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Open access

S.S. Kim, I. Son and K.T. Kim

Abstract

In the present study, electroless Ni–P plating was applied to Bi–Te-based thermoelectric materials as a barrier layer and the effect of the Ni–P plating on the bonding strength of the thermoelectric module was investigated. The bonding strength of the n- and p-type modules increased after being subjected to the electroless Ni–P plating treatment. In the case of the thermoelectric module that was not subjected to electroless Ni–P plating, Sn and Te were interdiffused and formed a brittle Sn–Te-based metallic compound. The shearing mostly occurred on the bonding interface where such an intermetallic compound was formed. On the other hands, it was found from the FE-EPMA analysis of the bonding interface of thermoelectric module subjected to electroless Ni-P plating that the electroless Ni-P plating acted as an anti-diffusion layer, preventing the interdiffusion of Sn and Te. Therefore, by forming such an anti-diffusion layer on the surface of the Bi–Te based thermoelectric element, the bonding strength of the thermoelectric module could be increased.

Open access

Jaroslav Pršek and Dušan Peterec

hydrothermal system, Metaliferi Mts., Romania: Paragenesis and genetic significance. Mineralogical Magazine 68, 2, 301-321. COOK N.J., CIOBANU C.L., WAGNERT., STANLEY C.J., 2007: Minerals of the system Bi-Te-Se-S related to the tetradymite archetype: Review of classification and compositional variation. Canadian Mineralogist 45, 665-708. ĎUĎA R., ČERNÝ P., KALIČIAK M., KALIČIAKOVÁ E., TŐZSÉR J., ULRICH J., VESELOVSKÝ F., 1981: Mineralogy of the north part of the Slanské vrchy Mts. Mineralia Slovaca - Monograph

Open access

G. Kavei, K. Ahmadi, A. Shadmehr and A. Kavei

Abstract

(Bi2Te3)x(Sb2Te3)1−x solid solutions with x = 0:2, 0.25 and 0.3 − p type thermoelectric compounds with an excess of Tellurium dopant up to 4 wt% were crystallized. By increasing the Bi2Te3 content in the Bi-Sb-Te system, the hole concentration decreased and in consequence caused an optimum Seebeck coefficient and a decrease in electrical conductivity and thermal conductivity, thus resulting in an increase in the figure of merit at x = 0:25. The results showed that optimum thermoelectric properties can be achieved for a mixture of x = 0:25 with 3 wt% Te added. Structural characterizations of this compound in the absence and presence of the dopant were carried out by means of X-Ray diffraction measurement, scanning electron microscopy, electron backscattering diffraction and atomic force microscopy. Detailed analyses confirm that the improvements in thermoelectric parameters due to the intrinsic structure and minimum defects during crystallization of the compounds result from the excess of Te.

Open access

E.-B. Kim, J.-M. Koo and S.-J. Hong

Abstract

In this study, p-type Bi0.5Sb1.5Te3 based nanocomposites with addition of different weight percentages of Ga2O3 nanoparticles are fabricated by mechanical milling and spark plasma sintering. The fracture surfaces of all Bi0.5Sb1.5Te3 nanocomposites exhibited similar grain distribution on the entire fracture surface. The Vickers hardness is improved for the Bi0.5Sb1.5Te3 nanocomposites with 6 wt% added Ga2O3 due to exhibiting fine microstructure, and dispersion strengthening mechanism. The Seebeck coefficient of Bi0.5Sb1.5Te3 nanocomposites are significantly improved owing to the decrease in carrier concentration. The electrical conductivity is decreased rapidly upon the addition of Ga2O3 nanoparticle due to increasing carrier scattering at newly formed interfaces. The peak power factor of 3.24 W/mK2 is achieved for the base Bi0.5Sb1.5Te3 sintered bulk. The Bi0.5Sb1.5Te3 nanocomposites show low power factor than base sample due to low electrical conductivity.

