This work is directed at the fabrication and optical characterization of anisotropic semiconductor composites with improved thermoelectric properties. Specifically, the quest is to dramatically improve the thermoelectric figure-of-merit, ZT, with an emphasis on the effects of "nanoconfinement", and on the crystallographic properties which provide an increase in the electrical-to-thermal conductivity ratio. Current work entails the fabrication of force-oriented nanostructural confinement of Bismuth (Bi) and Bismuth Telluride (Bi/sub 2/Te/sub 3/).
{"title":"Dense semiconductor-insulator nanocomposites for navy thermoelectric applications","authors":"D. Demske","doi":"10.1109/ICT.1996.553514","DOIUrl":"https://doi.org/10.1109/ICT.1996.553514","url":null,"abstract":"This work is directed at the fabrication and optical characterization of anisotropic semiconductor composites with improved thermoelectric properties. Specifically, the quest is to dramatically improve the thermoelectric figure-of-merit, ZT, with an emphasis on the effects of \"nanoconfinement\", and on the crystallographic properties which provide an increase in the electrical-to-thermal conductivity ratio. Current work entails the fabrication of force-oriented nanostructural confinement of Bismuth (Bi) and Bismuth Telluride (Bi/sub 2/Te/sub 3/).","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125886888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent awareness of the transport properties of Skutterudite pnictides has stimulated an interest in numerous other intermetallic compounds having a gap in the density of states at the Fermi level including the MNiSn compounds where M=(Ti, Zr, Hf). These intermetallic 'half-Heusler' compounds are characterized by high Seebeck coefficients (-150 to -300 /spl mu/V/deg.) and reasonable carrier mobilities (30 to 50 cm/sup 2//V-s) at room temperature which make them attractive candidates for intermediate temperature thermoelectric applications. Samples of TiNiSn were prepared by arc melting and homogenized by heat treatment. The temperature dependence of the electrical resistivity, Seebeck coefficient, and thermal diffusivity of these samples was characterized between 22/spl deg/C and 900/spl deg/C. The electrical resistivity and thermopower both decrease with temperature although the resistivity decreases at a faster rate. Electrical power factors in excess of 25 /spl mu/W/cm-/spl deg/C/sup 2/ were observed in nearly single phase alloys within a 300 to 600/spl deg/C temperature range. A brief survey of other selected ternary intermetallic compounds is also presented.
{"title":"TiNiSn: a gateway to the (1,1,1) intermetallic compounds","authors":"B. Cook, J. Harringa, Z. Tan, W. Jesser","doi":"10.2172/244657","DOIUrl":"https://doi.org/10.2172/244657","url":null,"abstract":"Recent awareness of the transport properties of Skutterudite pnictides has stimulated an interest in numerous other intermetallic compounds having a gap in the density of states at the Fermi level including the MNiSn compounds where M=(Ti, Zr, Hf). These intermetallic 'half-Heusler' compounds are characterized by high Seebeck coefficients (-150 to -300 /spl mu/V/deg.) and reasonable carrier mobilities (30 to 50 cm/sup 2//V-s) at room temperature which make them attractive candidates for intermediate temperature thermoelectric applications. Samples of TiNiSn were prepared by arc melting and homogenized by heat treatment. The temperature dependence of the electrical resistivity, Seebeck coefficient, and thermal diffusivity of these samples was characterized between 22/spl deg/C and 900/spl deg/C. The electrical resistivity and thermopower both decrease with temperature although the resistivity decreases at a faster rate. Electrical power factors in excess of 25 /spl mu/W/cm-/spl deg/C/sup 2/ were observed in nearly single phase alloys within a 300 to 600/spl deg/C temperature range. A brief survey of other selected ternary intermetallic compounds is also presented.