Hittite Journal of Science and Engineering, 2018, 5 (4) 293-299 ISSN NUMBER: 2148-4171 DOI: 10.17350/HJSE19030000106

Development of Nanostructure Pellet for Thermoelectric Applications

Hayati Mamur1 M.R.A. Bhuiyan2 1Department of Electrical and Electronics Engineering, Manisa Celal Bayar University, Manisa, Turkey 2Department of Electrical and Electronic Engineering, Islamic University, Kushtia, Bangladesh

Article History: ABSTRACT Received: 2017/10/19 Accepted: 2018/05/01 Online: 2018/05/24 he bismuth telluride (Bi2Te 3) nanostructure powders and pellet was successfully devel- Toped for thermoelectric applications by using a simple chemical process. Several char- Correspondence to: Hayati Mamur, acterization tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Department of Electrical and Electronics Engineering, Manisa Celal Bayar energy dispersive X-ray (EDX), atomic force microscopy (AFM) and Fourier transform University, Manisa, Turkey infrared (FT-IR) spectrometry were carried out. The XRD, SEM, EDX, and FTIR analy- E-Mail: [email protected]

ses showed that the chemical structure of pellet is Bi2Te 3. The average crystalline size of

the Bi2Te 3 pellet is found to be 3.93 nm, as determined by the SEM. The AFM studies confirmed that the pellet is of nanostructure form and average surface roughness value is 68.06 nm. This is within the roughness range which can lead to an enhancement in

thermoelectric properties of Bi2Te 3 nanostructure. This could be evidenced by thermal conductivity which should be higher than the electrical conductivity.

Keywords:

Bismuth telluride (Bi2Te 3); Nanostructure pellet; Chemical process; Microstructural properties; Thermoelectric

INTRODUCTION

he bismuth telluride (Bi2Te 3) is an efficient ther- However, there are few studies about this [18,19]. For Tmoelectric (TE) type material. this reason it is a challenging task to develop the single When the post transition metal elements of bismuth crystal Bi2Te 3 nanostructure materials. Development of (Bi) is alloyed with a non-metal elements of the nanostructured thermoelectric material is firmly (Te) then it makes a compound semicon- connected to the capability to find out the microstruc-

ductor material, Bi2Te 3. An acceptable TE material tural and optical characterization. is indicated by large density and mobility of charge carriers, at the coinciding by the low thermal conduc- In this paper, a simple chemical method was tried

tivity and high electrical conductivity. Another att- to develop the Bi2Te 3 nanostructure pellet for thermoe- ractive aspect is that the efficient energy conversion lectric applications. In the studies presented previously adaptability of a TE material is performed by the ex- [20-23], this method was compared with other elect- tensive dimensionless figure of merit: ZT = (S2σT)/K, rochemical synthesis methods. Ultimately, the recom- where S is the , σ is the electrical mended method was suitable for the producing nanost- conductivity, K is the thermal conductivity and T is ructure material. Furthermore, the superiority of this the temperature. method was demonstrated via comparing with other methods in two reviewed papers [24, 25]. In this paper

Nowadays, Bi2Te 3 nanostructure has a great deal of handling a development of Bi2Te 3 nanostructure pellet interest in thermoelectric applications such as thermo- for TE applications, after the first introduction, experi- electric heating and cooling, thermoelectric generators mental methods was presented in the second section. In and portable power supply [1-10]. Recent studies suggest the third section, the results and discussion section was

