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	Author	Meng, X.; Chen, S.; Peng, H.; Bai, H.; Zhang, S.; Su, X.; Tan, G.; Van Tendeloo, G.; Sun, Z.; Zhang, Q.; Tang, X.; Wu, J.
	Title	Ferroelectric engineering : enhanced thermoelectric performance by local structural heterogeneity			Type	A1 Journal article
	Year	2022	Publication	Science China : materials	Abbreviated Journal	Sci China Mater
	Volume		Issue		Pages
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Although traditional ferroelectric materials are usually dielectric and nonconductive, GeTe is a typical ferroelectric semiconductor, possessing both ferroelectric and semiconducting properties. GeTe is also a widely studied thermoelectric material, whose performance has been optimized by doping with various elements. However, the impact of the ferroelectric domains on the thermoelectric properties remains unclear due to the difficulty to directly observe the ferroelectric domains and their evolutions under actual working conditions where the material is exposed to high temperatures and electric currents. Herein, based on in-situ investigations of the ferroelectric domains and domain walls in both pure and Sb-doped GeTe crystals, we have been able to analyze the dynamic evolution of the ferroelectric domains and domain walls, exposed to an electric field and temperature. Local structural heterogeneities and nano-sized ferroelectric domains are generated due to the interplay of the Sb3+ dopant and the Ge-vacancies, leading to the increased number of charged domain walls and a much improved thermoelectric performance. This work reveals the fundamental mechanism of ferroelectric thermoelectrics and provides insights into the decoupling of previously interdependent properties such as thermo-power and electrical conductivity.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000749973500001	Publication Date	2022-02-02
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2095-8226; 2199-4501	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	8.1	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 8.1
	Call Number	UA @ admin @ c:irua:186429			Serial	6959
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	Author	Sun, C.; Liao, X.; Peng, H.; Zhang, C.; Van Tendeloo, G.; Zhao, Y.; Wu, J.
	Title	Interfacial gliding-driven lattice oxygen release in layered cathodes			Type	A1 Journal article
	Year	2022	Publication	Cell reports physical science	Abbreviated Journal
	Volume	3	Issue	1	Pages
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	The oxygen release of layered cathodes causes many battery failures, but the underlying mechanism in an actual working cathode is still elusive as it involves secondary agglomerates that introduce complicated boundary structures. Here, we report a general structure instability on the mismatch boundaries driven by interfacial gliding-it introduces a shear stress causing a distortion of the metal-oxygen octahedra framework that reduces its kinetic stability. The migration of cations and diffusion of oxygen vacancies continue to degrade the whole particle from the boundary to the interior, followed by the formation of nano-sized cracks on the fast-degrading interfaces. This work reveals a robust chemical and mechanical interplay on the oxygen release inherent to the intergranular boundaries of layered cathodes. It also suggests that radially patterned columnar grains with low-angle planar boundaries would be an efficient approach to mitigate the boundary oxygen release.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000745659500012	Publication Date	2021-12-20
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN		ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor		Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: NA
	Call Number	UA @ admin @ c:irua:186420			Serial	6961
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	Author	Liang, Q.; Yang, D.; Xia, F.; Bai, H.; Peng, H.; Yu, R.; Yan, Y.; He, D.; Cao, S.; Van Tendeloo, G.; Li, G.; Zhang, Q.; Tang, X.; Wu, J.
	Title	Phase-transformation-induced giant deformation in thermoelectric Ag₂Se semiconductor			Type	A1 Journal article
	Year	2021	Publication	Advanced Functional Materials	Abbreviated Journal	Adv Funct Mater
	Volume		Issue		Pages	2106938
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	In most semiconducting metal chalcogenides, a large deformation is usually accompanied by a phase transformation, while the deformation mechanism remains largely unexplored. Herein, a phase-transformation-induced deformation in Ag2Se is investigated by in situ transmission electron microscopy, and a new ordered high-temperature phase (named as alpha '-Ag2Se) is identified. The Se-Se bonds are folded when the Ag+-ion vacancies are ordered and become stretched when these vacancies are disordered. Such a stretch/fold of the Se-Se bonds enables a fast and large deformation occurring during the phase transition. Meanwhile, the different Se-Se bonding states in alpha-, alpha '-, beta-Ag2Se phases lead to the formation of a large number of nanoslabs and the high concentration of dislocations at the interface, which flexibly accommodate the strain caused by the phase transformation. This study reveals the atomic mechanism of the deformation in Ag2Se inorganic semiconductors during the phase transition, which also provides inspiration for understanding the phase transition process in other functional materials.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000695142800001	Publication Date	2021-09-13
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1616-301x	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	12.124	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 12.124
	Call Number	UA @ admin @ c:irua:181527			Serial	6879
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	Author	Peng, X.; Peng, H.; Zhao, K.; Zhang, Y.; Xia, F.; Lyu, J.; Van Tendeloo, G.; Sun, C.; Wu, J.
