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Gao JX, Ng YS, Cheng H, Wang HQ, Lü TY, Zheng JC. Local symmetry-driven interfacial magnetization and electronic states in (ZnO) n/(w-FeO) n superlattices. Phys Chem Chem Phys 2024; 26:12084-12096. [PMID: 38586994 DOI: 10.1039/d4cp00481g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Superlattices constructed with the wide-band-gap semiconductor ZnO and magnetic oxide FeO, both in the wurtzite structure, have been investigated using spin-polarized first-principles calculations. The structural, electronic and magnetic properties of the (ZnO)n/(w-FeO)n superlattices were studied in great detail. Two different interfaces in the (ZnO)n/(w-FeO)n superlattices were identified and they showed very different magnetic and electronic properties. Local symmetry-driven interfacial magnetization and electronic states can arise from different Fe/Zn distributions at different interfaces or spin ordering of Fe in the superlattice. The local symmetry-driven interfacial magnetization and electronic states, originating either from different Fe/Zn distribution across interfaces I and II, or by spin ordering of Fe in the superlattice, can be identified. It was also found that, in the case of the ferromagnetic phase, the electrons are more delocalized for the majority spin but strongly localized for the minority spin, which resulted in interesting spin-dependent transport properties. Our results will pave the way for designing novel spin-dependent electronic devices through the construction of superlattices from semiconductors and multiferroics.
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Affiliation(s)
- Jia-Xin Gao
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Yi Sheng Ng
- Department of New Energy Science and Engineering, Xiamen University Malaysia, Sepang 43900, Malaysia
| | - Hao Cheng
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, China
| | - Hui-Qiong Wang
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, China.
- Department of New Energy Science and Engineering, Xiamen University Malaysia, Sepang 43900, Malaysia
| | - Tie-Yu Lü
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Jin-Cheng Zheng
- Engineering Research Center of Micro-nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, China.
- Department of New Energy Science and Engineering, Xiamen University Malaysia, Sepang 43900, Malaysia
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Zhang W, Du FY, Dai Y, Zheng JC. Strain engineering of Li + ion migration in olivine phosphate cathode materials LiMPO 4 (M = Mn, Fe, Co) and (LiFePO 4) n(LiMnPO 4) m superlattices. Phys Chem Chem Phys 2023; 25:6142-6152. [PMID: 36752130 DOI: 10.1039/d2cp05241e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The olivine phosphate family has been widely utilized as cathode materials for high-performance lithium-ion batteries. However, limited energy density and poor rate performance caused by low electronic and ionic conductivities are the main obstacles that need to be overcome for their widespread application. In this work, atomic simulations have been performed to study the effects of lattice strains on the Li+ ion migration energy barrier in olivine phosphates LiMPO4 (M = Mn, Fe, Co) and (LiFePO4)n(LiMnPO4)m superlattices (SLs). The (LiFePO4)n(LiMnPO4)m superlattices include three ratios of LFP/LMP, namely SL3 + 1, SL1 + 1 and SL1 + 3, each of which is along three typical (100), (010) and (001) orientations. We mainly discuss two migration paths of Li+ ions: the low-energy path A channel parallel to the b-axis and the medium-energy path B channel parallel to the c-axis. It is found that the biaxial tensile strain perpendicular to the migration path is most beneficial to reduce the migration energy barrier of Li+ ions, and the strain on the b-axis has a dominant effect on the energy barrier of Li+ ion migration. For path A, SL3 + 1 alternating periodically along the (010) orientation can obtain the lowest Li ion migration energy barrier. For path B, SL1 + 3 is the most favorable for Li+ ion migration, and there is no significant difference among the three orientations. Our work provides reference values for cathode materials and battery design.
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Affiliation(s)
- Wang Zhang
- Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Fu-Ye Du
- Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Yang Dai
- Department of Chemical Engineering, School of Environmental and Chemical Engineering, Shanghai University, Shangda Road 99, Shanghai 200444, China.