that Bi2Te 3 material usage in nanostructure form ge- given. Finally, the conclusion and future research secti- nerates the higher ZT (from 0.62 to 1.13) values [11-17]. on were clarified. H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299 h raet o Bi(NO of reagents The (Analytical grade, Mark) were also supplied and used wit used and supplied were also Mark) grade, (Analytical %, Sigma Aldrich), NaBH Aldrich), Sigma %, Developed Bi EXPERIMENTAL METHODS EXPERIMENTAL Other flux was fulfilled with 15 mmol (1.134 gm) NaBH gm) (1.134 mmol 15 with fulfilled was flux Other vacuum furnace at 180 at furnace vacuum Sigma Aldrich and used as starting materials for the co- the for materials starting as used and Aldrich Sigma value of the solution. of the value of Bi of one flux (sol. 1) and other flux has been fulfilled with NaOH with fulfilled (sol.been has 1)one flux flux other and dried in an oven dried at 80 washed were black on. precipitates collected, The developed oxidization. The chemicals were weighed according to their to their according were weighed chemicals The oxidization. 3) at 80 of Bi:Te (2:3) for the co-precipitation. NaOH was utilized utilized Bi:Teof was NaOH co-precipitation. (2:3) the for The method. this in materials starting the as employed white precipitates were grown in a flux. 150 ml white preci white ml 150 flux. a in grown were precipitates white stirring, magnetic After hour. an half for stirring magnetic by developed was co-precipitation complete and mosphere ness was made. The manufactured pellets are sequentially sequentially are pellets manufactured The made. was ness thick mm 1 and diameter cm 1 having pellet nanostructure netic stirrer for 15 minute (sol. 4). The sol. 3 and sol. 4 was was 4 sol. and 3 sol. The 4).(sol. minute 15 for stirrer netic pitates were collected and reserved in a borosilicate flux (sol. flux a in borosilicate reserved and were pitates collected powder was put in a 1 cm diameter pellet base and was pres was and base pellet a put 1 diameter in cm powder was precipitation of a simple chemical solution method. The The method. solution chemical simple a of precipitation at room temperature with adjusted the hydro dynamic at dynamic hydro the adjusted with temperature room at and deionized water to remove the byproducts thereafter thereafter byproducts the remove to water deionized and using times several in centrifuged by separated and n TeO and and 3 mmol (0.47 3 mmol TeO gm) and solution of (3 M = 30 gm) NaOH was employed for pH va pH for employed was NaOH gm) 30 = M (3 of solution solution (sol. 2). These two solutions was mixed together together mixed was solutions two These 2). (sol. solution sed 5 MPa pressure. Then the formed pellet was heated in a a in heated was pellet formed the Then pressure. MPa 5 sed same conditions and black colour precipitate was developed developed was precipitate colour black and conditions same stoichiometry (Bi stoichiometry solution of 100 ml distilled water at 80ºC soluble by mag by soluble 80ºC at water distilled ml 100 of solution shown in Fig. 1. Fig. in shown solvents of HNO of solvents starting materials were taken with stoichiometric ratio ratio stoichiometric with taken were materials starting lue regulated. The two metallic solutions were reserved in in reserved were solutions metallic two The regulated. lue tal ion solutions by using 2 mmol (0.97 gm) Bi(NO gm) (0.97 mmol 2 using by solutions ion tal by magnetic stirring for four hours to remove the oxidizati the remove to hours four for stirring magnetic by to precipitates of to BiONO precipitates blended together at the 80 at the together blended hout any further purification. In advance of the synthesis of synthesis the In advance purification. hout any further handled in concentrated (2 M = 31.86 ml) HNO ml) 31.86 = M (2 concentrated in handled The Bi and Te oxides were eliminated by using NaBH using by eliminated were Te and oxides Bi The The The NaBH 2 Te o C by using the magnetic stirrer for several minutes. for several stirrer magnetic the C byusing 3 aotutr, Bi(NO nanostructure, 2 (≥97%, Sigma Aldrich) were purchased form form purchased were Aldrich) Sigma (≥97%, 4 2 was used as was used a reducing agent for remove the Te 2 3 Te (65%, Sigma Aldrich), NaOH (98-100 NaOH Aldrich), Sigma (65%, 3 nanostructure pellet 3 o =2:3) and were prepared separate me separate prepared were and =2:3) C for 18 In hours. the end, the product o C for two hours. Finally, the Bi the Finally, hours. two for C 3 ) 3 o 3 and TeO and 4 C temperature with adjusted the the adjusted with C temperature 2 .5H (98-100 %, mark) and Ethanol Ethanol and mark) (98-100%, . Dissolving these materials was was materials these . Dissolving 2 O (≥98%, Sigma Aldrich) Aldrich) Sigma (≥98%, O 3 ) 3 .5H 2 and regulated the pH and regulated 2 O and TeO and O 3 . A stock stock A . 3 ) 3 2 .5H were were 2 Te 2 O 4 4 3 ------.

