The Experts below are selected from a list of 17430 Experts worldwide ranked by ideXlab platform
Joshua Martin - One of the best experts on this subject based on the ideXlab platform.
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thermocyclic stability of candidate Seebeck Coefficient standard reference materials at high temperature
Journal of Applied Physics, 2014Co-Authors: Joshua Martin, W Wongng, Thierry Caillat, I Yonenaga, M L GreenAbstract:The Seebeck Coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck Coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs®) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck Coefficient measurement equipment, NIST certified SRM® 3451 “Low Temperature Seebeck Coefficient Standard (10 K to 390 K)”. Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300 K to 900 K). The principal requirement of a SR...
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protocols for the high temperature measurement of the Seebeck Coefficient in thermoelectric materials
Measurement Science and Technology, 2013Co-Authors: Joshua MartinAbstract:In Seebeck Coefficient metrology, the present diversity in apparatus design, acquisition methodology and contact geometry has resulted in conflicting materials data that complicate the interlaboratory confirmation of reported high efficiency thermoelectric materials. To elucidate the influence of these factors in the measurement of the Seebeck Coefficient at high temperature and to identify optimal metrology protocols, we measure the Seebeck Coefficient as a function of contact geometry under both steady-state and transient thermal conditions of the differential method, using a custom developed apparatus capable of in situ comparative measurement. The thermal gradient formation and data acquisition methodology, under ideal conditions, have little effect on the measured Seebeck Coefficient value. However, the off-axis 4-probe contact geometry, as compared to the 2-probe, results in a greater local temperature measurement error that increases with temperature. For surface temperature measurement, the dominant thermal errors arise from a parasitic heat flux that is dependent on the temperature difference between the sample and the external thermal environment, and on the various thermal resistances. Due to higher macroconstriction and contact resistance in the 4-probe arrangement, the measurement of surface temperature for this contact geometry exhibits greater error, thereby overestimating the Seebeck Coefficient.
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error modeling of Seebeck Coefficient measurements using finite element analysis
Journal of Electronic Materials, 2013Co-Authors: Joshua MartinAbstract:Using finite-element analysis, we have developed a metrology simulation to model errors in the measurement of the Seebeck Coefficient. This physical parameter is the constant of proportionality relating the electric potential generated across a conductor to the applied thermal gradient. Its measurement requires careful attention to the electrical and thermal contact interfaces. Furthermore, it is essential that the electric potential and temperature difference be acquired at the same time and at the same location. We have performed Seebeck Coefficient measurement simulations to quantitatively explore the effect of temporal perturbation to the voltage and temperature correspondence, by comparing simultaneous and staggered data acquisition techniques under the quasi-steady-state condition. Using a similar method, we have developed an error model to explore the effect of misalignment between the voltage and temperature probes on the measurement of the Seebeck Coefficient. This approach enables the exploration of experimentally inaccessible data spaces under ideal conditions.
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apparatus for the high temperature measurement of the Seebeck Coefficient in thermoelectric materials
Review of Scientific Instruments, 2012Co-Authors: Joshua MartinAbstract:The Seebeck Coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck Coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck Coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck Coefficient under multiple conditions and probe arrangements (300 K–1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck Coefficient measurements.
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is essential for interlaboratory data comparison and for instrument calibration. Certification measurements were performed using a differential steady-state technique on 10 samples (15 measurements) randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K, and they are further supported by transient measurements. The availability of this SRM will validate measurement results, leading to a better understanding of the structure/property relationships and underlying physics of potential high-efficiency thermoelectric materials.
M L Green - One of the best experts on this subject based on the ideXlab platform.
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thermocyclic stability of candidate Seebeck Coefficient standard reference materials at high temperature
Journal of Applied Physics, 2014Co-Authors: Joshua Martin, W Wongng, Thierry Caillat, I Yonenaga, M L GreenAbstract:The Seebeck Coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck Coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs®) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck Coefficient measurement equipment, NIST certified SRM® 3451 “Low Temperature Seebeck Coefficient Standard (10 K to 390 K)”. Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300 K to 900 K). The principal requirement of a SR...
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is essential for interlaboratory data comparison and for instrument calibration. Certification measurements were performed using a differential steady-state technique on 10 samples (15 measurements) randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K, and they are further supported by transient measurements. The availability of this SRM will validate measurement results, leading to a better understanding of the structure/property relationships and underlying physics of potential high-efficiency thermoelectric materials.
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is crucial for inter-laboratory data comparison and for instrument calibration. Certification measurements were performed using two different techniques on 10 samples randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K. The availability of this SRM will validate the measurement accuracy, leading to a better understanding of the structure/property relationships, and the underlying physics of new and improved thermoelectric materials. An overview of the measurement techniques and data analysis is given.
Jeff Sharp - One of the best experts on this subject based on the ideXlab platform.
