Electronic Structure and Thermoelectric Properties of AxMo3Sb5Te2

2003 ◽  
Vol 793 ◽  
Author(s):  
Navid Soheilnia ◽  
Holger Kleinke
Keyword(s):  
Thermal Conductivity ◽  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Thermoelectric Properties ◽  
Gap Size ◽  
Formula Unit ◽  
Chemically Modified ◽  
Thermoelectric Energy ◽  
Attractive Candidate

ABSTRACTMo3Sb7 may be chemically modified to become semiconducting by replacing two Sb atoms with two Te atoms (per formula unit). This material may be an attractive candidate for the thermoelectric energy conversion, as its thermal conductivity may be lowered by creating the rattling effect upon intercalation of small cations, and its band structure may be tailored, i.e. the band gap size modified. The higher the Te content and the higher the cation amount, the smaller is the band gap, which can virtually reach any value below 0.5 eV.

Band Structure and Thermoelectric Properties of Ni(x)Zn(1-x)Fe2O4

2021 ◽  
Vol 317 ◽  
pp. 28-34
Author(s):  
Joon Hoong Lim
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Band Structure ◽  
Seebeck Coefficient ◽  
Band Gap ◽  
Thermoelectric Properties ◽  
Xrd Analysis ◽  
Valence Band Maximum ◽  
Solid State Method ◽  
Ni Content

Thermoelectric materials has made a great potential in sustainable energy industries, which enable the energy conversion from heat to electricity. The band structure and thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 have been investigated. The bulk pellets were prepared from analytical grade ZnO, NiO and Fe2O3 powder using solid-state method. It was possible to obtain high thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 by controlling the ratios of dopants and the sintering temperature. XRD analysis showed that the fabricated samples have a single phase formation of cubic spinel structure. The thermoelectric properties of Ni(x)Zn(1-x)Fe2O4 pellets improved with increasing Ni. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The electrical conductivity of Ni(x)Zn(1-x)Fe2O4 (x = 0.0) is (0.515 x10-3 Scm-1). The band structure shows that ZnxCu1-xFe2O4 is an indirect band gap material with the valence band maximum (VBM) at M and conduction band minimum (CBM) at A. The band gap of Ni(x)Zn(1-x)Fe2O4 increased with increasing Ni content. The increasing band gap correlated with the lower electrical conductivity. The thermal conductivity of Ni(x)Zn(1-x)Fe2O4 pellets decreased with increasing Ni content. The presence of Ni served to decrease thermal conductivity by 8 Wm-1K-1 over pure samples. The magnitude of the Seebeck coefficient for Ni(x)Zn(1-x)Fe2O4 pellets increased with increasing amounts of Ni. The figure of merit for Ni(x)Zn(1-x)Fe2O4 pellets and thin films was improved by increasing Ni due to its high Seebeck coefficient and low thermal conductivity.

CHANGES INDUCED IN THE SURFACE ELECTRONIC STRUCTURE OF Be(0001) AFTER Si ADSORPTION

2002 ◽  
Vol 09 (02) ◽  
pp. 687-691
Author(s):  
L. I. JOHANSSON ◽  
C. VIROJANADARA ◽  
T. BALASUBRAMANIAN
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Electronic Properties ◽  
Surface State ◽  
Core Level ◽  
Clean Surface ◽  
Core Level Spectrum ◽  
Surface Band ◽  
Surface Electronic Structure

A study of effects induced in the Be 1s core level spectrum and in the surface band structure after Si adsorption on Be(0001) is reported. The changes in the Be 1s spectrum are quite dramatic. The number of resolvable surface components and the magnitude of the shifts do decrease and the relative intensities of the shifted components are drastically different compared to the clean surface. The surface band structure is also strongly affected after Si adsorption and annealing. At [Formula: see text] the surface state is found to move down from 2.8 to 4.1 eV. The band also splits at around 0.5 Å-1 along both the [Formula: see text] and [Formula: see text] directions. At [Formula: see text] and beyond [Formula: see text] only one surface state is observed in the band gap instead of the two for the clean surface. Our findings indicate that a fairly small amount of Si in the outer atomic layers strongly modifies the electronic properties of these layers.

Resonance levels in GeTe thermoelectrics: zinc as a new multifaceted dopant

2020 ◽  
Vol 44 (41) ◽  
pp. 17664-17670
Author(s):  
D. Krishna Bhat ◽  
U. Sandhya Shenoy
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Thermoelectric Properties ◽  
Resonance States ◽  
Structure Engineering

Electronic-structure engineering of GeTe:Zn doping enhances thermoelectric properties via synergy of resonance states, increase in band gap and hyper-convergence.

Thermoelectric properties of Ge doped n-type TixZr1−xNiSn0.975Ge0.025 half-Heusler alloys

2015 ◽  
Vol 3 (23) ◽  
pp. 12507-12514 ◽  
Author(s):  
Yuanfeng Liu ◽  
Pierre F. P. Poudeu
Keyword(s):  
Thermal Conductivity ◽  
Band Gap ◽  
Thermoelectric Properties ◽  
Heusler Alloys

Manipulating the band gap of ZrNiSn (half-Heusler) alloys through isoelectronic substitutions at Ti/Zr and Sn/Ge sites, and nanostructuring afford a simultaneous enhancement of thermopower and reduction in thermal conductivity leading to a significant increase in the ZT value.

