2, MnSe2, and MnS2: cation-anion and anion–anion bonding distances in pyrite-type structures

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2018-2134 ◽

2019 ◽

Vol 234 (6) ◽

pp. 371-377 ◽

Cited By ~ 3

Author(s):

Makoto Tokuda ◽

Akira Yoshiasa ◽

Tsutomu Mashimo ◽

Hiroshi Arima ◽

Hidetomo Hongu ◽

...

Keyword(s):

Single Crystal ◽

Spin State ◽

Structure Refinement ◽

Mean Square Displacement ◽

Structural Refinement ◽

X Ray Diffraction ◽

X Ray ◽

Structural Differences ◽

The Mean ◽

The Stability

Abstract The stability of hauerite (MnS2) as compared to that of pyrite (FeS2) can be explained by the long Mn–S distance and departure from the typical pyrite-type structures. The structural differences of MnX2 compounds (X=S, Se, and Te) are the result of spin configurations that are different than those of other MX2 compounds; however, the arrangement of d-electrons and the size of the ions in MnX2 compounds do not clearly explain why Mn2+ in MnX2 does not exist as a low spin state. To investigate the structural differences of MnX2 compounds, we synthesized single-crystal MnTe2 and MnSe2 and performed single-crsytal X-ray diffraction experiments. The single-crystal X-ray diffraction experiments were conducted on MnTe2 [a=6.9513(1) Å, u-parameter=0.38554(2), space group Pa3̅, Z=4], MnSe2 [a=6.4275(2) Å, u-parameter=0.39358(2)], MnS2 [hauerite; a=6.1013(1) Å, u-parameter=0.40105(4), obtained from Osorezan, Aomori, Japan], and FeS2 [pyrite; a=5.4190(1) Å, u-parameter 0.38484(5), obtained from Kawarakoba, Nagasaki, Japan]. The X-ray intensity datasets of these compounds do not show any evidence of symmetry reduction. In MnS2, the S–S distance is 2.0915(8) Å, which is significantly shorter than that of FeS2 (2.1618(9) Å), and the mean square displacement of S (U11=0.00915(9) Å2) is smaller than that of Mn (U11=0.01137(9) Å2). The thermal vibration characteristics of MnX2 compounds are significantly different than those of FeS2. Based on structural refinement data, we discuss the low spin state of MnX2 compounds and the structural stability of pyrite-type structures.

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The superconducting transition and mixed state of YBa2Cu3O6.95: an undergraduate experiment

European Journal of Physics ◽

10.1088/1361-6404/ac405f ◽

2021 ◽

Author(s):

Zhongda Huang ◽

Yihang Tong ◽

Jake Bobowski

Keyword(s):

Magnetic Susceptibility ◽

Single Crystal ◽

Mixed State ◽

High Temperature Superconductors ◽

Polycrystalline Sample ◽

Single Crystal Sample ◽

Base Temperature ◽

Superconducting Transition ◽

Temperature Drift ◽

Crystal Sample

Abstract We describe a simple AC susceptometer built in-house that can be used to make high-resolution measurements of the magnetic susceptibility of high-temperature superconductors in an undergraduate physics lab. Our system, cooled using liquid nitrogen, can reach a base temperature of 77 K. Our apparatus does not require gas handling systems or PID temperature controllers. Instead, it makes use of a thermal circuit that is designed to allow the sample to cool on a time scale that is suitable for an undergraduate lab. Furthermore, the temperature drift rate at the superconducting transition temperature T c is low enough to allow for precise measurements of the complex magnetic susceptibility through T c, even for single-crystal samples with exceedingly sharp superconducting transitions. Using an electromagnet, we were able to apply static magnetic fields up to 63 mT at the sample site. By measuring the change in susceptibility as a function of the strength of an applied of static magnetic field, we were able to estimate the lower critical field H c1 of a single-crystal sample of optimally-doped YBa2Cu3O6.95 at 77 K. We also investigated the mixed state of a sintered polycrystalline sample of YBa2Cu3O6+y .

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First study of the photo-induced metastable (paramagnetic) high-spin state in a [Fe(ptz) 6 ](BF 4 ) 2 single crystal by polarised neutron diffraction

Polyhedron ◽

10.1016/s0277-5387(03)00161-x ◽

2003 ◽

Vol 22 (14-17) ◽

pp. 2155-2160 ◽

Cited By ~ 7

Author(s):

Jelena Jeftić ◽

Béatrice Gillon ◽

Antoine Goujon ◽

Quitterie Nau ◽

Arsen Gukasov ◽

...