| | - Jin-Cheng Zheng
- Department of Physics, Xiamen University, Xiamen 361005, China. .,Department of Physics, and Department of New Energy Science and Engineering, Xiamen University Malaysia, Sepang 43900, Malaysia
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Abstract
How to achieve high thermoelectric figure of merit is still a scientific challenge. By solving the Boltzmann transport equation, thermoelectric properties can be written as integrals of a single function, the transport distribution function (TDF). In this work, the shape effects of transport distribution function in various typical functional forms on thermoelectric properties of materials are systematically investigated. It is found that the asymmetry of TDF, characterized by skewness, can be used to describe universally the trend of thermoelectric properties. By defining symmetric and asymmetric TDF functions, a novel skewness is then constructed for thermoelectric applications. It is demonstrated, by comparison with ab initio calculations and experiments, that the proposed thermoelectric skewness not only perfectly captures the main feature of conventional skewness but also is able to predict the thermoelectric power accurately. This comparison confirms the unique feature of our proposed thermoelectric skewness, as well as its special role of connection between the statistics of TDF and thermoelectric properties of materials. It is also found that the thermoelectric performance can be enhanced by increasing the asymmetry of TDF. Finally, it is also interesting to find that the thermoelectric transport properties based on typical quantum statistics (Fermi-Dirac distributions) can be well described by typical shape parameter (skewness) for classical statistics.
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Affiliation(s)
- Jin-Cheng Zheng
- Department of Physics, Xiamen University, Xiamen 361005, China
- Department of Physics and Department of New Energy Science and Engineering, Xiamen University Malaysia, Sepang 43900, Malaysia
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Liu YG, Ren GL, Chernatynskiy A, Zhao XF. The effect of interface angle on the thermal conductivity of Si/Ge superlattices. Phys Chem Chem Phys 2021; 23:23225-23232. [PMID: 34623359 DOI: 10.1039/d1cp03544d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Si/Ge superlattices (SLs) are good candidates for thermoelectric materials because of their remarkable thermal insulating performance compared with their bulk counterparts. In this paper, the non-equilibrium molecular dynamics (NEMD) simulation method was applied to investigate the thermal conductivity of Si/Ge SLs containing tilted interfaces. It was found that the thermal conductivity will be 4-5 times higher than that of other angles when the period length is 4-8 atomic layers and the interface angle is 45°. This phenomenon can be attributed to the smooth arrangement of the 45° interface which induces phonon coherent transport. Meanwhile, the thermal conductivity has not been improved due to the phonon localization although the phonons satisfy the coherent transport when the interface angle is 90°. Interestingly, the thermal conductivity is almost unchanged with the increasing interface angle when the period length is large enough which exceeds 20 atomic layers. The main reason for the unchanged thermal conductivity is due to the period length which is greater than the phonon coherence length inducing the phonon incoherent transport.
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Affiliation(s)
- Ying-Guang Liu
- Department of Power Engineering, School of Energy and Power Engineering, North China Electric Power University, Baoding 071003, China. .,Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology, North China Electric Power University, Baoding 071003, Hebei, China
| | - Guo-Liang Ren
- Department of Power Engineering, School of Energy and Power Engineering, North China Electric Power University, Baoding 071003, China. .,School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | | | - Xiao-Feng Zhao
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
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Tse J, Aziz A, Flitcroft J, Skelton JM, Gillie LJ, Parker SC, Cooke DJ, Molinari M. Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO 3 and La-Doped SrTiO 3 Materials: A Density Functional Theory Study. ACS Appl Mater Interfaces 2021; 13:41303-41314. [PMID: 34405998 PMCID: PMC8414480 DOI: 10.1021/acsami.1c10865] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/06/2021] [Indexed: 06/12/2023]
Abstract
We present a detailed theoretical investigation of the interaction of graphene with the SrO-terminated (001) surface of pristine and La-doped SrTiO3. The adsorption of graphene is thermodynamically favorable with interfacial adsorption energies of -0.08 and -0.32 J/m2 to pristine SrTiO3 and La-doped SrTiO3 surfaces, respectively. We find that graphene introduces C 2p states at the Fermi level, rendering the composite semimetallic, and thus the electrical properties are predicted to be highly sensitive to the amount and quality of the graphene. An investigation of the lattice dynamics predicts that graphene adsorption may lead to a 60-90% reduction in the thermal conductivity due to a reduction in the phonon group velocities, accounting for the reduced thermal conductivity of the composite materials observed experimentally. This effect is enhanced by La doping. We also find evidence that both La dopant ions and adsorbed graphene introduce low-frequency modes that may scatter heat-carrying acoustic phonons, and that, if present, these effects likely arise from stronger phonon-phonon interactions.
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Affiliation(s)
- Joshua Tse
- Department
of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
| | - Alex Aziz
- Department
of Chemistry, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
| | - Joseph
M. Flitcroft
- Department
of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
- Department
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Jonathan M. Skelton
- Department
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Lisa J. Gillie
- Department
of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
| | | | - David J. Cooke
- Department
of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
| | - Marco Molinari
- Department
of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.
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