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Synthesis and characterization of two- and three-dimensional nanolaminated carbides
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused towards the synthesis and characterization of novel nanolaminated materials in primarily bulk (powder) form. Of particular interest is magnetic materials, or laminates that can be used as precursor for two-dimensional (2D) materials. 2D materials typically display a large surface-to-volume ratio, and as such they are very promising for applications within energy storage and catalysis. A more recently discovered family of 2D transition metal carbides/nitrides, called MXenes, are currently attracting a lot of attention. MXenes are produced by selective etching of parent 3D nanolaminates, so called MAX phases, facilitating removal of selected atomic layers, and formation of 2D sheets.

In my work on new nanolaminates as precursors for 2D materials, I have synthesized (Mo2/3Sc1/3)2AlC and have studied its crystal structure. It was found that Mo and Sc are chemically ordered in the metal layers, with the in-plane ordering motivating the notation i-MAX for this new type of MAX phase alloy. By selective etching of Sc and Al, we thereafter produced a 2D materials with ordered vacancies, Mo1.33C, and studied the electrochemical properties. It was found that the material displayed a high capacitance, ~1200 F cm-3, which is 65% higher that the counterpart without vacancies, Mo2C.

I also synthesized a previously not known out-of-plane ordered Mo2ScAlC2 MAX phase. By selective etching of Al, we produced a 2D material, Mo2ScC2, which is correspondingly ordered in the out-of-plane direction. Another related laminated material was also discovered and synthesized, Sc2Al2C3, and its crystal structure was determined. The material is potentially useful for conversion into a 2D material. I have also shown that Sc2Al2C3 is an example of a series of materials with the same crystal structure, with Sc replaced by other metals.

Magnetic materials are used in many applications, such as for data storage devices. In particular, layered magnetic materials are of interest due to their anisotropic structure and potential formation of interesting magnetic characteristics. I have been synthesizing and characterizing magnetic nanolaminates, starting with the (V,Mn)3GaC2 MAX phase in the form of an epitaxial thin film. Analysis of the magnetic behavior showed a ferromagnetic response above room temperature I thereafter showed that our previously discovered family of i-MAX phases could be expanded with a subclass of ordered nanolaminates based on rare earth (RE) elements, of the general formula (Mo2/3RE1/3)2AlC , where RE=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. I studied their crystal structure by scanning transmission microscopy (STEM), X-ray diffraction (XRD), and neutron diffraction. We found that these phases can crystalize in three different structures, of space group C2/m, C2/c, and Cmcm, respectively. The magnetic behavior was studied and the magnetic structure of two materials could be determined. We suggest that the complex behavior identified is due to competing magnetic interaction and frustration.

I also synthesized another rare earth-based nanolaminate, Mo4Ce4Al7C3. The crystal structure was investigated by single crystal X-ray diffraction and STEM. Magnetization analysis reveal a ferromagnetic ground state below 10.5 K. X-ray absorption near-edge structure provide evidence that Ce is in a mixed-valence state. X-ray magnetic circular dichroism shows that only one of the two Ce sites are magnetic. 

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2020. , p. 44
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2058
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-163847DOI: 10.3384/diss.diva-163847ISBN: 9789179298791 (print)OAI: oai:DiVA.org:liu-163847DiVA, id: diva2:1395330
Public defence
2020-03-26, F-building, Campus Valla, Linköping, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationAvailable from: 2020-03-02 Created: 2020-02-21 Last updated: 2020-03-11Bibliographically approved
List of papers
1. Atomically Layered and Ordered Rare-Earth i-MAX Phases: A New Class of Magnetic Quaternary Compounds
Open this publication in new window or tab >>Atomically Layered and Ordered Rare-Earth i-MAX Phases: A New Class of Magnetic Quaternary Compounds
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 7, p. 2476-2485Article in journal (Refereed) Published
Abstract [en]

In 2017, we discovered quaternary i-MAX phases atomically layered solids, where M is an early transition metal, A is an A group element, and X is C-with a ((M2/3M1/32)-M-1)(2)AC chemistry, where the M-1 and M-2 atoms are in-plane ordered. Herein, we report the discovery of a class of magnetic i-MAX phases in which bilayers of a quasi-2D magnetic frustrated triangular lattice overlay a Mo honeycomb arrangement and an Al Kagome lattice. The chemistry of this family is (Mo2/3RE1/3)(2)AlC, and the rare-earth, RE, elements are Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The magnetic properties were characterized and found to display a plethora of ground states, resulting from an interplay of competing magnetic interactions in the presence of magnetocrystalline anisotropy.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-157225 (URN)10.1021/acs.chemmater.8b05298 (DOI)000464477100029 ()
Note