Open access

S.-M. Yoon, B. Madavali, Y.-N. Yoon and S.-J. Hong

Abstract

In this work, p-type Bi0.5Sb1.5Te3 alloys were fabricated by high-energy ball milling (MA) and spark plasma sintering. Different revolutions per minute (RPM)s were used in the MA process, and their effect on microstructure, and thermoelectric properties of p-type Bi0.5Sb1.5Te3 were systematically investigated. The crystal structure of milled powders and sintered samples were characterized using X-ray diffraction. All the powders exhibited the same morphology albeit with slight differences find at 1100 RPM conditions. A slight grain size refinement was observed on the fracture surfaces from 500 to 1100 RPM specimens. The temperature dependence of Seebeck coefficient, electrical conductivity, and power factors were measured as a function of temperature with different RPM conditions. The power factor shows almost same (~3.5 W/mK2 at RT) for all samples due to unchanged Seebeck and electrical conductivity values. The peak ZT of 1.07 at 375K is obtained for 1100 RPM specimen due to low thermal conductivity.

Open access

Peyala Dharmaiah, C.H. Lee, B. Madavali and Soon-Jik Hong

Abstract

In the present work, we have prepared Bi2Te3 nanostructures with different morphologies such as nano-spherical, nanoplates and nanoflakes obtained using various surfactant additions (EG, PVP, and EDTA) by a hydrothermal method. The shape of the nanoparticles can be controlled by addition of surfactants. The samples were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that the minority BiOCl phase disappears after maintained pH at 10 with EG as surfactant. SEM bulk microstructure reveals that the sample consists of fine and coarse grains. Temperature dependence of thermoelectric properties of the nanostructured bulk sample was investigated in the range of 300-450K. The presence of nanograins in the bulk sample exhibits a reduction of thermal conductivity and less effect on electrical conductivity. As a result, a figure of merit of the sintered bulk sample reached 0.2 at 400 K. A maximum micro Vickers hardness of 102 Hv was obtained for the nanostructured sample, which was higher than the other reported results.

Open access

Joanna Kołodziejczyk, Jaroslav Pršek, Panagiotis Ch. Voudouris and Vasilios Melfos

References Bowell R.J., Foster R.P. & Stanley C.J. 1990: Telluride mineralization at Ashanti gold mine, Ghana. Mineral. Mag. 54, 617–627. Cepedal A., Martinez-Abad I., Fuertes-Fuente M. & Lima A. 2013: The presence of plumboan ingodite and a rare Bi-Pb tellurosulfide, Pb3Bi4Te4S5, in the Limarinho Gold deposit, Northern Portugal. Can. Mineral. 51, 643–651. Chang L.L.Y., Wu D. & Knowles C.R. 1988: Phase relations in the system Ag 2 S–Cu 2 S–PbS–Bi 2 S 3 . Econ. Geol. 83, 405–418. Ciobanu C.L. & Cook N.J. 2000: Intergrowths of bismuth

Open access

Maciej Rybicki

new bismuth telluride from British Columbia, with notes on wehrlite and some bismuth-tellurium alloys, University of Toronto Studies: VI. Geological Series, 49, 55-69 Zhao Y., Zhang Y., Bi C. (1999) Geology of gold-bearing skarn deposits in the middle and lower Yangtze River Valley and adjacent regions. Ore Geology Reviews, 14, 227-249.

Open access

Y. Bouachiba, A. Bouabellou, F. Hanini, F. Kermiche, A. Taabouche and K. Boukheddaden

Abstract

The mono and bi-layer TiO2 thin films have been prepared by sol-gel method on glass. X-Ray diffraction, Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and m-lines spectroscopy techniques have been used to characterize the TiO2 films. The mono-layer film is found to be amorphous, while the bi-layer film shows the presence of anatase phase. The bi-layer film exhibits more homogeneous surface with less roughness. The thickness effect on the refractive index, extinction ceofficient, packing density and optical band gap is analysed. The waveguiding measurements of the bi-layer film exhibit single-guided TE0 and TM0 polarized modes from which we can measure the refractive index and the film thickness.

Open access

Stanisław Z. Mikulski

sulphosaltsfromthe Larga hydrothennalsystem, Metaliferi Mts., Romania: Paragenesis and genetic significance. Mineralogical Magazine 68, s. 301-321. Cook, N.J. i Ciobanu,C. 2004b. Telluride metallogeny in the ‘Golden Quadrilateral' and beyond: Quovadis? [W:] Cook, N.J i Ciobanu, C.L. red. Gold-Silver-Telluride deposits ofthe Go Ide n Quadri la te rai. South Apu.se ni Mts., Romania. 1AGOD Guidebook Series vol. 12, s. 203-211. Domaszewska, T. 1965. Występowanie i eksploatacja złota na Dolnym Śląsku. Przegl. Geol. 13(4), s. 180