29 4 The improvement of the TE materials into next generati next into materials TE the of improvement The The XRD patterns were recorded by using a X’Pert high high X’Pert a using by recorded were patterns XRD The MP CCD cameras by an atomic force microscopy. BRU microscopy. force atomic an by cameras CCD MP RESULTS AND DISCUSSIONRESULTS AND KER TENSOR II spectrometry was used for FTIR measu for FTIR used was spectrometry II TENSOR KER Experimental techniques Experimental operated at 45 kV and 40 mA, with angular range 05º ≤2 05º range angular with mA, kV at 40 45 and operated hrceiain ehius n tertcl oes for models theoretical and techniques characterization new of improvement the on depends crucially devices on aotutr. tpcl R setu o Bi of spectrum XRD typical A nanostructure. ructure pellet is shown in Fig. 2a. Fig. 2b shows the compare Fig. Fig. in shown 2b 2a. is shows compare the pellet ructure rements. topographic 3D system. VP 1430 LEO of (EDX) roscopy X-ray spect dispersive energy (SEM) and microscopy ron rence length as a function of direction. Their results are are results Their direction. of function a as length rence averaged over a large volume giving an overall view of the the of view overall an giving volume large a over averaged score PANalytical diffractometer with Cu-K with diffractometer PANalytical score td o te pcrm ih sadr rfrne oe 98- code reference standard a with spectrum the of study structure andstructure characteristics. surface were 10using surface recorded in 0.01 nm discrimination the initial understanding of the relationship between the the between relationship the of understanding initial the tion of the pellet was accomplished with a scanning elect a scanning with accomplished was of pellet tion the the nanostructure materials by showing the average cohe average the showing by materials nanostructure the 018-4631 for Bi Figure 1. θ

≥ 85º. The morphology and elemental atomic composi atomic elemental and 85º. ≥ morphology The The XRD provides complimentary information about about information complimentary provides XRD The The manufacture of pellets is shown sequentially shown is pellets of manufacture The 2 Te 3 . α 2 Te radiation, radiation, 3 nanost ------equation [26], simplified by other researcher byother [26],equation simplified - There radian. into converted be should B of unit The peak. fore the above equation takes the form: the takes equation above fore the line with a (015) preferred orientation. By using the Scherrer a (015)Scherrer the with By line using orientation. preferred is the full-width half-maximum (FWHM) of high intensity intensity high of (FWHM) half-maximum full-width the is Figure 2. The XRD revealed that the structure was nanocrystal was structure the that revealed XRD The where, where, B B crystalline crystalline XRD spectrum of Bi of spectrum XRD λ = = is the wavelength of Cu-K wavelength the is 50.97 B B 0.94 cos cos λ θ θ λ

2 Te 3 nanostructure pellet. nanostructure α radiation, and B B and radiation, (2) (1) - 29 5 of merit, ZT. Recently, due to its capability of converting converting of capability its to due Recently, ZT. merit, of der to compare the spectrum with the Bi with der to the spectrum compare waste heat into electricity, thermoelectric applications have have applications thermoelectric electricity, into heat waste aeil i sial fr hrolcrc plctos I or In applications. thermoelectric for suitable is materials nm, which conformed reasonably well to the literature va literature the to well reasonably conformed which nm, trce icesn itrs. n hs vriw a thermoe a overview, this In interest. increasing attracted figure thermoelectric the on effect detrimental a has and average crystalline size of the pellet was calculated to size of be 3.93 the calculated was pellet average crystalline standard reference code, three peaks (015),(1010) (110)peaks and three code, reference standard thermal conductivity but their high resistivity dominates dominates resistivity high their but conductivity thermal lowest the have materials crystallites smallest [27]. The lue lectric material with size effect, specifically low dimensional low dimensional specifically effect, size with material lectric The calculated value shows the crystalline size. The The size. crystalline the shows value calculated The 2 Te 3 nanostructure nanostructure - - -

