Effect of Vacancies on the Thermoelectric Properties of Mg2Si Containing Sb and Bi Substitution

2010 ◽  
Vol 1267 ◽  
Author(s):  
Titas Dasgupta ◽  
Christian Stiewe ◽  
Ralf Hassdorf ◽  
Lothar Boettcher ◽  
Eckhard Mueller
Keyword(s):  
Figure Of Merit ◽  
Phase Identification ◽  
Second Phase ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
Abundance Distribution ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Phonon Component ◽  
Constituent Elements

AbstractMg2Si1-xRx (R-Sb,Bi) compositions with x=0.025, 0.05 for Sb and x=0.01,0.025, 0.05 for Bi were synthesized by induction melting of the constituent elements followed by compaction by hot pressing. Phase identification by x-ray diffraction (XRD) indicate a biphasic nature for Bi substituted compositions for x≥.025 while solid solubility for the different Sb substitutions. Abundance distribution plots of the Seebeck (S) coefficient show asymmetry in the Sb compositions and is not observed in the Bi substituted samples. This indicates presence of vacancies only in the Sb substituted compositions. Electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (κ) values were measured from 300K to 773 K. The observed trends in the absolute values of α and S can be explained based on doping/second phase influence in Bi substitutions and due to effect of vacancies for Sb substitutions. The (κL) (phonon component) values show a significant decrease for the Sb substitutions due to the presence of vacancies. Calculation of the thermoelectric figure of merit (ZT) show a ZTmax of 0.56 for x=0.025 Bi composition compared to a ZTmax of ∼ 0.05 for Mg2Si.

scholarly journals Effects of Pr and Yb Dual Doping on the Thermoelectric Properties of CaMnO3

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1807 ◽  
Author(s):  
Cuiqin Li ◽  
Qianlin Chen ◽  
Yunan Yan
Keyword(s):  
Electron Microscopy ◽  
Figure Of Merit ◽  
Low Cost ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Transmission Electron ◽  
New Strategy ◽  
Low Toxicity

There has been research on CaMnO3 with natural abundance, low toxicity, and low cost as promising candidates for n-type thermoelectric (TE) materials. In this paper, Ca1−2xPrxYbxMnO3 with different Pr and Yb contents (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by means of coprecipitation. With X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), researchers characterized the phase structure and morphology of all the samples. The oxidation states of manganese were determined by X-ray photoemission spectroscopy (XPS). The role of Ca-site dual doping in the TE properties was also investigated. Increasing the Pr and Yb contents leads to decreases in the electrical resistivity and Seebeck coefficient, leading to a power factor of 3.48 × 10−4 W·m−1·K−2 for x = 0.04 at 773 K, which is its maximum. Furthermore, the thermal conductivity (κ) decreases with increasing x, and κ = 1.26 W m−1·K−1 is obtained for x = 0.04 at 973 K. Ca0.92Pr0.04Yb0.04MnO3 exhibit a ZT (thermoelectric figure of merit) value of 0.24 at 973 K, approximately 3 times more than that of the pristine CaMnO3. Thus, the reported method is a new strategy to enhance the TE performance of CaMnO3.

scholarly journals Thermoelectric Lead Telluride with ZnO Nanoparticles

2015 ◽  
Vol 16 (1) ◽  
pp. 62-67
Author(s):  
O. M. Matkivsky
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Figure Of Merit ◽  
Lead Telluride ◽  
Thermoelectric Figure Of Merit ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Zno Powder

An X-ray diffraction structural study and measurement of Seebeck coefficient (S), the electrical conductivity (σ) and thermal conductivity (χ) for Lead Telluride with nanoinclusions of ZnO. The calculated value of the specific thermoelectric power (S2σ) and thermoelectric figure of merit (ZT). It was established that the addition of ZnO powder Nanodispersed diameter grains (40-60) nm PbTe reduces the thermal conductivity of the material, and at 0.5 wt.% ZnO to an increase of lead telluride thermoelectric figure of merit to ZT≈1,3.

