CuSbS2 was tested as a negative electrode material for sodium-ion batteries. The material synthesized by ball milling offers a specific charge of 730 mAh g−1, close to the theoretical value ...(751 mAh g−1), over a few cycles. The reaction mechanism was investigated by means of operando X-ray diffraction, 121Sb Mössbauer spectroscopy, and Cu K-edge X-ray absorption spectroscopy. These studies reveal a sodiation mechanism that involves an original conversion reaction in two steps, through the formation of a ternary phase, CuSb(1−x)S(2−y), as well as a NaxS alloy and Sb, followed by an alloying reaction involving the previously formed Sb. The desodiation process ends with the reformation of the ternary phase, CuSb(1−x′)S(2−y′), deficient in Sb and S; this phase is responsible for the good reversibility observed upon cycling.
•A ternary phase CuSbS2 is tested as anode material for sodium ion batteries.•Reversible specific charge of 730 mAh g−1 for few cycles without optimization.•Combination of conversion and alloying reactions mechanism.
Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of ∼10 GPa. This phenomenon is attributed to a change in the ...electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L
-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.
Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of ∼10 GPa. This phenomenon is attributed to a change in the ...electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L3-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.
Strong magnetic couplings are generally observed intramolecularly in organic diradicals or in systems in which they are promoted by crystal engineering strategies involving, for example, transition ...metal ligation. We herein present a strong intermolecularly coupling verdazyl radical in the solid state without the use of such design strategies. The crystal structure of an acetylene-substituted verdazyl radical shows a unique antiparallel face-to-face orientation of the neighboring verdazyl molecules along with verdazyl-acetylene interactions giving rise to an alternating antiferromagnetic Heisenberg chain. Single crystal structural data at 80, 100, 173, and 223 K show that one of the π-stacking distances depends on temperature, while heat capacity data indicate the absence of a phase transition. Based on this structural input, broken symmetry DFT calculations predict a change from an alternating linear Heisenberg chain with two comparable coupling constants J
and J
at higher temperatures towards dominant pair interactions at lower temperatures. The predicted antiferromagnetic coupling is confirmed experimentally by magnetic susceptibility, solid-state EPR and NMR spectroscopic results.
BaFe2Se3 (Pnma, CsAg2I3-type structure), recently assumed to show superconductivity at ∼11 K, exhibits a pressure-dependent structural transition to the CsCu2Cl3-type structure (Cmcm space group) ...around 60 kbar, as evidenced from pressure-dependent synchrotron powder diffraction data. Temperature-dependent synchrotron powder diffraction data indicate an evolution of the room-temperature BaFe2Se3 structure towards a high-symmetry CsCu2Cl3 form upon heating. Around 425 K BaFe2Se3 undergoes a reversible, first-order isostructural transition, which is supported by the differential scanning calorimetry data. The temperature-dependent structural changes occur in two stages, as determined by the alignment of the FeSe4 tetrahedra and corresponding adjustments of the positions of Ba atoms. On further heating, a second-order phase transformation into the Cmcm structure is observed at 660 K. A rather unusual combination of isostructural and second-order phase transformations is parameterized within phenomenological theory assuming high-order expansion of the Landau potential. A generic phase diagram mapping observed structures is proposed on the basis of the parameterization.
A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph ...crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V2O3 polymorph. At ∼50 K a paramagnetic to canted antiferromagnetic transition is detected.
Polycrystalline Ce3Pd4Sn6 samples were synthesized by arc-melting and subsequent annealing at 970 K. Specific heat, electrical resistivity and magnetic susceptibility measurements are performed over ...a wide range in temperature and provide hints for the presence of a complex magnetic ordering below 3 K arising from three crystallographically independent Ce sites. This behaviour is driven by a complex interplay between ferro-, ferri-, and antiferromagnetic correlations among the Ce atoms.
The lithium-ion battery electrode material TiSnSb shows excellent electrochemical performance related to its high capacity (550 mA h g–1) and rate capability over 210 cycles. To discriminate between ...the role of active material and the role of the electrode formulation in the good electrochemical features of the TiSnSb electrodes, a full study comparing the electrochemical mechanisms of TiSnSb and a Ti/Sn/Sb composite vs Li is undertaken by combining X-ray diffraction (XRD), 121Sb, 119Sn Mössbauer and 7Li NMR spectroscopic in situ measurements. During the first discharge, TiSnSb undergoes a direct conversion reaction while Ti/Sn/Sb composites proceed by a stepwise alloying process, both leading to a mixture of lithium antimonide, lithium stannides, and titanium. More surprisingly the charge occurs differently with a reformation of the “TiSnSb” phase in the first case and the formation of Sn and Sb in the second case. The key role of the interfaces in conversion type reactions is discussed. The nature of the interfaces is linked to the long-range order of elements in the starting material. Furthermore, the length scales of the interfaces between Li3Sb, Li x Sn and Ti appear to control the reactions that occur on charge.
The low-temperature heat capacity of knorringite garnet (Mg
3
Cr
2
Si
3
O
12
) was measured between 2 and 300 K, and thermochemical functions were derived from the results. The measured heat capacity ...curves show a sharp lambda-shaped anomaly peaking at around 5.1 K. Magnetic susceptibility data show that the transition is caused by antiferromagnetic ordering. From the
C
p
data, we suggest a standard entropy (298.15 K) of 301 ± 2.5 J mol
−1
K
−1
for Mg
3
Cr
2
Si
3
O
12
. The new data are also used in conjunction with previous experimental results to constrain ∆
H
f
° for knorringite.
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