Keyword(s):

Neutron Diffraction ◽

Single Crystal ◽

High Spin ◽

Spin State ◽

High Spin State

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Crystal chemistry of K-rich nepheline in nephelinite from Hamada, Shimane Prefecture, Japan

Mineralogical Magazine ◽

10.1180/mgm.2018.133 ◽

2018 ◽

Vol 83 (02) ◽

pp. 239-247 ◽

Cited By ~ 1

Author(s):

Maki Hamada ◽

Masahide Akasaka ◽

Hiroaki Ohfuji

Keyword(s):

Single Crystal ◽

Diffraction Data ◽

Structural Formula ◽

Single Crystal Sample ◽

Structural Refinement ◽

X Ray Diffraction ◽

Crystal Sample ◽

X Ray ◽

Incommensurate Structure ◽

Absolute Structure

AbstractK-rich nepheline with a structural formula of A2B6T14T24T34T44O32 (Z = 1) within melilite–olivine nephelinite from Hamada, Shimane Prefecture, Japan, was investigated to clarify its crystal structure and to determine cation distributions in the A and B structural positions of structural channels and tetrahedral T1–T4 sites. The chemical formula of a single-crystal sample was (Na5.437K2.248Mg0.034Ca0.031)Σ7.750(Si8.332Al7.445Fe3+0.158Ti0.009Cr0.005)Σ15.949O32, which results in 65.2, 27.8, 2.1, 3.2 and 1.6 mol.% NaAlSiO4, KAlSiO4, NaFe3+SiO4, □Si2O4 and □0.5(Ca,Mg)0.5AlSiO4 end-member components, respectively, where □ is a vacancy. X-ray diffraction data of a single crystal with dimensions of 0.28 mm × 0.15 mm × 0.05 mm measured at 296 K indicate the space group P63. In the structural refinement, the R1 factor was reduced to 3.69% by taking twinning by merohedry into the refinement. The refinement accounted for 77.7% of the absolute structure and 22.3% of the a and b axes reversed absolute structure. The atomic populations determined in the A and B positions were 1.834 K + 0.166 □ and 5.705 Na + 0.198 K + 0.031 Ca + 0.034 Mg, respectively, implying the substitution of K for Na in the B position. The a and c dimensions are a = 10.0270(3) and c = 8.4027(3) Å. The average <A–O> and <B–O> distances are 3.009 and 2.65 Å, respectively. The substitution of K for Na in the B channel results in increased volume and bond-length distortion of the BO8 polyhedra, which then reduces distortion of the AO9 polyhedra. The average T–O distances indicate that the T1 and T4 sites are essentially filled with Al, whereas the T2 and T3 are filled with Si. Despite the deviation of the O1 oxygen from the triad axis and the combination of K+ ions and vacancies in the hexagonal channels, an incommensurate structure was not observed in the X-ray diffraction data or using the electron diffraction technique.

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Stability and equation of state of face-centered cubic and hexagonal close packed phases of argon under pressure

Scientific Reports ◽

10.1038/s41598-021-93995-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Agnès Dewaele ◽

Angelika D. Rosa ◽

Nicolas Guignot ◽

Denis Andrault ◽

João Elias F. S. Rodrigues ◽

...

Keyword(s):

Equation Of State ◽

Single Crystal ◽

Single Crystal Sample ◽

Moderate Pressure ◽

Face Centered Cubic ◽

Experimental Conditions ◽

Crystal Sample ◽

Hexagonal Close Packed ◽

Face Centered ◽

Fcc Phase

AbstractThe compression of argon is measured between 10 K and 296 K up to 20 GPa and and up to 114 GPa at 296 K in diamond anvil cells. Three samples conditioning are used: (1) single crystal sample directly compressed between the anvils, (2) powder sample directly compressed between the anvils, (3) single crystal sample compressed in a pressure medium. A partial transformation of the face-centered cubic (fcc) phase to a hexagonal close-packed (hcp) structure is observed above 4.2–13 GPa. Hcp phase forms through stacking faults in fcc-Ar and its amount depends on pressurizing conditions and starting fcc-Ar microstructure. The quasi-hydrostatic equation of state of the fcc phase is well described by a quasi-harmonic Mie–Grüneisen–Debye formalism, with the following 0 K parameters for Rydberg-Vinet equation: $$V_0$$ V 0 = 38.0 Å$$^3$$ 3 /at, $$K_0$$ K 0 = 2.65 GPa, $$K'_0$$ K 0 ′ = 7.423. Under the current experimental conditions, non-hydrostaticity affects measured P–V points mostly at moderate pressure ($$\le$$ ≤ 20 GPa).

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Extending the temperature sensing range using Eu3+ luminescence up to 865 K in a single crystal of EuPO4

Physical Chemistry Chemical Physics ◽

10.1039/c9cp03501j ◽

2019 ◽

Vol 21 (29) ◽

pp. 16329-16336 ◽

Cited By ~ 7

Author(s):

Suchinder K. Sharma ◽

Thomas Köhler ◽

Jan Beyer ◽

Margret Fuchs ◽

Richard Gloaguen ◽

...

Keyword(s):

Single Crystal ◽

Temperature Sensing ◽

Single Crystal Sample ◽

Coupling Scheme ◽

Excitation Wavelength ◽

Crystal Sample ◽

Sensing Range

Extending the temperature sensing range up to 865 K using an appropriate choice of excitation wavelength and coupling scheme in a single crystal sample of EuPO4.

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