Enhanced thermoelectric properties of n-type Bi2Te2.7Se0.3 by indium and sodium co-doping

2015 ◽  
Vol 08 (01) ◽  
pp. 1550008 ◽  
Author(s):  
Xingkai Duan ◽  
Konggang Hu ◽  
Shifeng Ding ◽  
Dahu Man ◽  
Wangnian Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Testing Temperature ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Temperature Range ◽  
Co Doping ◽  
Seebeck Coefficients ◽  
Diffraction Effects

Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0, 0.02, 0.04, 0.06) and Bi 2 Te 2.7 Se 0.3 alloys were prepared by vacuum melting and hot pressing methods. The phase structure of the bulk samples were characterized by X-ray diffraction. Effects of indium and sodium co-substitutions for bismuth on the electrical and thermal transport properties were investigated in the temperature range of 298–473 K. Indium and sodium co-doping can enhance the carrier concentration, and accordingly the electrical conductivity can be improved effectively. The Seebeck coefficients of the co-doped samples have not been derogated strongly. The power factors are enhanced for the Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) within the whole testing temperature range. The Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) samples have the lower thermal conductivity due to reduction in lattice thermal conductivity, which leads to a great improvement in the thermoelectric figure of merit ZT. The highest ZT of the sample can reach 0.87 at 398 K.

A New Computer Algorithm for Qualitative X-Ray Powder Diffraction Analysis

1981 ◽  
Vol 25 ◽  
pp. 213-219 ◽  
Author(s):  
T. C. Huang ◽  
W. Parrish
Keyword(s):  
Figure Of Merit ◽  
Internal Standard ◽  
Systematic Errors ◽  
Computer Algorithm ◽  
Polycrystalline Materials ◽  
Phase Identification ◽  
Automatic Correction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Jcpds File

AbstractAn effective and practical computer algorithm has been developed for rapid and precise phase identification of polycrystalline materials by X-ray diffraction methods using the JCPDS database and/or user created standard files. The entire JCPDS file was reorganized for efficient search. Identifications are facilitated by a number of options: automatic correction of systematic errors using internal standard reflections, selectable window widths for file searching, elemental restrictions (chemical prescreening), handling preferred orientation, match without using intensities, match with 3 reflections, and others. A comprehensive algorithm for calculating a figure-of-merit (FOM) is used so that the “correct” phases can easily be identified with highest FOMs. This method has been tested extensively on a wide variety of analyses and is applicable to either a host or a minicomputer.

Effects of indium-filling and synthesis pressure on the thermoelectric properties of CoSb3

2014 ◽  
Vol 28 (15) ◽  
pp. 1450118 ◽  
Author(s):  
Le Deng ◽  
Li Bin Wang ◽  
Jie Ming Qin ◽  
Tao Zheng ◽  
Xiao Peng Jia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Processing Time ◽  
Room Temperature ◽  
Thermoelectric Figure Of Merit ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Scanning Electron

In x Co 4 Sb 12 skutterudite compounds have been prepared successfully at different synthesis pressures by high pressure and high temperature (HPHT) method, the processing time has been reduced from a few days to half an hour. In addition, the effect of synthesis pressure on the thermoelectric properties of In 0.4 Co 4 Sb 12 compounds has been investigated in this paper. The structure of In 0.4 Co 4 Sb 12 samples was evaluated by means of X-ray diffraction and scanning electron microscopy (SEM). The Seebeck coefficient, electrical resistivity and thermal conductivity were all measured in the temperature range of room temperature to 673 K. The sample synthesized at 2.0 GPa showed the highest power factor of 29.3 μWcm-1K-2 at 373 K. A dimensionless thermoelectric figure of merit (ZT) of 0.51 at 673 K was achieved for n-type In 0.4 Co 4 Sb 12 prepared at 1.3 GPa, which was significantly enhanced in comparison with pure CoSb 3.

scholarly journals Synthesis and Properties of Highly Efficient Thermoelectric Materials Based on Lead Telluride with Antimony and Silver Impurity

2015 ◽  
Vol 16 (1) ◽  
pp. 49-54
Author(s):  
D. M. Freik ◽  
S. І. Mudriy ◽  
Ts. A. Kriskov ◽  
І. V. Gorіchok ◽  
O. M. Matkіvsky ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Figure Of Merit ◽  
Thermal Conductivity Coefficient ◽  
Lead Telluride ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Thermoelectric Coefficient ◽  
Thermoelectric Parameters

The paper presents the results of research of X-ray diffraction and thermoelectric parameters (thermoelectric coefficient α, electrical conductivity σ and thermal conductivity coefficient k) of materials based on Lead Telluride: PbTe, PbTe:Sb, PbTe-Sb2Te3, Pb18Ag1Sb1Te20, Pb18Ag2Te20 and PbTe-Ag2Te. Established that the highest values of thermoelectric figure of merit have samples of PbTe:Sb (0,3 at.%) and system Pb18Ag1Sb1Te20, Pb18Ag2Te20. For PbTe:Sb is due to a significant increase of the electrical conductivity. For the other two materials is due to a increase the thermoelectric coefficient and a significant decrease of thermal conductivity compared to pure PbTe.