H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299 H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299 A preliminary electron diffraction study indicated that the the that indicated study diffraction electron preliminary A The homogeneity of the sample was arranged sequentially. sequentially. arranged was sample the of homogeneity The quartz crystal chamber atmosphere. chamber crystal quartz Bi f h seie b rsoig fcsd lcrn em ac beam electron focused a restoring by specimen the of opsto, rsaln srcue n oinain f ma of orientation and structure crystalline composition, about information the reveal signals The signals. electron oxidization form. When an atom is oxidized, its characteris its oxidized, atom is an When form. oxidization ded that the produced powder should be passed in 99% pure pure in 99% ded the produced that powder be should passed were similar. Other two peaks (205) and (2011)(205) and peaks two were Other slightly were similar. mize the oxidization and obtain pure Bi pure obtain and oxidization the mize ross the surface and detecting secondary or backscattered backscattered or secondary detecting and surface the ross rature [28], one report was issued that the pure H pure the that issued was report [28],one rature roscope identifies the specimen of interest. Table 1 shows shows 1 Table interest. of specimen the identifies roscope pellets, before construct the pellets, it has been recommen been has it pellets, the construct before pellets, passed to synthesize Bi synthesize to passed form of Bi form free materials that the materials are pure form. In the lite the In form. pure are materials the that materials free atomic stoichiometric ratio (34.62:51.52). From this table, it it table, (34.62:51.52). From this ratio stoichiometric atomic and microstructural information about the prepared pellets. pellets. about prepared the information microstructural and sample at 400ºC for 2 hours. In order to overcome or mini or overcome to order In hours. 2 for 400ºC at sample shifted to the reference code. The peaks did not match the the match not did peaks The code. reference the to shifted samples were quasi spherical granule shapes in agglomera in shapes granule spherical quasi were samples ture. The materials of Bi and Te were arranged with their their with arranged were Te and Bi of materials The ture. terials. Fig. 3 shows the SEM image for the morphological morphological the for image SEM the shows 3 Fig. terials. chemical morphology, external including specimen the tics tics may be to wants Every change. researcher produce oxide the elemental atomic composition of the Bi the of composition atomic elemental the mic the of capability image the where instruments SEM to attachments are systems The materials. of composition tal [29]. report previous the with agreement in te qui were results The nature. in crystalline with clusters ted hydrogen (H hydrogen Figure 3. 2 Te According to the XRD result, the pellets may be some some be may pellets the result, XRD the to According SEM provides the detailed high resolution images images resolution high detailed the provides SEM EDX is an x-ray technique used to identify the elemen the identify to used x-raytechnique an is EDX 3 nanostructure. The peaks matched with other oxides other oxides with matched The peaks nanostructure. SEM image of Bi of image SEM 2 Te 2 3 ) or nitrogen (N nitrogen or ) materials. 2 Te 2 Te 3 nanostructure pellet nanostructure 3 nanostructure throughout the the throughout nanostructure 2 ) gas at 250ºC for 2 hours in a a in hours 2 for 250ºC at gas ) 2 Te 3 nanostructure nanostructure 2 Te 3 nanostruc 2 gaswas ------29 6 observed in this sample. In order to reduce the impurities impurities the reduce to order In sample. this in observed depositional contaminants by isolating the pellet fractions fractions pellet the isolating by contaminants depositional Table 1. was followed. was was confirmed that ultra–fine device quality Bi quality device ultra–fine that confirmed was which indicates the little amount of contamination of the the of contamination of amount little the indicates which nation may be artificially caused, it occurs in the post–de the in occurs it caused, artificially be may nation recommendation indicated the XRD investigation section section investigation XRD the indicated recommendation ructure. The materials of Bi The and materials Te ructure. their with were arranged the that clear also is It developed. been has pellet ructure good agreement with other researchers' report [30]. The The [30]. report researchers' other with agreement good pellet. H pellet. Te. and Bi of form stoichiometric contains pellet positional environment. It post– removing is environment. with concerned positional a sharp probe (<10 nm) and surface at very little distance distance little very at surface and nm) (<10 probe sharp a and the obtained pure Bi pure obtained the and surface on a nano scale