Phasenuntersuchungen im System 2 Ha–TaS2–2Hc–MoS2 / Investigations on Phases in the System 2 Ha-TaS2-2Hc-MoS2

Remmert, P.; Fischer, Edmund; Hummel, H.-U.

doi:10.1515/znb-1994-0904

Cited by 3 publications

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“…35 These results corroborate that the prepared dichalcogenides are present in a compact hexagonal structure, with the Ta and Mo metals in a trigonal prismatic coordination (3R polytype). As indicated above, the stabilization of such structural type is indicative of a metallic character, a result which was corroborated by the conductivity measurements performed at different temperatures (vide infra).…”

Section: Resultssupporting

confidence: 81%

“…418 of precursors at 900 ºC. It was noticed that the addition of NH 4 Cl was not necessary as preconized by Remmert et al 35 in the first report on the preparation of these ternary sulfides. FE-SEM images of the resulting solids show the presence of micrometric crystals of hexagonal shape (Figure 1) with compositions that are in the range of the expected values, as deduced from EDX semiquantitative analysis.…”

Section: Ta X Mo 1-x S 2 Dichalcogenidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Theoretically, the conduction band of TaS 2 (d z 2 ) can be filled by electrons from molybdenum as the Mo/Ta ratio increases in the mixed dichalcogenides. Ternary Ta-Mo sulfides were first described by Remmert et al,35,36 who reported their structural features with preliminary information on their conducting behavior and the possibility to intercalate compounds such as pyridine.The aim of this work is to enhance the knowledge of these ternary compounds by investigating the electrical and electrochemical behaviors of various Ta x Mo 1-x S 2 phases, as well as of the derivatives resulting from their intercalation by different species: Li + , pyridine and PEO. It should be noticed that Ta x Mo 1-x S 2 mixed chalcogenides can combine characteristics from both the semiconductor MoS 2 and the metallic TaS 2 , which theoretically can be further modified by intercalation reactions.…”

mentioning

confidence: 99%

“…It was noticed that the addition of NH 4 Cl was not necessary as preconized by Remmert et al 35 in the first report on the preparation of these ternary sulfides. FE-SEM images of the resulting solids show the presence of micrometric crystals of hexagonal shape (Figure 1) with compositions that are in the range of the expected values, as deduced from EDX semiquantitative analysis.This work employed ternary phases in the 0.50 < x < 1.00 composition range with x = 0.55, 0.75 and 0.90 because, according to Remmert et al,35 for compositions with x below ca. 0.50, a mixture of several phases of variable composition can be formed together with segregated MoS 2 crystals.…”

mentioning

confidence: 99%

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Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Lara¹,

Ruiz²,

Manrı́quez³

et al. 2012

J. Braz. Chem. Soc.

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Este trabalho relata um estudo sistemático do comportamento estrutural e elétrico de três fases ternárias do sistema Ta x Mo 1-x S 2 (x = 0,55, 0,75 e 0,90) e de seus compostos de intercalação resultantes das inserções química e eletroquímica de lítio, assim como das intercalações de piridina e poli(óxido de etileno). As três fases foram preparadas pela reação direta de seus elementos constituintes, sem qualquer outro aditivo, a 900 o C em atmosfera inerte. Os compostos resultantes foram caracterizados por meio de difratometria de raios X de pó (XRD), análises termogravimétrica e térmica diferencial (TGA/DTA), fluorescência de raios X por dispersão de energia (EDX) e microscopia eletrônica de varredura com emissão de campo (FE-SEM). A condutividade elétrica dos diferentes compostos preparados foi medida no intervalo de temperatura 1,5-300 K utilizando o método convencional de sonda de quatro pontas van der Pauw na presença de um campo magnético de 9 T para verificar a ocorrência do fenômeno de magnetoresistividade.This work reports a systematic study of the structural and electrical behavior of three ternary phases of the Ta x Mo 1-x S 2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 ºC in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena. Keywords: chalcogenides, intercalation, pyridine, PEO, conductivity IntroductionThe renewed interest to study layered solids is originated from the observation of unusual physical properties associated with anisotropy phenomena in such type of low-dimensional materials. Another important reason why 2D solids are investigated is their ability to intercalate a large variety of compounds. [1][2][3][4][5][6][7][8][9] In this context, physical properties such as electrical conductivity and electrochemical behavior of layered solids can be deliberately modified by intercalation of organic species. [2][3][4]10,11 Among different 2D solids, the study of layered transition-metal dichalcogenides (LTMDs) has become the subject of an active field of research in solid state physics and chemistry during the last decades. 1,12,13 One of the most salient physical properties of these materials is their electrical conductivity (and superconductivity) behavior, which is related to phase transitions usually driven by charge density wave mechanisms...