scholarly journals An Insight into Chemistry and Structure of Colloidal 2D-WS2 Nanoflakes: Combined XPS and XRD Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1969
Author(s):  
Riccardo Scarfiello ◽  
Elisabetta Mazzotta ◽  
Davide Altamura ◽  
Concetta Nobile ◽  
Rosanna Mastria ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Xrd Analysis ◽  
Crystal Habit ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Evaluation ◽  
Rational Understanding ◽  
Structural Inspection

The surface and structural characterization techniques of three atom-thick bi-dimensional 2D-WS2 colloidal nanocrystals cross the limit of bulk investigation, offering the possibility of simultaneous phase identification, structural-to-morphological evaluation, and surface chemical description. In the present study, we report a rational understanding based on X-ray photoelectron spectroscopy (XPS) and structural inspection of two kinds of dimensionally controllable 2D-WS2 colloidal nanoflakes (NFLs) generated with a surfactant assisted non-hydrolytic route. The qualitative and quantitative determination of 1T’ and 2H phases based on W 4f XPS signal components, together with the presence of two kinds of sulfur ions, S22− and S2−, based on S 2p signal and related to the formation of WS2 and WOxSy in a mixed oxygen-sulfur environment, are carefully reported and discussed for both nanocrystals breeds. The XPS results are used as an input for detailed X-ray Diffraction (XRD) analysis allowing for a clear discrimination of NFLs crystal habit, and an estimation of the exact number of atomic monolayers composing the 2D-WS2 nanocrystalline samples.

scholarly journals New Zn3Mg-xY Alloys: Characteristics, Microstructural Evolution and Corrosion Behavior

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2505
Author(s):  
Catalin Panaghie ◽  
Ramona Cimpoeșu ◽  
Bogdan Istrate ◽  
Nicanor Cimpoeșu ◽  
Mihai-Adrian Bernevig ◽  
...  
Keyword(s):  
Galvanic Corrosion ◽  
Intermetallic Phase ◽  
Young Modulus ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
Medical Field ◽  
Pure Zinc ◽  
X Ray ◽  
Knowing That ◽  
Master Alloys

Zinc biodegradable alloys attracted an increased interest in the last few years in the medical field among Mg and Fe-based materials. Knowing that the Mg element has a strengthening influence on Zn alloys, we analyze the effect of the third element, namely, Y with expected results in mechanical properties improvement. Ternary ZnMgY samples were obtained through induction melting in Argon atmosphere from high purity (Zn, Mg, and Y) materials and MgY (70/30 wt%) master alloys with different percentages of Y and keeping the same percentage of Mg (3 wt%). The corrosion resistance and microhardness of ZnMgY alloys were compared with those of pure Zn and ZnMg binary alloy. Materials were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), linear and cyclic potentiometry, and immersion tests. All samples present generalized corrosion after immersion and electro-corrosion experiments in Dulbecco solution. The experimental results show an increase in microhardness and indentation Young Modulus following the addition of Y. The formation of YZn12 intermetallic phase elements with a more noble potential than pure Zinc is established. A correlation is obtained between the appearance of new Y phases and aggressive galvanic corrosion.

Nanostructured TiO2-Based Composites for Light Absorption

2014 ◽  
Vol 975 ◽  
pp. 207-212
Author(s):  
Dayse I. dos Santos ◽  
Olayr Modesto Jr. ◽  
Luis Vicente A. Scalvi ◽  
Americo S. Tabata
Keyword(s):  
Metal Oxide ◽  
Light Absorption ◽  
Structural Characteristics ◽  
Sol Gel ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Oxide Powders

Metal oxide nanocomposites were prepared by two different routes: polyol and sol-gel. Characterization by X ray diffraction showed that the first process produces directly a two-phase material, while the sol-gel powder never showed second phase below 600°C. Light spectroscopy of the treated powders indicated similarities for the processed materials. Although the overall material compositions are about the same, different structural characteristics are found for each processing. With the exception of Ti-Zn materials, all the double metal oxide powders showed higher absorbance than either TiO2 powder.

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