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126127101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reactive precursors M(NMe/sub 2/)/sub 3/ (M=Sb, Bi) and (Me/sub 1/Si)/sub 2/Te were used to deposit films of M/sub 2/Te/sub 3/ (M=Sb, Bi) on Si(111) cut 4/spl deg/ off-axis, GaAs(100), and Kapton substrates between 25/spl deg/C and 150/spl deg/C in a low pressure MOCVD reactor. The film growth process is a novel N,N-dimethylamino-trimethylsilane (Me/sub 3/SiNMe/sub 2/) elimination reaction and not pyrolysis reactions employed in conventional MOCVD techniques. X-ray diffraction data show the crystalline quality and orientation of the resulting polycrystalline films were dependent on the substrate structure and growth temperature. Amorphous films were deposited below 50/spl deg/C. Films deposited at 75/spl deg/C for Sb/sub 2/Te/sub 3/ and 125/spl deg/C for Bi/sub 2/Te/sub 3/ were highly oriented with the (015) reflection plane parallel to the substrate surface. Films of Sb/sub 2/Te/sub 3/ deposited at 150/spl deg/C were highly oriented with the [00l] reflection planes parallel to the substrate surface. The electrical properties and composition of Bi/sub 2/Te/sub 3/ films deposited at 125/spl deg/C on Kapton were independent of the V/VI precursor ratio used. Variation in the composition of a Sb/sub x/Bi/sub 2-x/Te/sub 3/ ternary film across the susceptor was observed due to differences in the reaction kinetics for formation of Sb/sub 2/Te/sub 3/ and Bi/sub 2/Te/sub 3/. This unique deposition reaction provides an alternative route to prepare group V chalcogenide materials which have potential applications in solar cells, reversible optical storage, and thermoelectrics.
{"title":"Low temperature MOCVD growth of V/VI materials via a Me3SiNMe2 elimination reaction","authors":"T. Groshens, R. Gedridge, R. Scheri, T. Cole","doi":"10.1109/ICT.1996.553521","DOIUrl":"https://doi.org/10.1109/ICT.1996.553521","url":null,"abstract":"The reactive precursors M(NMe/sub 2/)/sub 3/ (M=Sb, Bi) and (Me/sub 1/Si)/sub 2/Te were used to deposit films of M/sub 2/Te/sub 3/ (M=Sb, Bi) on Si(111) cut 4/spl deg/ off-axis, GaAs(100), and Kapton substrates between 25/spl deg/C and 150/spl deg/C in a low pressure MOCVD reactor. The film growth process is a novel N,N-dimethylamino-trimethylsilane (Me/sub 3/SiNMe/sub 2/) elimination reaction and not pyrolysis reactions employed in conventional MOCVD techniques. X-ray diffraction data show the crystalline quality and orientation of the resulting polycrystalline films were dependent on the substrate structure and growth temperature. Amorphous films were deposited below 50/spl deg/C. Films deposited at 75/spl deg/C for Sb/sub 2/Te/sub 3/ and 125/spl deg/C for Bi/sub 2/Te/sub 3/ were highly oriented with the (015) reflection plane parallel to the substrate surface. Films of Sb/sub 2/Te/sub 3/ deposited at 150/spl deg/C were highly oriented with the [00l] reflection planes parallel to the substrate surface. The electrical properties and composition of Bi/sub 2/Te/sub 3/ films deposited at 125/spl deg/C on Kapton were independent of the V/VI precursor ratio used. Variation in the composition of a Sb/sub x/Bi/sub 2-x/Te/sub 3/ ternary film across the susceptor was observed due to differences in the reaction kinetics for formation of Sb/sub 2/Te/sub 3/ and Bi/sub 2/Te/sub 3/. This unique deposition reaction provides an alternative route to prepare group V chalcogenide materials which have potential applications in solar cells, reversible optical storage, and thermoelectrics.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127428520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The thermal conductivity of polycrystalline sintered BiSb has been measured from 80 to 300 K. The samples had mean grain sizes between 1 /spl mu/m and 19 /spl mu/m. The electronic contribution to the thermal conductivity was determined by a technique that involves the comparison of the magneto-resistance and the magneto-thermal resistance effects in transverse fields of up to 1.0 tesla. The electronic thermal conductivity seems to be somewhat smaller than expected, bearing in mind that there should be a significant bipolar contribution, yet the technique is believed to be sound since it yields a lattice thermal conductivity for large-grained samples that is intermediate between the values for single crystals in the principal crystal directions. The lattice thermal conductivity is found to decrease as the grain size is reduced. Such a decrease has been predicted on the basis of grain boundary scattering of phonons but it is occurring at grain sizes somewhat larger than expected. It is possible that the effect may be due to the scattering of phonons on point or line defects that have been introduced as a consequence of powder metallurgy. Nevertheless, grain boundary scattering cannot be ruled out as the cause, in view of the simplifications that were made in the theory.