size by measuring forces between between forces measuring by size scale nano a on surface some other impurities such as carbon and oxygen were were oxygen and carbon as such impurities other some found also were Te.results and Moreover,same Bi of sisted spectrum shows the other peck that is carbon and oxygen oxygen and carbon is that peck other the shows spectrum cleared was it curve these From form. (2:3) stoichiometric thermal condition was recommended. In here, the previous previous the here, In recommended. was condition thermal h efcs f otdpstoa cnaiain Contami contamination. post–depositional of effects the that containing a very small amount of carbon and oxygen. and of carbon amount small avery containing that Bi that in the other researcher reports [31]. In this investigation, investigation, this In [31]. reports researcher other the in is being mixed with the metal solution, the accurate hydro hydro accurate the solution, metal the with mixed being is Figure 4. Tellerium AFM demonstrates a 3D image of the produced pellet pellet produced the of image 3D a demonstrates AFM t a as epesd ht Bi that expressed also was It i. sos h EX pcrm f h Bi the of spectrum EDX the shows 4 Fig. Bismuth Element Oxygen Carbon The atomic composition of the Bi the of composition atomic The 2 Te EDX spectrum of Bi of EDX spectrum 2 gas passing throughout the pellet at ~250ºC that that ~250ºC at pellet the throughout passing gas 3 nanostructure were developed which was in in was which developed were nanostructure Total: 100.00% M series 2 K series K series L series 2 Te Series Te 3 3 nanostructure pellet nanostructure nanostructure pellet, while it it while pellet, nanostructure 2 2 Te Te 3 nanostructure. 3 aotutrs con nanostructures Atom.[at.%] 2 34.62 51.52 2 10.13 Te 3.73 Te 3 3 nanost nanost - - - - - AFM measurements were another confirmation that the the that confirmation another were measurements AFM The surface roughness increases the efficiency of the heat heat the of efficiency the increases roughness surface The nanostructure pellet nanostructure enhancement if one has rough surfaces in nano size mate size nano in surfaces rough has one if enhancement show may ZT Therefore, contributions. bulk and sum surface of the in factor weight higher has it that fact the to due conductivity can be manipulated almost independently wit independently almost manipulated be can conductivity thermal the of part phonon the only Therefore, connected. materials. Therefore, the surface roughness may also corre also may roughness surface the Therefore, materials. of potential nanostructure and fouling transport membrane nous. Furthermore, in Fig. 5, it conformed to the structure structure the to conformed it 5, Fig. in Furthermore, nous. sec cross scattering phonon the materials, nanostructure was prepared the topological surface and measurement the the measurement and surface topological the prepared was rials. The surface roughness is important in evaluating the the evaluating in important is roughness surface The rials. etc) boundaries grain dislocation, defects, (point agents ring roughness value of the pellet surface. As shown Fig. 5, the the 5, Fig. shown As surface. pellet the of value roughness uches the pellet surface and records the small force between force between the small and records surface uches the pellet performance of a membrane as it may influence the trans the influence may it as membrane a of performance parameter was observed through Fig. 6. through AFM not image was observed was parameter als. The electronic parts of these conductivities are linearly linearly are conductivities these of parts electronic The als. supported on a flexible cantilever. The AFM tip gently to gently tip AFM The cantilever. flexible a on supported led that the atom arrangement of the pellet was in homoge in was pellet the of arrangement atom the that led size. crystalline with late scatte bulk other all dominates surfaces rough the of tion o lcrct cneso fco i nnsrcue materi nanostructure in factor conversion electricity to noise. position lowest the for standard the set technology the probe and the pellet surface. The sample in the study study the in sample The surface. pellet the and probe the between 0.2-10 nm probe sample separation. The probe is is probe The separation. sample probe nm 0.2-10 between ideally sharp identification. As a consequence, an AFM ima AFM an a consequence, As identification. sharp ideally [32]. form in crystalline nano in hout effecting very much on the electrical counterpart. In In counterpart. electrical the on much very effecting hout iue 6. Figure Figure 5. - reve studies AFM the 5, Fig. to according addition, In Fig. 6 gives the 3D view of the pellet. The roughness roughness The pellet. the of view 3D the gives 6 Fig. AFM images of Bi of images AFM D F iae n ruhes aaees f Bi of parameters roughness and image AFM 3D 2 Te 3 nanostructure pellet nanostructure 2 Te 3 ------