	Title	Direct visualization of atomic-scale heterogeneous structure dynamics in MnO₂ nanowires			Type	A1 Journal article
	Year	2021	Publication	Acs Applied Materials & Interfaces	Abbreviated Journal	Acs Appl Mater Inter
	Volume	13	Issue	28	Pages	33644-33651
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	Manganese oxides are attracting great interest owing to their rich polymorphism and multiple valent states, which give rise to a wide range of applications in catalysis, capacitors, ion batteries, and so forth. Most of their functionalities are connected to transitions among the various polymorphisms and Mn valences. However, their atomic-scale dynamics is still a great challenge. Herein, we discovered a strong heterogeneity in the crystalline structure and defects, as well as in the Mn valence state. The transitions are studied by in situ transmission electron microscopy (TEM), and they involve a complex ordering of [MnO6] octahedra as the basic building tunnels. MnO2 nanowires synthesized using solution-based hydrothermal methods usually exhibit a large number of multiple polymorphism impurities with different tunnel sizes. Upon heating, MnO2 nanowires undergo a series of stoichiometric polymorphism changes, followed by oxygen release toward an oxygen-deficient spinel and rock-salt phase. The impurity polymorphism exhibits an abnormally high stability with interesting small-large-small tunnel size transition, which is attributed to a preferential stabilizer (K+) concentration, as well as a strong competition of kinetics and thermodynamics. Our results unveil the complicated intergrowth of polymorphism impurities in MnO2, which provide insights into the heterogeneous kinetics, thermodynamics, and transport properties of the tunnel-based building blocks.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000677540900101	Publication Date	2021-07-08
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1944-8244	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	7.504	Times cited		Open Access	Not_Open_Access
	Notes				Approved	Most recent IF: 7.504
	Call Number	UA @ admin @ c:irua:180450			Serial	6861
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	Author	Liu, F.; Meng, J.; Xia, F.; Liu, Z.; Peng, H.; Sun, C.; Xu, L.; Van Tendeloo, G.; Mai, L.; Wu, J.
	Title	Origin of the extra capacity in nitrogen-doped porous carbon nanofibers for high-performance potassium ion batteries			Type	A1 Journal article
	Year	2020	Publication	Journal Of Materials Chemistry A	Abbreviated Journal	J Mater Chem A
	Volume	8	Issue	35	Pages	18079-18086
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	While graphite has limited capacity as an anode material for potassium-ion batteries, nitrogen-doped carbon materials are more promising as extra capacity can usually be produced. However, the mechanism behind the origin of the extra capacity remains largely unclear. Here, the potassium storage mechanisms have been systematically studied in freestanding and porous N-doped carbon nanofibers with an additional similar to 100 mA h g(-1)discharge capacity at 0.1 A g(-1). The extra capacity is generated in the whole voltage window range from 0.01 to 2 V, which corresponds to both surface/interface K-ion absorptions due to the pyridinic N and pyrrolic N induced atomic vacancies and layer-by-layer intercalation due to the effects of graphitic N. As revealed by transmission electron microscopy, the N-doped samples have a clear and enhanced K-intercalation reaction. Theoretical calculations confirmed that the micropores with pyridinic N and pyrrolic N provide extra sites to form bonds with K, resulting in the extra capacity at high voltage. The chemical absorption of K-ions occurring inside the defective graphitic layer will prompt fast diffusion of K-ions and full realization of the intercalation capacity at low voltage. The approach of preparing N-doped carbon-based materials and the mechanism revealed by this work provide directions for the development of advanced materials for efficient energy storage.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000569873400015	Publication Date	2020-08-03
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2050-7488; 2050-7496	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	11.9	Times cited	2	Open Access	OpenAccess
	Notes	; F. Liu and J. S. Meng contributed equally to this work. This work was supported by the National Natural Science Foundation of China (51832004 and 51521001), the National Key Research and Development Program of China (2016YFA0202603), and the Natural Science Foundation of Hubei Province (2019CFA001). The S/TEM work was performed at the Nanostructure Research Center (NRC), which is supported by the Fundamental Research Funds for the Central Universities (WUT: 2019III012GX, 2020III002GX), the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, and the State Key Laboratory of Silicate Materials for Architectures (all of the laboratories are at Wuhan University of Technology). ;			Approved	Most recent IF: 11.9; 2020 IF: 8.867
	Call Number	UA @ admin @ c:irua:172741			Serial	6573
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	Author	Sun, C.; Liao, X.; Xia, F.; Zhao, Y.; Zhang, L.; Mu, S.; Shi, S.; Li, Y.; Peng, H.; Van Tendeloo, G.; Zhao, K.; Wu, J.