{"title":"Observation of the effect of grain size on the lattice thermal conductivity of polycrystalline bismuth antimony","authors":"E. H. Volckmann, H. Goldsmid, J. Sharp","doi":"10.1109/ICT.1996.553249","DOIUrl":"https://doi.org/10.1109/ICT.1996.553249","url":null,"abstract":"The thermal conductivity of polycrystalline sintered BiSb has been measured from 80 to 300 K. The samples had mean grain sizes between 1 /spl mu/m and 19 /spl mu/m. The electronic contribution to the thermal conductivity was determined by a technique that involves the comparison of the magneto-resistance and the magneto-thermal resistance effects in transverse fields of up to 1.0 tesla. The electronic thermal conductivity seems to be somewhat smaller than expected, bearing in mind that there should be a significant bipolar contribution, yet the technique is believed to be sound since it yields a lattice thermal conductivity for large-grained samples that is intermediate between the values for single crystals in the principal crystal directions. The lattice thermal conductivity is found to decrease as the grain size is reduced. Such a decrease has been predicted on the basis of grain boundary scattering of phonons but it is occurring at grain sizes somewhat larger than expected. It is possible that the effect may be due to the scattering of phonons on point or line defects that have been introduced as a consequence of powder metallurgy. Nevertheless, grain boundary scattering cannot be ruled out as the cause, in view of the simplifications that were made in the theory.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127713829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The range of existence of the homogeneous /spl delta/-phase of (Bi/sub 0.5/Sb/sub 0.5/)/sub 2/Te/sub 3/ in the phase diagram (Bi,Sb)-Te intersects the stoichiometry line. n-type samples can be obtained by Bridgman growth with excess of tellurium. Due to the strong tellurium segregation the transition from the p-extrinsic region through intrinsic material to n-extrinsic behavior proceeds within a sample section of several millimeters along the axial direction. The positive and negative maximum values S/sub max.p/ and S/sub max.n/ can be read out from a scan of the Seebeck coefficient by the micro-thermoprobe technique over the transition area. The p-type maximum scan value is in good agreement with the value deduced from the integral measurement of homogeneous bulk samples. The width of the thermal band gap and the ratio of the electronic parameters /spl mu//sub B/(m/sub d//m/sub o/)/sup 3/2/ (/spl mu//sub B/-non-degeneracy value of the carrier mobility (reduced to Boltzmann statistics); m/sub d//m/sub o/-reduced d.o.s. mass) of holes and electrons are obtained from S/sub max.p/ and S/sub max.n/. The mobility of holes as minority carriers exhibits a strong sensitivity on doping impurities.