Funding Agencies|Knut and Alice Wallenberg (KAW) Foundation [KAW 2015.0043]; Swedish Research Council [642-2013-8020, 2015-00607, 621-2014-4890]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; DFG [SA 3095/2-1]; IAEC Pazy Foundation Grant; NSF [DMR-1740795]

Available from: 2019-06-13 Created: 2019-06-13 Last updated: 2020-03-26
2. Rare-earth (RE) nanolaminates Mo4RE4Al7C3 featuring ferromagnetism and mixed-valence states
Open this publication in new window or tab >>Rare-earth (RE) nanolaminates Mo4RE4Al7C3 featuring ferromagnetism and mixed-valence states
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2018 (English)In: PHYSICAL REVIEW MATERIALS, ISSN 2475-9953, Vol. 2, no 11, article id 114401Article in journal (Refereed) Published
Abstract [en]

Rare-earth-based (RE) nanolaminates have attracted attention recently because of their complicated magnetism and their potential as precursors for strongly correlated two-dimensional materials. In this work, we synthesized a class of nanolaminates with a Mo4RE4Al7C3 chemistry, where RE = Ce or Pr. Powder samples of both phases were characterized with respect to structure and composition. Single crystals of Mo4Ce4Al7C3 were used for magnetization measurements. The crystal structure was investigated by means of x-ray diffraction and scanning transmission electron microscopy. Magnetization analysis reveals a ferromagnetic ground state with a Curie temperature of similar to 10.5 K. X-ray absorption near-edge structure provides experimental evidence that Ce is in a mixed-valence state. X-ray magnetic circular dichroism shows that only the Ce atoms with 4f(1) configuration occupying one of the two possible sites are ferromagnetically coupled, with a saturation moment of similar to 1.2 mu(B) per atom. We thus classify Mo4Ce4Al7C3 as a ferromagnetic, mixed-valence compound.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-153172 (URN)10.1103/PhysRevMaterials.2.114401 (DOI)000450570100003 ()
Note

Funding Agencies|Knut and Alice Wallenberg (KAW) Foundation through a Fellowship [0358, KAW 2015.0043]; Swedish Research council [642-2013-8020]; Flag-ERA JTC; chair of excellence program of the Nanosciences Foundation (Universite Grenoble-Alpes Foundation); Federation Wallonie-Bruxelles through the Action de Recherche Concertee "3D nanoarchitecturing of 2D crystals" [16/21-077]; European Union [696656]; Belgium FNRS (Flag-ERA) [R. 50.01.18.F]; Fonds de la Recherche Scientifique de Belgique (F.R.S. -FNRS) [2.5020.11]; Linkoping Ultra Electron Microscopy Laboratory

Available from: 2018-12-01 Created: 2018-12-01 Last updated: 2020-02-21
3. Two-dimensional Mo1.33C MXene with divacancy ordering prepared from parent 3D laminate with in-plane chemical ordering
Open this publication in new window or tab >>Two-dimensional Mo1.33C MXene with divacancy ordering prepared from parent 3D laminate with in-plane chemical ordering
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2017 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 14949Article in journal (Refereed) Published
Abstract [en]

The exploration of two-dimensional solids is an active area of materials discovery. Research in this area has given us structures spanning graphene to dichalcogenides, and more recently 2D transition metal carbides (MXenes). One of the challenges now is to master ordering within the atomic sheets. Herein, we present a top-down, high-yield, facile route for the controlled introduction of ordered divacancies in MXenes. By designing a parent 3D atomic laminate, (Mo2/3Sc1/3)(2)AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, we show evidence for 2D Mo1.33C sheets with ordered metal divacancies and high electrical conductivities. At similar to 1,100 F cm(-3), this 2D material exhibits a 65% higher volumetric capacitance than its counterpart, Mo2C, with no vacancies, and one of the highest volumetric capacitance values ever reported, to the best of our knowledge. This structural design on the atomic scale may alter and expand the concept of property-tailoring of 2D materials.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-137387 (URN)10.1038/ncomms14949 (DOI)000400065800001 ()28440271 (PubMedID)
Note

Funding Agencies|Swedish Foundation for Strategic Research (SSF) through Synergy Grant FUNCASE; Knut and Alice Wallenberg (KAW) Foundation [KAW 2015.0043]; Swedish Research council [621-2012-4359, 622-2008-405, 621-2012-4425, 642-2013-8020]