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Section: Resultssupporting

confidence: 81%

Section: Ta X Mo 1-x S 2 Dichalcogenidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Lara¹,

Ruiz²,

Manrı́quez³

et al. 2012

J. Braz. Chem. Soc.

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Transition Metal–MoS2 Reactions: Review and Thermodynamic Predictions

Domask

Gurunathan

Mohney

2015

Journal of Elec Materi

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Molybdenum disulfide is a layered transition-metal dichalcogenide semiconductor that is attracting renewed attention for its potential use in future nanoscale electronics, optoelectronics, catalysis, tribology, and other fields. In all of these cases, the interaction between MoS 2 and various transition metals is very important. In this work we survey the thermodynamics of the metal-Mo-S systems and the anticipated reaction products from transition metals and MoS 2 . We examined over 200 references on the reactions between transitions metals (M) and MoS 2 , compiled thermodynamic data, and used the thermodynamic data to predict M-Mo-S ternary phase diagrams for systems without experimentally determined diagrams. Where possible, experimental literature on the interactions between metals and MoS 2 was used to corroborate our predicted diagrams and stable reaction products. Both the previously reported and newly predicted M-Mo-S phase diagrams fall into three categories. In the first category, the metal is in thermodynamic equilibrium with MoS 2 . In another, there is a driving force for the metal to reduce MoS 2 , with tie lines to sulfides of the contact metal dominating the phase diagram. In a final category, there is a very stable solid solution or ternary phase that dominates the phase diagram. Better understanding of the phase equilibria in the M-Mo-S systems will aid research on the use of MoS 2 in a variety of fields.

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Dissulfeto de molibdênio, um material multifuncional e surpreendente

Wypych

2002

Quím. Nova

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Recebido em 6/10/00; aceito em 4/4/01 MOLYBDENUM DISULFIDE, A MULTIFUNCTIONAL AND REMARKABLE MATERIAL. The aim of this work is to review the chemical and physical properties of layered molybdenum disulfide. The three polymorphic/polytypic modifications of the compound were found, the polytypes 2H (molybdenite) and 3R are semiconductors while the polymorph 1T is an electronic conductor. 2H-MoS 2 has several important industrial applications as hydrotreatment catalysts, energy storage devices, solar cells, solid lubricants, among others. When intercalated, the 2H phase changes to a distorted 1T phase, producing unstable intercalation compounds that can be exfoliated in solution, producing single layers and consequently nanocomposites. The direct synthesis of the 1T phase produces stable intercalation compounds. Recently molybdenum disulfide was prepared as nanotubes and fulerenelike structures that bring new insights in the investigation of this important material.Keywords: molybdenum disulfide; intercalation; layered materials. INTRODUÇÃOO dissulfeto de molibdênio pertence a uma classe de materiais conhecidos como compostos lamelares e ocorre em três modificações polimórficas/politípicas 1,2 . A fase mais comum (2H) ocorre na natureza na forma de molibdenita. Nas modificações 2H e 3R, áto-mos de molibdênio estão ligados covalentemente à átomos de enxofre numa geometria trigonal prismática regular (Figura 1). Os prismas trigonais estão ligados entre si pelas arestas, produzindo unidades bidimensionais conhecidas como lamelas. Essas lamelas que, estão conectadas por forças fracas do tipo Van der Waals, podem se ordenar de maneira diferente originando os dois politipos. Na fase 1T a forma ondulada se deve à distorção da esfera de coordenação octaédrica do centro metálico 2 . A forma do politipo 1T não distorcida está representada na Figura 1. Figura 1. Representação esquemática das estrutura das fases 2H, 3R e 1T (não distorcida), do dissulfeto de molibdênio.As propriedades dos politipos são diferentes. A fase 1T é condutora 2 enquanto que as fases 2H e 3R são diamagnéticas e semicondutoras 3. Além das três formas conhecidas de hábito cristalino, o dissulfeto de molibdênio se apresenta na forma amorfa 4,5 , como nanotubos 6,7 e esferas de dimensões nanoscópicas 7,8 semelhantes as estruturas dos fulerenos.As aplicações do dissulfeto de molibdênio vão desde baterias no estado sólido que utilizam meio não aquoso e íons lítio intercaláveis [9][10][11] , células solares 12 , como lubrificantes sólidos 13 , catalisadores [14][15][16][17][18] , onde desempenha um papel de importância fundamental, além de outras.Um dos processos de síntese do dissulfeto de molibdênio nas fases polimórficas 2H e 3R é a reação térmica direta entre o molibdênio metálico e enxofre elementar em ampolas de quartzo. Quando cristais grandes forem necessários utiliza-se o método de transporte de vapor químico com um halogeneto como o iodo como agente transportante 19 (Eq.1).Mo + 2 S ® MoS 2 + 2 I 2 « MoI 4 + S 2Nesse procedimento, quantidades estequ...

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Phasenuntersuchungen im System 2 Ha–TaS₂–2Hc–MoS₂ / Investigations on Phases in the System 2 Ha-TaS₂-2Hc-MoS₂

Cited by 3 publications

References 0 publications

Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Transition Metal–MoS2 Reactions: Review and Thermodynamic Predictions

Dissulfeto de molibdênio, um material multifuncional e surpreendente

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