29 7 AFM is especially recommended for the analyses of such such of analyses the for recommended especially is AFM It was found that variation in surface roughness influences influences roughness surface in variation that found was It FTIR spectrum of the Bi the of spectrum FTIR on with NaBH with on [33]. reports researcher other observation, the average roughness value was about ~68 ~68 about was value roughness average the observation, clarification the organic, polymeric, and in some cases, inor cases, some in and polymeric, organic, the clarification nanostructure surfaces with nano meter size irregularities. irregularities. size meter nano with surfaces nanostructure beca significant were investigation this of results The nm. rum of Bi of rum use large position noise in a nano positioner could obscure obscure could positioner nano a in noise position large use ughness was a crucial data to continue the ability exploring exploring ability the continue to data crucial a was ughness at roughness surface The value. roughness surface upper rus ee lot eue i te ehiu o reducti of technique the in reduced almost were groups ganic materials. The FTIR analysis process uses infrared infrared uses process analysis FTIR The materials. ganic pellet were conformed the nanostructure form according to to form according nanostructure the were conformed pellet ge does not reflect the accurate sample topography, but rat but topography, sample accurate the reflect not does ge functional performance of the TE devices. TE of the performance functional an AFM surface roughness measurement. The nano meter meter nano The measurement. roughness surface AFM an and building TE devices at ever smaller length scales. In this In this scales. length at TE ever devices smaller and building same stretching with the similar bands. In the developed developed the In bands. similar the with stretching same the adjusted was pellet Bi2Te3 the nanostructure servation, size surface roughness value has been strongly influences influences strongly been has value roughness surface size the thermoelectric behaviour of nanostructure materials. materials. nanostructure of behaviour thermoelectric the of the role in determining plays important an scale the nano light to scan the test specimen and investigate the chemical chemical the investigate and specimen test the scan to light (~68 nm). values roughness at low even surface terials ma nanostructure the of characteristics thermoelectric the to C-S, C-H, C-O and O-H stretching vibrations. In this ob this In vibrations. stretching O-H and C-O C-H, C-S, to behaviour of the materials. Fig. 7 illustrates the FT-IR the spect illustrates 7 Fig. materials. the of behaviour in the bands between 400 and 2366 cm 2366 and 400 between bands the in into Bi into her represents the interaction of the probe with the sample sample the with probe the of interaction the represents her Figure 7. The FTIR spectroscopy is an analytical process used to to used process analytical an is spectroscopy FTIR The On the other hand, the oxygen containing functional functional containing oxygen the hand, other the On nesadn ad hrceiig f ao cl ro scale nano of characterizing and Understanding 2 Te FT-IR spectrum of Bi of FT-IR spectrum 2 3 Te nanostructure form.Eventually, nanostructure 3 nanostructure pellet. Expected peak for the the for peak Expected pellet. nanostructure 4 and thus the metal ions were transformed transformed were ions metal the thus and 2 Te 2 Te 3 nanostructure were absorbed absorbed were nanostructure 3 nanostructure pellet nanostructure -1 which correspond correspond which ------

