Transition metal oxides – Thermoelectric properties
TL;DR: Transition metal oxides (TMOs) are a fascinating class of materials due to their wide ranging electronic, chemical and mechanical properties Additionally, they are gaining increasing attention for their thermoelectric (TE) properties due to tunable electronic and phonon transport properties and well established synthesis techniques as mentioned in this paper.
About: This article is published in Progress in Materials Science.The article was published on 2013-10-01 and is currently open access. It has received 306 citations till now. The article focuses on the topics: Thermoelectric materials & Thermoelectric effect.
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TL;DR: This article reviews this emerging class of 2D elemental materials - silicene, germanene, stanene, and phosphorene--with emphasis on fundamental properties and synthesis techniques and the viability of such elemental 2D materials is highlighted.
Abstract: The fascinating electronic and optoelectronic properties of free-standing graphene has led to the exploration of alternative two-dimensional materials that can be easily integrated with current generation of electronic technologies. In contrast to 2D oxide and dichalcogenides, elemental 2D analogues of graphene, which include monolayer silicon (silicene), are fast emerging as promising alternatives, with predictions of high degree of integration with existing technologies. This article reviews this emerging class of 2D elemental materials - silicene, germanene, stanene, and phosphorene--with emphasis on fundamental properties and synthesis techniques. The need for further investigations to establish controlled synthesis techniques and the viability of such elemental 2D materials is highlighted. Future prospects harnessing the ability to manipulate the electronic structure of these materials for nano- and opto-electronic applications are identified.
748 citations
TL;DR: The properties and applications of molybdenum oxides are reviewed in depth, while an insightful outlook into future prospective applications for moly bdenum oxide is presented.
Abstract: The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides.
465 citations
TL;DR: In this paper, a review of 2D materials is presented, along with their advantages and disadvantages, and some effective device-fabrication approaches, such as heterostructure approaches, are applied to further enhance the properties of two-dimensional materials; their novel device applications and opportunities are also presented.
Abstract: The technological evolution has been progressing for centuries and will possibly increase at a higher rate in the 21st century. Currently, in this age of nanotechnology, the discovery of more economical and sustainable novel materials has considerably increased. The abundance of two-dimensional (2D) materials has endowed them with a broad material platform in technical studies and in the expansion of nano- and atomic-level applications. The innovation of graphene has motivated considerable attention to the study of other novel 2D materials, known as modern day “alchemy”, by which scientists are trying to convert most possible periodic table elements into 2D material structures and forms. 2D material devices with high quality and good optical encoder performance have a multitude of industrial applications. However, their stability and large size restrict their applications, but these problems can be overcome by functionalization and substrate-based formation of 2D materials. Therefore, via this review, first, basic attributes of 2D materials are described, and the mechanisms to further enhance their properties are also summarized. Second, the applications of 2D materials are discussed, along with their advantages and disadvantages. Finally, some effective device-fabrication approaches, such as heterostructure approaches, are applied to further enhance the properties of 2D materials; their novel device applications and opportunities are also presented. This updated review may provide new avenues for 2D material synthesis and development of more efficient devices compared to conventional devices in different fields.
419 citations
TL;DR: The present contribution critically reviews the development and role of mesoporosity in a wide range of technologies, as this provides for critical improvements in accessibility, the dispersion of the active phase and a higher surface area.
Abstract: Alternative energy technologies are greatly hindered by significant limitations in materials science. From low activity to poor stability, and from mineral scarcity to high cost, the current materials are not able to cope with the significant challenges of clean energy technologies. However, recent advances in the preparation of nanomaterials, porous solids, and nanostructured solids are providing hope in the race for a better, cleaner energy production. The present contribution critically reviews the development and role of mesoporosity in a wide range of technologies, as this provides for critical improvements in accessibility, the dispersion of the active phase and a higher surface area. Relevant examples of the development of mesoporosity by a wide range of techniques are provided, including the preparation of hierarchical structures with pore systems in different scale ranges. Mesoporosity plays a significant role in catalysis, especially in the most challenging processes where bulky molecules, like those obtained from biomass or highly unreactive species, such as CO2 should be transformed into most valuable products. Furthermore, mesoporous materials also play a significant role as electrodes in fuel and solar cells and in thermoelectric devices, technologies which are benefiting from improved accessibility and a better dispersion of materials with controlled porosity.