{"title":"Determination of the thermal band gap from the change of the Seebeck-coefficient at the pn-transition in (Bi0.5Sb0.5)2)Te3","authors":"E. Muller, W. Heiliger, P. Reinshaus, H. Submann","doi":"10.1109/ICT.1996.553517","DOIUrl":"https://doi.org/10.1109/ICT.1996.553517","url":null,"abstract":"The range of existence of the homogeneous /spl delta/-phase of (Bi/sub 0.5/Sb/sub 0.5/)/sub 2/Te/sub 3/ in the phase diagram (Bi,Sb)-Te intersects the stoichiometry line. n-type samples can be obtained by Bridgman growth with excess of tellurium. Due to the strong tellurium segregation the transition from the p-extrinsic region through intrinsic material to n-extrinsic behavior proceeds within a sample section of several millimeters along the axial direction. The positive and negative maximum values S/sub max.p/ and S/sub max.n/ can be read out from a scan of the Seebeck coefficient by the micro-thermoprobe technique over the transition area. The p-type maximum scan value is in good agreement with the value deduced from the integral measurement of homogeneous bulk samples. The width of the thermal band gap and the ratio of the electronic parameters /spl mu//sub B/(m/sub d//m/sub o/)/sup 3/2/ (/spl mu//sub B/-non-degeneracy value of the carrier mobility (reduced to Boltzmann statistics); m/sub d//m/sub o/-reduced d.o.s. mass) of holes and electrons are obtained from S/sub max.p/ and S/sub max.n/. The mobility of holes as minority carriers exhibits a strong sensitivity on doping impurities.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128027889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Venkatasubramanian, T. Colpitts, E. Watko, J. Hutchby
Thermoelectric properties of p-type Bi/sub 2/Te/sub 3//Sb/sub 2/Te/sub 3/ superlattice (SL) thin-films grown by organometallic vapor phase epitaxy (OMVPE) are described. The electrical and thermal transport properties including, hole mobility, Seebeck coefficient and power factor as a function of SL dimension are described. It is observed that the carrier mobility, Seebeck coefficient and power factor of the Bi/sub 2/Te/sub 3//Sb/sub 2/Te/sub 3/ SL structures are better than that of p-type Bi/sub x/Sb/sub 2-x/Te/sub 3/ alloys, with similar bandgap and electrical resistivity. The improvement in carrier mobility is attributed to avoiding or minimizing alloy scattering of carriers with SL structures while the enhanced Seebeck coefficient is related to the bandstructure difference between the alloy and the SL structures. Initial measurements indicate that power factor improvement of /spl sim/50%, over corresponding alloys, can be obtained in SL structures. We have measured the thermal conductivity of the SL structures by the 3-/spl omega/ method and have observed a factor of four to seven reduction in thermal conductivity of optimized structures, with respect to the alloys. The electrical conductivity and Seebeck coefficient are measured in the plane of the SL structures, while the 3-/spl omega/-measured thermal conductivity can potentially be dominated by a component perpendicular to the SL structures. Hence, the figure-of-merit (ZT) values are estimated with a correction for potential anisotropy of thermal conductivity. Including this correction, implying higher assumed thermal conductivities in the plane of SL's, the preliminary estimated ZT for some SL structures are in the range of 1.22 to 1.67 at 300 K.
{"title":"Experimental evidence of high power factors and low thermal conductivity in Bi2Te3/Sb2Te3 superlattice thin-films","authors":"R. Venkatasubramanian, T. Colpitts, E. Watko, J. Hutchby","doi":"10.1109/ICT.1996.553526","DOIUrl":"https://doi.org/10.1109/ICT.1996.553526","url":null,"abstract":"Thermoelectric properties of p-type Bi/sub 2/Te/sub 3//Sb/sub 2/Te/sub 3/ superlattice (SL) thin-films grown by organometallic vapor phase epitaxy (OMVPE) are described. The electrical and thermal transport properties including, hole mobility, Seebeck coefficient and power factor as a function of SL dimension are described. It is observed that the carrier mobility, Seebeck coefficient