Available from: 2017-05-18 Created: 2017-05-18 Last updated: 2020-02-21
4. Thin film synthesis and characterization of a chemically ordered magnetic nanolaminate (V,Mn)(3)GaC2
Open this publication in new window or tab >>Thin film synthesis and characterization of a chemically ordered magnetic nanolaminate (V,Mn)(3)GaC2
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2016 (English)In: APL MATERIALS, ISSN 2166-532X, Vol. 4, no 8, article id 086109Article in journal (Refereed) Published
Abstract [en]

We report on synthesis and characterization of a new magnetic nanolaminate (V,Mn)(3)GaC2, which is the first magnetic MAX phase of a 312 stoichiometry. Atomically resolved energy dispersive X-ray mapping of epitaxial thin films reveals a tendency of alternate chemical ordering between V and Mn, with atomic layers composed of primarily one element only. Magnetometry measurements reveal a ferromagnetic response between 50 K and 300 K, with indication of a magnetic ordering temperature well above room temperature. (C) 2016 Author(s).

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-132079 (URN)10.1063/1.4961502 (DOI)000383910000010 ()
Note

Funding Agencies|Swedish Research Council (VR) [621-2012-4425, 642-2013-8020]; Knut and Alice Wallenberg (KAW) Foundation; Swedish Foundation for Strategic Research (SSF) through the synergy grant FUNCASE; DFG [SA 3095/2-1]

Available from: 2016-10-18 Created: 2016-10-17 Last updated: 2020-02-21
5. Theoretical stability and materials synthesis of a chemically ordered MAX phase, Mo2ScAlC2, and its two-dimensional derivate Mo2ScC2 MXene
Open this publication in new window or tab >>Theoretical stability and materials synthesis of a chemically ordered MAX phase, Mo2ScAlC2, and its two-dimensional derivate Mo2ScC2 MXene
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2017 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 125, p. 476-480Article in journal (Refereed) Published
Abstract [en]

We present theoretical prediction and experimental evidence of a new MAX phase alloy, Mo2ScAlC2, with out-of-plane chemical order. Evaluation of phase stability was performed by ab initio calculations based on Density Functional Theory, suggesting that chemical order in the alloy promotes a stable phase, with a formation enthalpy of -24 meV/atom, as opposed to the predicted unstable Mo3AlC2 and Sc3AlC2. Bulk synthesis of Mo2ScAlC2 is achieved by mixing elemental powders of Mo, Sc, Al and graphite which are heated to 1700 degrees C. High resolution transmission electron microscopy reveals a chemically ordered structure consistent with theoretical predictions with one Sc layer sandwiched between two Mo-C layers. The two-dimensional derivative, the MXene, is produced by selective etching of the Al-layers in hydrofluoric acid, resulting in the corresponding chemically ordered Mo2ScC2, i.e. the first Sc-containing MXene. The here presented results expands the attainable range of MXene compositions and widens the prospects for property tuning. (C)2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2017
Keywords
Laminated structure; Out-of-plane chemical order; MAX phase; 2D material; MXene; DFT calculations
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-136312 (URN)10.1016/j.actamat.2016.12.008 (DOI)000394201500047 ()
Note

Funding Agencies|Swedish Research Council (VR) [621-2012-4425, 642-2013-8020]; Knut and Alice Wallenberg (KAW) Foundation; Swedish Foundation for Strategic Research (SSF) through the synergy grant FUNCASE; KAW Foundation

Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2020-02-21
6. Single crystal growth and structural characterization of thetheoretically predicted nanolaminate M2Al2C3 where M=Sc and Er
Open this publication in new window or tab >>Single crystal growth and structural characterization of thetheoretically predicted nanolaminate M2Al2C3 where M=Sc and Er
(English)In: Article in journal, Letter (Refereed) Submitted
Abstract [en]

Nanolaminated materials including magnetic elements are of interest for commonly observed non-trivial magnetic characteristics and as potential precursors for 2D materials. Here, we explore the previously unknown layered phase M2Al2C3 where M = Sc and Er. Sc2Al2C3 was synthesized as single crystals of ~mm2 size, and its structure was determined by single crystal X-ray diffraction and scanning transmission electron microscopy. Evaluation of phase stability and possible vacancy formation based on first principles calculations confirm the attained phase, and suggest full occupancy on both the Al and C sites. Potential realization of the hypothetical phase Y2Al2C3 is also proposed. Furthermore, we also demonstrate that Er2Al2C3 can be synthesized in powder form, providing experimental evidence for stoichiometries based on rare earth (RE) elements, which in turn suggests possible incorporation of other lanthanides.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-163846 (URN)
Available from: 2020-02-21 Created: 2020-02-21 Last updated: 2020-02-21

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