409 citations
TL;DR: A comprehensive overview of 2D and layered transition metal oxides can be found in this paper, where the fundamentals and applications of planar TMOs are discussed and future prospects and pathways to new developments are presented.
378 citations
References
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TL;DR: A new era of complex thermoelectric materials is approaching because of modern synthesis and characterization techniques, particularly for nanoscale materials, and the strategies used to improve the thermopower and reduce the thermal conductivity are reviewed.
Abstract: Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. Such a development is contingent on identifying materials with higher thermoelectric efficiency than available at present, which is a challenge owing to the conflicting combination of material traits that are required. Nevertheless, because of modern synthesis and characterization techniques, particularly for nanoscale materials, a new era of complex thermoelectric materials is approaching. We review recent advances in the field, highlighting the strategies used to improve the thermopower and reduce the thermal conductivity.
8,999 citations
"Transition metal oxides – Thermoele..." refers background in this paper
...A detailed discussion on the substructuring approach is provided in another review[16]....
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...1 Bulk (3D) materials For bulk TMOs, the electrical conductivity can be defined in a simplistic form as follows:[16, 29]...
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...24 scavenging applications, an ideal TE TMO would comprise a high mobility semiconductor region entwined with a phonon scattering region that houses disordered structures (dopants and lack of stoichiometry), without affecting the carrier mobilities of the other region[16]....
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...Such manipulations change the vibrational properties of the crystal and influence κphonon[16] or by introducing additional scattering sites for phonons, thereby limiting κphonon[78-82]....
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...1 Bulk (3D) materials For semiconducting TMOs in bulk form, the simplified Seebeck coefficient can be estimated by the following expression:[16]...
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TL;DR: Titanium dioxide is the most investigated single-crystalline system in the surface science of metal oxides, and the literature on rutile (1.1) and anatase surfaces is reviewed in this paper.
7,056 citations
"Transition metal oxides – Thermoele..." refers background in this paper
...Many reviews on the various crystal structures, size and temperature dependence of the different polymorphs as well as different morphologies of stoichiometric and non-stoichiometric TiOx exists[119-121]....
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TL;DR: This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.
Abstract: We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire (NW) arrays. The aligned NWs are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the NW as a result of its bending. The rectifying characteristic of the Schottky barrier formed between the metal tip and the NW leads to electrical current generation. The efficiency of the NW-based piezoelectric power generator is estimated to be 17 to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.
6,692 citations
"Transition metal oxides – Thermoele..." refers background in this paper
...1 Crystal structure ZnO is the most widely investigated TMO for a wide variety of photovoltaic, sensing, optoelectronic, piezoelectric and TE applications[43, 180-183]....
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TL;DR: The dynamical mean field theory of strongly correlated electron systems is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition.
Abstract: We review the dynamical mean-field theory of strongly correlated electron systems which is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition. This mapping is exact for models of correlated electrons in the limit of large lattice coordination (or infinite spatial dimensions). It extends the standard mean-field construction from classical statistical mechanics to quantum problems. We discuss the physical ideas underlying this theory and its mathematical derivation. Various analytic and numerical techniques that have been developed recently in order to analyze and solve the dynamical mean-field equations are reviewed and compared to each other. The method can be used for the determination of phase diagrams (by comparing the stability of various types of long-range order), and the calculation of thermodynamic properties, one-particle Green's functions, and response functions. We review in detail the recent progress in understanding the Hubbard model and the Mott metal-insulator transition within this approach, including some comparison to experiments on three-dimensional transition-metal oxides. We present an overview of the rapidly developing field of applications of this method to other systems. The present limitations of the approach, and possible extensions of the formalism are finally discussed. Computer programs for the numerical implementation of this method are also provided with this article.
5,230 citations
"Transition metal oxides – Thermoele..." refers methods in this paper
...Many methods have been developed to address this issue, such as the dynamical mean-field theory (DMFT)[97] which has been successfully applied to the case of TMOs[98]....
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TL;DR: The thermal properties of carbon materials are reviewed, focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder, with special attention given to the unusual size dependence of heat conduction in two-dimensional crystals.
Abstract: Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range--of over five orders of magnitude--from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.
5,189 citations
Additional excerpts
...impurities, electrons, grain boundaries and interfaces[18]....
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