and power factor of the Bi/sub 2/Te/sub 3//Sb/sub 2/Te/sub 3/ SL structures are better than that of p-type Bi/sub x/Sb/sub 2-x/Te/sub 3/ alloys, with similar bandgap and electrical resistivity. The improvement in carrier mobility is attributed to avoiding or minimizing alloy scattering of carriers with SL structures while the enhanced Seebeck coefficient is related to the bandstructure difference between the alloy and the SL structures. Initial measurements indicate that power factor improvement of /spl sim/50%, over corresponding alloys, can be obtained in SL structures. We have measured the thermal conductivity of the SL structures by the 3-/spl omega/ method and have observed a factor of four to seven reduction in thermal conductivity of optimized structures, with respect to the alloys. The electrical conductivity and Seebeck coefficient are measured in the plane of the SL structures, while the 3-/spl omega/-measured thermal conductivity can potentially be dominated by a component perpendicular to the SL structures. Hence, the figure-of-merit (ZT) values are estimated with a correction for potential anisotropy of thermal conductivity. Including this correction, implying higher assumed thermal conductivities in the plane of SL's, the preliminary estimated ZT for some SL structures are in the range of 1.22 to 1.67 at 300 K.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121078575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polycrystalline SiGe films have applications in solar cells, thermoelectrical devices and field-effect transistors for large area integration (liquid crystal displays etc.). Recently, a nanocrystalline state was detected by us in heavily B-doped SiGe films after vacuum annealing. Amorphous (a) Si/sub 1-x/Ge/sub x/ films with x=0.25-0.60, about 200-300 nm thick and heavily doped with Ga (1%), were deposited by molecular beam on SiO/sub 2//Si[001] substrates at room temperature. For crystallization, a-SiGe/SiO/sub 2//Si structures were annealed in vacuum of 10/sup -6/ Torr at 600 to 900/spl deg/C. X-ray diffraction and TEM observations in situ showed nanocrystalline (nc) structure in SiGe films with grain size of about 5-20 nm. The nc-Si/sub 1-x/Ge/sub x/ films demonstrated high hole mobility (1 to 100 cm/sup 2//Vs) and Seebeck coefficient values (5 to 110 /spl mu/V/K).
{"title":"Structure and transport properties of Ga-doped semi- and polycrystalline Si/sub 1-x/Gex films","authors":"F. Edelman, M. Stolzer, P. Werner, R. Butz","doi":"10.1109/ICT.1996.553530","DOIUrl":"https://doi.org/10.1109/ICT.1996.553530","url":null,"abstract":"Polycrystalline SiGe films have applications in solar cells, thermoelectrical devices and field-effect transistors for large area integration (liquid crystal displays etc.). Recently, a nanocrystalline state was detected by us in heavily B-doped SiGe films after vacuum annealing. Amorphous (a) Si/sub 1-x/Ge/sub x/ films with x=0.25-0.60, about 200-300 nm thick and heavily doped with Ga (1%), were deposited by molecular beam on SiO/sub 2//Si[001] substrates at room temperature. For crystallization, a-SiGe/SiO/sub 2//Si structures were annealed in vacuum of 10/sup -6/ Torr at 600 to 900/spl deg/C. X-ray diffraction and TEM observations in situ showed nanocrystalline (nc) structure in SiGe films with grain size of about 5-20 nm. The nc-Si/sub 1-x/Ge/sub x/ films demonstrated high hole mobility (1 to 100 cm/sup 2//Vs) and Seebeck coefficient values (5 to 110 /spl mu/V/K).","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124515019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optimum configuration, assembling and commutation of the cells in a thermoelectric device have been investigated taking into account the temperature dependence of resistivity, thermal conductivity and Seebeck coefficient of the material operating at the large temperature drop. A solution is proposed which enables one to increase the effective figure of merit of the device as compared to the mean value of Z measured at the same temperature drop in a single wafer thermoelectric cell.
