Journal of Physical Chemistry C
·
2023
·
IF 3.7
Miao Miao Zhao,Lei Meng,Yi Yang Xu,Na Du,Fei Yen
While all of the polymorphs of NH4I and NH4Br are nonpolar, a reversible electric polarization is established in the ordered γ phases of (NH4)0.73(ND4)0.27I and (NH4)0.84(ND4)0.16Br (where D is 2H) via dc electric fields. The presence of two groups of orbital magnetic moments appears to be responsible for the asymmetric lattice distortions. Our findings provide an alternative pathway for hydrogen-based materials to potentially add a ferroelectric functionality.
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry C
·
2019
·
IF 4.309
Fei Yen,Lei Meng,Tian Gao,Sixia Hu
Different types of magnetism arise mainly from how electrons move and interact with each other. In this work, we show how protons (H+) also exhibit magnetic behavior. We measured the magnetic susceptibility of the ammonium halides and identified pronounced increases at 232, 233, and 243 K for NH4I, NH4Br, and NH4Cl, respectively, all of which coincide with the geometric ordering of their ammonium cations. With extensive literature establishing the fact that the ammonium cations exhibit rotational motion even toward the lowest temperatures, we take into account that the orbital motion of the protons carries a magnetic moment and find it to be larger than that of the paired electrons. Consequently, the structural phase transitions are magnetically driven as the system attempts to lift 8-fold energy degeneracies of the proton orbitals via Jahn–Teller distortions. Our findings identify that NH4+ cations are capable of comprising magnetism which appears to be ubiquitous in ammonia-based molecular solids.
研究领域:
物理学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2023
·
IF 6.2
Yi Yang Xu,Lei Meng,Miao Miao Zhao,Chu Xin Peng,Fei Yen
While all of the polymorphs of pure NH 4 I and KI are non-polar, we identify that (NH 4 ) 0.95 K 0.05 I is ferroelectric and (NH 4 ) 0.87 K 0.13 I and (NH 4 ) 0.83 K 0.17 I are pyroelectric through measurements of their pyroelectric current and complex dielectric constant. The order to disorder phase transitions occur near 245 K. Magnetic susceptibility measurements indicate that the proton orbitals of the NH 4 + continue to become ordered in the ground state in the (NH 4 ) 1–x K x I system up to x ≤ 0.17. The polar phases are proposed to stem from K + ions disrupting the symmetry of proton-orbital-lattice interactions between the NH 4 + and I – ions. Our work introduces a new pathway for the ordered phases of ammonium-based compounds to potentially become ferroelectric.
研究领域:
材料科学
·
凝聚态物理
✓ 已验证
DOI
高影响因子
Nature Communications
·
2022
·Vol. 13
·期 1
·1-9
·
IF 17.694
Ren Qingyong,Qi Ji,Yu Dehong,Zhang Zhe,Song Ruiqi,Song Wenli,Yuan Bao,Wang Tianhao,Ren Weijun,Zhang Zhidong,Tong Xin,Li Bing
One of the greatest obstacles to the real application of solid-state refrigeration is the huge driving fields. Here, we report a giant barocaloric effect in inorganic NH 4 I with reversible entropy changes of \(\Delta {S}_{{P}_{0}\to P}^{{{\max }}}\) ∼ 71 J K −1 kg −1 around room temperature, associated with a structural phase transition. The phase transition temperature, T t , varies dramatically with pressure at a rate of d T t /d P ∼ 0.79 K MPa −1 , which leads to a very small saturation driving pressure of Δ P ∼ 40 MPa, an extremely large barocaloric strength of \(\left|\Delta {S}_{{P}_{0}\to P}^{{{\max }}}/\Delta P\right|\) ∼ 1.78 J K −1 kg −1 MPa −1 , as well as a broad temperature span of ∼ 41 K under 80 MPa. Comprehensive characterizations of the crystal structures and atomic dynamics by neutron scattering reveal that a strong reorientation-vibration coupling is responsible for the large pressure sensitivity of T t . This work is expected to advance the practical application of barocaloric refrigeration.
研究领域:
材料科学
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热力学
·
制冷工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2020
·
IF 10.652
Pengcheng Shi,Xin Liang,Kun Xu,Yi Sun,Sheng Cheng,Chunhua Chen,Hongfa Xiang
Li 2 S is highly desired for high energy-density lithium sulfur batteries since it allows to be matched with Li metal-free anodes and alleviates the volume expansion of S cathode. However, Li + extraction from Li 2 S usually suffers from a huge voltage barrier due to its poor electron conductivity and sluggish Li + ion diffusion during activation. In this work, trace sulfone-assisted-NH 4 I is adopted as an electrolyte additive with synergistic dissolution and catalysis effects to alleviate the voltage barrier of Li 2 S. On one hand, the intercalation between sulfone-NH 4 + and Li 2 S turns solid Li 2 S into liquid phase, which significantly speeding up the transport of electrons and Li + ions during activation. On the other hand, I − works as a redox mediator, which further facilitates the oxidation of Li 2 S to polysulfides. By taking the advantages of synergistic dissolution and catalysis effects from sulfone-NH 4 + and I − , the Li 2 S cathode can be activated at ~3.0 V with a very flat plateau. Finally, the Li 2 S cathode cycled in the electrolyte with optimized 0.5% sulfone-assisted-NH 4 I additive shows a high initial discharge capacity of 1160 mAh g −1 at 0.05C, along with enhanced cycling performances and rate capabilities.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）