Magnetic and electronic properties of layered Sr2NiO2Cl2 with square planar coordination

Zhou, Wenqi; Li, Shuwei; Wu, Shuxiang

doi:10.1016/j.jmmm.2020.167195

Cited by 4 publications

(6 citation statements)

References 36 publications

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“…For e g state, it further splits into d z 2 and d x 2 – y 2 orbitals. The square‐planar coordination makes d x 2 – y 2 orbital the highest energy 70,65 . A large bandgap generates from the divergence of the t 2g and e g state, as shown in Figure S5.…”

Section: Resultsmentioning

confidence: 99%

“…For Sr 2 MO 2 Cu 2 Se 2 , the infinite [MO 2 ] 2− square-planar sheets (Figure 2C) and [Cu 2 Se 2 ] 2− layers stack along the c-axis separated by Sr 2+ . The infinite [MO 2 ] 2− sheets were also observed in Sr 2 MO 2 X 2 (M = Co, Ni; X = Cl, Br) [61][62][63][64][65] (see Figure 2B). As the M sites change from Mn to Zn, compared to rigid [Sr 2 MO 2 ] 2+ layers, the [Cu 2 Se 2 ] 2− layers are easily distorted with the change of lattice constant.…”

Section: Theoretical Calculationsmentioning

confidence: 93%

“…To further investigate the origin of thermopowers, we calculated the band structure of Sr 2 orbital the highest energy. 70,65 A large bandgap generates from the divergence of the t 2g and e g state, as shown in Figure S5. Thus, for 3d 8 Ni 2+ ions, the d z 2 and d x 2 -y 2 states are unoccupied, whereas others are fully occupied.…”

Section: Band Structurementioning

confidence: 99%

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Thermoelectric properties of layered oxyselenides with 3d transition metal ions

et al. 2023

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Layered oxychalcogenides have received extensive attention in the fields of magnetism, superconductivity, lithium battery, and luminescence due to their unique electronic, magnetic properties, and layered structure, among which layered oxyselenides have excellent and promising thermoelectric performance, such as BiCuSeO and Bi2LnO4Cu2Se2. Here, we successfully synthesized Sr2MO2Cu2Se2 (M = Co, Ni, Zn) and Sr2FeO3CuSe and investigated the thermoelectric properties at a wide temperature range (298–923 K). They have a relatively high Seebeck coefficient (>300 μV K−1) in medium to high temperature range and possess a low thermal conductivity. The power factor and ZT reach 65 μW m−1 K−1 and 0.07 at 923 K for intrinsic Sr2NiO2Cu2Se2, and a higher performance is expected to be achieved by strategies like carrier concentration optimization and band structure engineering.

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Section: Resultsmentioning

confidence: 99%

Section: Theoretical Calculationsmentioning

confidence: 93%

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Thermoelectric properties of layered oxyselenides with 3d transition metal ions

et al. 2023

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“…The values of U eff were set to 5 eV for Fe and 7 eV for Ni, respectively, on the basis of previous studies. [61,62] Supporting Information Supporting Information is available from the Wiley Online Library or from the author.…”

Section: Methodsmentioning

confidence: 99%

Accelerating Oxygen Evolution Reaction Kinetics by Reconstructing Layered and Defective Ni₃FeOOH/FeOOH in a Hematite Photoanode

et al. 2023

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Surface engineering has outstanding advantages for improving the carrier exaction of photoelectrodes in the photoelectrochemical water splitting field. NiFe‐layered double hydroxides (NiFe‐LDH), as promising catalysts for water oxidation, can facilitate carrier transport. But surface collapse and structural deformation limit their applications. In this work, a hematite (α‐Fe2O3) photoanode is sequentially cumulatively modified with NiFe‐LDH (Ni3FeOOH), Ag/SiO2, and FeOOH, and exhibits a high photocurrent density, which increases from 0.92 to 4.54 mA cm−2 at 1.23 V relative to the standard hydrogen electrode (VRHE). The mechanism studies demonstrate that the introduction of FeOOH suppresses the electrochemical self‐reduction of Ni3FeOOH, remedies the obvious valley formed in the current density and voltage curve, reduces recombination, and facilitates the OH− transformation, which increases the catalytic activities of the photoanode. The Ag@SiO2 nanoparticles can reduce the interface defects between Ni3FeOOH and FeOOH. The density‐functional theory calculation reveals that the valley is caused by the direction of the internal electric field formed between Ni3FeOOH and α‐Fe2O3, which is opposite to that of solid–liquid junction, resulting in serious carrier recombination. FeOOH possesses a higher electrostatic potential than that of Ni3FeOOH and α‐Fe2O3 and forms an internal electric field directing from α‐Fe2O3/Ni3FeOOH to FeOOH, which synergistically promotes carrier separation with solid–liquid junction.