Thermoelectric properties and thermal stability of layered chalcogenides, TlScQ2, Q = Se, Te

2017 ◽  
Vol 46 (48) ◽  
pp. 17053-17060 ◽  
Author(s):  
Vijayakumar Sajitha Aswathy ◽  
Cheriyedath Raj Sankar ◽  
Manoj Raama Varma ◽  
Abdeljalil Assoud ◽  
Mario Bieringer ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Band Structure ◽  
Thermoelectric Properties ◽  
Layered Chalcogenides ◽  
Low Thermal Conductivity ◽  
Structure Characteristics ◽  
Thermal Stability Of

The layered chalcogenides, TlScQ2 (Q = Se, Te), possess intriguing band structure characteristics and very low thermal conductivity.

Atomic and Electronic Structure of LaAlO3 and LaAlO3:Mg from First-Principles Calculations

2009 ◽  
Vol 79-82 ◽  
pp. 1257-1260
Author(s):  
Li Guan ◽  
Li Tao Jin ◽  
Wei Zhang ◽  
Qiang Li ◽  
Jian Xin Guo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Lattice Structure ◽  
Cell Structure ◽  
Functional Theory ◽  
Super Cell ◽  
Direct Band ◽  
Experimental Values

In the present paper, the lattice structure, band structure and density of state of LaAlO3 and LaAlO3:Mg are calculated by first-principle method based on density functional theory. Firstly, we select the different cutoff energy and k-point grid in the calculations, and obtain the most stable geometry structure of single crystal LaAlO3. The calculated lattice parameters are a=b=5.441 Å, c=13.266 Å, which matches with experimental values. To deeply understand the electronic structure of LaAlO3, a 2×1×1 super-cell structure is established and the doping concentration of Mg at Al sites is 25%. From the band structure and density of states, it can be seen that LaAlO3 has a direct band gap Eg=3.6 eV. However, LaAlO3:Mg has a larger band gap Eg=3.89 eV and the Fermi level enters into the valence band, which indicates the holes are introduced. The calculated results show that the conductivity of LaAlO3:Mg is better than pure LaAlO3, which is in good agreement with experimental results.

First-Principles Study on Electronic Structure of 15R-SiC Polytypes

2014 ◽  
Vol 971-973 ◽  
pp. 77-80 ◽  
Author(s):  
Fu Chun Zhang ◽  
Ying Gao ◽  
Hong Wei Cui ◽  
Xing Xiang Ruan ◽  
Wei Hu Zhang
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Charge Density ◽  
Band Gap ◽  
Density Functional ◽  
Covalent Bond ◽  
Lattice Parameter ◽  
Pseudopotential Approach ◽  
Structure Density ◽  
Indirect Band Gap

To study the geometrical and electronic structure of 15R-SiC polytypes, the lattice parameter, band structure, density of states (DOS) and charge density of 15R-SiC are calculated by using density functional theory based on the plane wave pseudopotential approach, and electronic structure and ground properties of 15R-SiC are investigated by the calculated band structure and DOS, the results show that 15R-SiC is an indirect band gap semiconductor, with calculated indirect band gap width being 2.16 eV and band gap dependent on Si 3p and C 2p states. While charge density results show that Si-C bond is a hybrid bond semiconductor strong in covalent bond and weak in ionicity, characterized by intense sp3 hybrid characteristics, which is in accordance with the experimental results. The above mentioned results are considered as theoretical reference for design and application of SiC polytype materials.

In-Plane Thermal and Thermoelectric Properties of Polycrystalline Highly Preferred Orientation [(W)x(WSE2)y]z Superlattice Thin Films

2007 ◽  
Author(s):  
Anastassios Mavrokefalos ◽  
Ngoc T. Nguyen ◽  
Michael T. Pettes ◽  
David C. Johnson ◽  
Li Shi
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Time Domain ◽  
Preferred Orientation ◽  
Laser Reflectance ◽  
Thermoelectric Energy ◽  
Measurement Results ◽  
The Time Domain

It was recently found by using the time domain thermal reflectance method that polycrystalline highly preferred orientation WSe2 and [(W)x(WSe2)y]z superlattice films possess extremely low cross-plane thermal conductivity, which is desirable for thermal insulation and thermoelectric energy conversion applications. However, it is difficult to obtain the in-plane thermal conductivity by using the laser reflectance or the 3-ω method. Here we employ a suspended microdevice developed for measuring thermoelectric properties of individual nanowires and nanofilms to obtain the in-plane thermal conductivity, electrical conductivity, and Seebeck coefficient of [(W)x(WSe2)y]z superlattice films. The measurement results show that the in-plane thermal conductivities of these films are much higher than the cross-plane values, making the thermal conductivity of the films highly anisotropic.

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