{"title":"Effective figure of merit increase at the large temperature drops","authors":"V. Yurchenko","doi":"10.1109/ICT.1996.553293","DOIUrl":"https://doi.org/10.1109/ICT.1996.553293","url":null,"abstract":"Optimum configuration, assembling and commutation of the cells in a thermoelectric device have been investigated taking into account the temperature dependence of resistivity, thermal conductivity and Seebeck coefficient of the material operating at the large temperature drop. A solution is proposed which enables one to increase the effective figure of merit of the device as compared to the mean value of Z measured at the same temperature drop in a single wafer thermoelectric cell.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114263152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Miyajima, K. Takagi, H. Okamura, Gil-Geun Lee, Y. Noda, R. Watanabe
To study the mechanical alloying process and the properties of thermoelectric semiconductor with fine dispersed ceramic particles, Bi-Sb alloys with addition of fine BN and ZrO/sub 2/ were prepared by mechanical alloying. The milled powders were sintered by hot pressing. The Bi/sub 92.5/Sb/sub 7.5/ solid solution with fine dispersion of BN and ZrO ceramic particles were successfully synthesized. The sintered composites show very fine microstructures in which average grain size are less than one micron. The thermal properties of composites were measured by laser flash method at room temperature. The electrical properties were measured by Van der Pauw method at room temperature and at 77 K. The BN addition has obtained larger reduction of thermal conductivity compared to ZrO/sub 2/. The thermal conductivity has been reduced to 20% of the reported value of Bi-Sb single crystal, which achieved with 10 vol% addition of BN.
{"title":"Thermoelectric properties of Bi-Sb composite prepared by mechanical alloying method","authors":"M. Miyajima, K. Takagi, H. Okamura, Gil-Geun Lee, Y. Noda, R. Watanabe","doi":"10.1109/ICT.1996.553248","DOIUrl":"https://doi.org/10.1109/ICT.1996.553248","url":null,"abstract":"To study the mechanical alloying process and the properties of thermoelectric semiconductor with fine dispersed ceramic particles, Bi-Sb alloys with addition of fine BN and ZrO/sub 2/ were prepared by mechanical alloying. The milled powders were sintered by hot pressing. The Bi/sub 92.5/Sb/sub 7.5/ solid solution with fine dispersion of BN and ZrO ceramic particles were successfully synthesized. The sintered composites show very fine microstructures in which average grain size are less than one micron. The thermal properties of composites were measured by laser flash method at room temperature. The electrical properties were measured by Van der Pauw method at room temperature and at 77 K. The BN addition has obtained larger reduction of thermal conductivity compared to ZrO/sub 2/. The thermal conductivity has been reduced to 20% of the reported value of Bi-Sb single crystal, which achieved with 10 vol% addition of BN.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131658136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. V. Wagner, R. Foreman, L. Summers, T. Barbee, J. Farmer
The deposition of compositionally-modulated (Bi/sub 1-x/Sb/sub x/)/sub 2/(Te/sub 1-y/Se/sub y/)/sub 3/ thermoelectric multilayer films by magnetron sputtering has been demonstrated. Structures with a period of 140 /spl Aring/ are shown to be stable to interdiffusion at the high deposition temperatures necessary for growth of single-layer crystalline films with ZT>0.5. These multilayers are of the correct dimension to exhibit the electronic properties of quantum well structures. Furthermore it is shown that the Seebeck coefficient of the films is not degraded by the presence of this multilayer structure. It may be possible to synthesize a multilayer thermoelectric material with enhanced ZT by maximizing the barrier height through optimization of the composition of the barrier.
{"title":"Synthesis and evaluation of thermoelectric multilayer films","authors":"A. V. Wagner, R. Foreman, L. Summers, T. Barbee, J. Farmer","doi":"10.1109/ICT.1996.553527","DOIUrl":"https://doi.org/10.1109/ICT.1996.553527","url":null,"abstract":"The deposition of compositionally-modulated (Bi/sub 1-x/Sb/sub x/)/sub 2/(Te/sub 1-y/Se/sub y/)/sub 3/ thermoelectric multilayer films by magnetron sputtering has been demonstrated. Structures with a period of 140 /spl Aring/ are shown to be stable to interdiffusion at the high deposition temperatures necessary for growth of single-layer crystalline films with ZT>0.5. These multilayers are of the correct dimension to exhibit the electronic properties of quantum well structures. Furthermore it is shown that the Seebeck coefficient of the films is not degraded by the presence of this multilayer structure. It may be possible to synthesize a multilayer thermoelectric material with enhanced ZT by maximizing the barrier height through optimization of the composition of the barrier.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128574964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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