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“…This is supported by the magnetic susceptibility which shows a distinctive feature at 210 K, suggestive of a long-range magnetic order, that is, high-spin Ni 2+ . This state is predicted computationally, although such ordering has not been probed experimentally using PND to the best of our knowledge.…”

Section: Resultsmentioning

confidence: 93%

High- versus Low-Spin Ni²⁺ in Elongated Octahedral Environments: Sr₂NiO₂Cu₂Se₂, Sr₂NiO₂Cu₂S₂, and Sr₂NiO₂Cu₂(Se_1–xS_x)₂

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Blandy

et al. 2022

Chem. Mater.

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Sr 2 NiO 2 Cu 2 Se 2 , comprising alternating [Sr 2 NiO 2 ] 2+ and [Cu 2 Se 2 ] 2− layers, is reported. Powder neutron diffraction shows that the Ni 2+ ions, which are in a highly elongated NiO 4 Se 2 environment with D 4h symmetry, adopt a high-spin configuration and carry localized magnetic moments which order antiferromagnetically below ∼160 K in a √2a × √2a × 2c expansion of the nuclear cell with an ordered moment of 1.31(2) μ B per Ni 2+ ion. The adoption of the high-spin configuration for this d 8 cation in a pseudo-squareplanar ligand field is supported by consideration of the experimental bond lengths and the results of density functional theory (DFT) calculations. This is in contrast to the sulfide analogue Sr 2 NiO 2 Cu 2 S 2 , which, according to both experiment and DFT calculations, has a much more elongated ligand field, more consistent with the low-spin configuration commonly found for square-planar Ni 2+ , and accordingly, there is no evidence for magnetic moment on the Ni 2+ ions. Examination of the solid solution Sr 2 NiO 2 Cu 2 (Se 1−x S x ) 2 shows direct evidence from the evolution of the crystal structure and the magnetic ordering for the transition from high-spin selenide-rich compounds to low-spin sulfide-rich compounds as a function of composition. Compression of Sr 2 NiO 2 Cu 2 Se 2 up to 7.2 GPa does not show any structural signature of a change in the spin state. Consideration of the experimental and computed Ni 2+ coordination environments and their subtle changes as a function of temperature, in addition to transitions evident in the transport properties and magnetic susceptibilities in the end members, Sr 2 NiO 2 Cu 2 Se 2 and Sr 2 NiO 2 Cu 2 S 2 , suggest that simple high-spin and low-spin models for Ni 2+ may not be entirely appropriate and point to further complexities in these compounds.

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Magnetic and electronic properties of layered Sr2NiO2Cl2 with square planar coordination

Cited by 4 publications

References 36 publications

Thermoelectric properties of layered oxyselenides with 3d transition metal ions

Thermoelectric properties of layered oxyselenides with 3d transition metal ions

Accelerating Oxygen Evolution Reaction Kinetics by Reconstructing Layered and Defective Ni₃FeOOH/FeOOH in a Hematite Photoanode

High- versus Low-Spin Ni²⁺ in Elongated Octahedral Environments: Sr₂NiO₂Cu₂Se₂, Sr₂NiO₂Cu₂S₂, and Sr₂NiO₂Cu₂(Se_1–xS_x)₂

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Magnetic and electronic properties of layered Sr2NiO2Cl2 with square planar coordination

Cited by 4 publications

References 36 publications

Thermoelectric properties of layered oxyselenides with 3d transition metal ions

Thermoelectric properties of layered oxyselenides with 3d transition metal ions

Accelerating Oxygen Evolution Reaction Kinetics by Reconstructing Layered and Defective Ni3FeOOH/FeOOH in a Hematite Photoanode

High- versus Low-Spin Ni2+ in Elongated Octahedral Environments: Sr2NiO2Cu2Se2, Sr2NiO2Cu2S2, and Sr2NiO2Cu2(Se1–xSx)2

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Accelerating Oxygen Evolution Reaction Kinetics by Reconstructing Layered and Defective Ni₃FeOOH/FeOOH in a Hematite Photoanode

High- versus Low-Spin Ni²⁺ in Elongated Octahedral Environments: Sr₂NiO₂Cu₂Se₂, Sr₂NiO₂Cu₂S₂, and Sr₂NiO₂Cu₂(Se_1–xS_x)₂