Abstract
Misfit layered compounds (MLCs) have been studied in the literature for the last 40 years. They are generally made of an alternating sequence of two monolayers, a distorted rocksalt structure, and a hexagonal layered compound. In a typical MLC, the c-axis is common to the two monolayers and so is one of the axes in the layer plan. However, the two compounds are non-commensurate along at least one axis, and the ratio between the two axes is an irrational number making the MLC a non-stoichiometric compound. The two main families of MLC are those based on metal dichalcogenides and CoO2 as the hexagonal layered compound. Traditionally, ternary MLCs were prepared and studied, but some quaternary and multinary MLC minerals have been known for many years. Over the last few years, interest in MLCs with four and even larger number of atoms has grown. Doping or alloying of a ternary MLC permits precise control of the charge carrier density and hence the electrical, thermoelectric, catalytic, and optical properties of such compounds. In this short review, some of these developments will be discussed with the main emphasis put on quaternary MLC nanotubes belonging to the chalcogenide series. The synthesis, structural characterization, and some of their properties are considered. Some recent developments in quaternary cobaltite MLCs and recent studies on exfoliated MLCs are discussed as well.
Highlights
Misfit layered compounds (MLCs) are (2D) non-stoichiometric materials comprising two interpenetrating sublattices differing in at least one of their lattice parameters [1,2]
Chemical vapor transport (CVT) and physical vapor transport (PVT) were found to be successful strategies for the synthesis of a series of quaternary MLC nanotubes, the yield of the nanotubes varied from one compound to the other and was far below unity
In order to shed light on the stability of such quaternary MLCs, for the following reaction was calculated through density functional theory (DFT): the energy difference for the following reaction was calculated through density functional theory (DFT): (LaS)1+y TaS2 + (La0.95 Ln0.05 )S → (La0.95 Ln0.05 )1+y STaS2 + LaS, y = 0.11 (LaS)1+yTaS2 + (La0.95Ln0.05)S → (La0.95Ln0.05)1+ySTaS2 + LaS, y = 0.11
Summary
Misfit layered compounds (MLCs) are (2D) non-stoichiometric materials comprising two interpenetrating sublattices differing in at least one of their lattice parameters [1,2]. These layers are made of a stacking of a distorted rocksalt slab attached to a layered material with hexagonal structure. The most studied structures are misfit materials based on either metal dichalcogenides or the layered cobaltites, which will only briefly be mentioned here.
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