	Title	High-voltage cycling induced thermal vulnerability in LiCoO₂ cathode : cation loss and oxygen release driven by oxygen vacancy migration			Type	A1 Journal article
	Year	2020	Publication	Acs Nano	Abbreviated Journal	Acs Nano
	Volume	14	Issue	5	Pages	6181-6190
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	The release of the lattice oxygen due to the thermal degradation of layered lithium transition metal oxides is one of the major safety concerns in Li-ion batteries. The oxygen release is generally attributed to the phase transitions from the layered structure to spinel and rocksalt structures that contain less lattice oxygen. Here, a different degradation pathway in LiCoO2 is found, through oxygen vacancy facilitated cation migration and reduction. This process leaves undercoordinated oxygen that gives rise to oxygen release while the structure integrity of the defect-free region is mostly preserved. This oxygen release mechanism can be called surface degradation due to the kinetic control of the cation migration but has a slow surface to bulk propagation with continuous loss of the surface cation ions. It is also strongly correlated with the high-voltage cycling defects that end up with a significant local oxygen release at low temperatures. This work unveils the thermal vulnerability of high-voltage Li-ion batteries and the critical role of the surface fraction as a general mitigating approach.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000537682300101	Publication Date	2020-04-17
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1936-0851	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	17.1	Times cited	8	Open Access	Not_Open_Access
	Notes	; C.S., X.L., and F.X. contributed equally to this work. This work was supported by the National Natural Science Foundation of China (21905169). The S/TEM work was performed at the Nanostructure Research Center (NRC), which is supported by the Fundamental Research Funds for the Central Universities (WUT: 2019III012GX), the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, and the State Key Laboratory of Silicate Materials for Architectures (all of the laboratories are at Wuhan University of Technology). ;			Approved	Most recent IF: 17.1; 2020 IF: 13.942
	Call Number	UA @ admin @ c:irua:170246			Serial	6537
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	Author	Wu, S.; Luo, X.; Turner, S.; Peng, H.; Lin, W.; Ding, J.; David, A.; Wang, B.; Van Tendeloo, G.; Wang, J.; Wu, T.;
	Title	Nonvolatile resistive switching in Pt/LaAlO₃/SrTiO₃ heterostructures			Type	A1 Journal article
	Year	2013	Publication	Physical review X	Abbreviated Journal	Phys Rev X
	Volume	3	Issue	4	Pages	041027-14
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in Pt/LaAlO3/SrTiO3 heterostructures, where the conducting layer near the LaAlO3/SrTiO3 interface serves as the unconventional bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the LaAlO3/SrTiO3 interface and the creation of defect-induced gap states within the ultrathin LaAlO3 layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	College Park, Md	Editor
	Language		Wos	000328862400001	Publication Date	2013-12-17
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	2160-3308;	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	12.789	Times cited	77	Open Access
	Notes	FWO;FP7;IFOX; Countatoms; Hercules			Approved	Most recent IF: 12.789; 2013 IF: 8.463
	Call Number	UA @ lucian @ c:irua:112524			Serial	2365
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