H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299 H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299 ACKNOWLEDGEMENT The pellet was excited by some oxidization and impurity. impurity. and oxidization bysome excited was pellet The This work was supported by the Scientific &Technologi Scientific bythe supported work was This 1. 2221 Fellowship Program, Ref No: 21514107–115.02– Program, 2221 Fellowship CONCLUSION AND FUTURE RESEARCH CONCLUSION FUTURE AND 4. In order to minimize the oxidization, a computer cont a computer oxidization, the minimize order to In It was concluded that by using this method, pure pellets pellets pure method, this byusing that concluded It was Current research activities on Bi on activities research Current E.69236 and Manisa Celal Bayar University Scientific Re Scientific University Bayar Celal Manisa and E.69236 chemical process was employed in terms of financial as of financial terms in employed was process chemical quantum confinement. Size effect was led to carrier con carrier to led was effect Size confinement. quantum developed by using the several processes such as the the as such processes several the by using developed of material was enhanced the thermoelectric power due to due power to thermoelectric the enhanced was of material cal Research Council of Turkey under grant of TUBİTAK of TUBİTAK of Turkey grant under Council Research cal would be produced. Further research recommended that that recommended research Further produced. be would rolled pure H pure rolled reduced. The thermal conductivity was improved more more improved was conductivity thermal The reduced. utilization in thermoelectric applications. thermoelectric in utilization pect and potential for very large quantity of productions. of productions. quantity large for very potential and pect 2. finement. Selective scattering and interface scattering was was scattering interface and scattering Selective finement. solvothermal and hydrothermal. In this paper, the simple paper, simple the this In hydrothermal. and solvothermal grinding, electrochemical, chemical, simple ablation, ser search Projects Coordination Unit, No: 2016–147. Unit, Coordination Projects search thermal evaporation, sputtering, lithographic, pulsed la pulsed lithographic, sputtering, evaporation, thermal than the electrical conductivity; thus the figure of merit was was of merit figure the thus conductivity; electrical the than the pellet to measure the electrical and thermal conduc thermal and electrical the measure to pellet the tivity, Seebeck coefficient and figure of merit for proper of merit figure and coefficient Seebeck tivity, increased. 3. 6. 5. Akshay VR, Suneesh MV, Vasundhara M. Tailoring M. MV, Vasundhara Suneesh VR, Akshay via modified hydrothermal method. Journal of Electronic of Journal method. hydrothermal modified via effects of Bi2Te3 thermoelectric generators for applications 6264–6274. surfactant addition on Bi2Te3 nanostructures synthesized Smith CJW, Cahill JS, Nuhoglu A. Macro to nano: Scaling to nano: Macro A. Nuhoglu JS, Cahill CJW, Smith thermoelectric based Tellurium A. Purohit YC, Sharma morphology in chemically synthesized n-type bismuth n-type synthesized chemically in morphology materials: New directions and prospects. Journal of Journal prospects. and directions New materials: rational structure design. Nanoscale 8(2016) 8681–8686. Nanoscale design. structure rational through nanostructures Bi2Te3-based of performance Integrated Science and Technology 4(2016) 29–32. Technology and Science Integrated telluride nanostructures. Inorganic Chemistry 56 (2017) 56 Chemistry Inorganic nanostructures. telluride thermoelectric properties through structure and Dharmaiah P, Lee C, Madavali B, Hong SJ. Effect of Effect SJ. Hong B, P, Madavali C, Lee Dharmaiah 6(2017) 3012–3019.Materials Bi2Te3 obtained with diverse morphologies nanocrystals of properties Thermoelectric P, SJ. Hong Dharmaiah Hong M, Chen ZG, Yang L, Zou J. Enhancing thermoelectric thermoelectric J.Enhancing Zou L, ZG, Yang Chen M, Hong (2017) 62 1005-1010.Materials in space. 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H. Mamur, M.R.A. Bhuiyan / Hittite J Sci Eng, 2018, 5 (4) 293–299