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is essential for interlaboratory data comparison and for instrument calibration. Certification measurements were performed using a differential steady-state technique on 10 samples (15 measurements) randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K, and they are further supported by transient measurements. The availability of this SRM will validate measurement results, leading to a better understanding of the structure/property relationships and underlying physics of potential high-efficiency thermoelectric materials.
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is crucial for inter-laboratory data comparison and for instrument calibration. Certification measurements were performed using two different techniques on 10 samples randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K. The availability of this SRM will validate the measurement accuracy, leading to a better understanding of the structure/property relationships, and the underlying physics of new and improved thermoelectric materials. An overview of the measurement techniques and data analysis is given.
W Wongng - One of the best experts on this subject based on the ideXlab platform.
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thermocyclic stability of candidate Seebeck Coefficient standard reference materials at high temperature
Journal of Applied Physics, 2014Co-Authors: Joshua Martin, W Wongng, Thierry Caillat, I Yonenaga, M L GreenAbstract:The Seebeck Coefficient is the most widely measured property specific to thermoelectric materials. There is currently no consensus on measurement protocols, and researchers employ a variety of techniques to measure the Seebeck Coefficient. The implementation of standardized measurement protocols and the use of reliable Seebeck Coefficient Standard Reference Materials (SRMs®) will allow the accurate interlaboratory comparison and validation of materials data, thereby accelerating the development and commercialization of more efficient thermoelectric materials and devices. To enable members of the thermoelectric materials community the means to calibrate Seebeck Coefficient measurement equipment, NIST certified SRM® 3451 “Low Temperature Seebeck Coefficient Standard (10 K to 390 K)”. Due to different practical requirements in instrumentation, sample contact methodology, and thermal stability, a complementary SRM® is required for the high temperature regime (300 K to 900 K). The principal requirement of a SR...
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is essential for interlaboratory data comparison and for instrument calibration. Certification measurements were performed using a differential steady-state technique on 10 samples (15 measurements) randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K, and they are further supported by transient measurements. The availability of this SRM will validate measurement results, leading to a better understanding of the structure/property relationships and underlying physics of potential high-efficiency thermoelectric materials.
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development of a Seebeck Coefficient standard reference material
Journal of Materials Research, 2011Co-Authors: Nathan D Lowhorn, Joshua Martin, W Wongng, M L Green, John E Bonevich, E L Thomas, N Dilley, Jeff SharpAbstract:We have successfully developed a Seebeck Coefficient Standard Reference Material (SRM™), Bi2Te3, that is crucial for inter-laboratory data comparison and for instrument calibration. Certification measurements were performed using two different techniques on 10 samples randomly selected from a batch of 390 bars. The certified Seebeck Coefficient values are provided from 10 to 390 K. The availability of this SRM will validate the measurement accuracy, leading to a better understanding of the structure/property relationships, and the underlying physics of new and improved thermoelectric materials. An overview of the measurement techniques and data analysis is given.
A C Gossard - One of the best experts on this subject based on the ideXlab platform.
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cross plane Seebeck Coefficient and lorenz number in superlattices
Physical Review B, 2007Co-Authors: Zhixi Bian, Mona Zebarjadi, Rashmi Singh, Younes Ezzahri, Ali Shakouri, Gehong Zeng, Jehyeong Bahk, J E Bowers, Joshua M O Zide, A C GossardAbstract:Low dimensional and nanostructured materials have shown great potential to achieve much higher thermoelectric figure of merits than their bulk counterparts. Here, we study the thermoelectric properties of superlattices in the cross-plane direction using the Boltzmann transport equation and taking into account multiple minibands. Poisson equation is solved self-consistently to include the effect of charge transfer and band bending in the potential profile. The model is verified with the experimental data of cross-plane Seebeck Coefficient for a superlattice structure with different doping concentrations. The simulations show that thermoelectric properties of superlattices are quite different from those of bulk materials because the electronic band structure is modified by the periodic potential. The Lorenz numbers of superlattices are surprisingly large at low carrier concentrations and deviate far away from the Wiedemann-Franz law for bulk materials. Under some conditions, the Lorenz number could be reduced by 50% compared to the bulk value. Most significantly, the Seebeck Coefficient and the Lorenz number of superlattices do not change monotonically with doping concentration. An oscillatory behavior is observed. The effects of temperature and well and barrier thicknesses on the cross-plane Seebeck Coefficient and Lorenz number are also investigated.
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cross plane Seebeck Coefficient of eras ingaas ingaalas superlattices
Journal of Applied Physics, 2007Co-Authors: Gehong Zeng, Zhixi Bian, Ali Shakouri, J E Bowers, Joshua M O Zide, A C Gossard, Woochul Kim, Yan Zhang, Suzanne L Singer, Arun MajumdarAbstract:We characterize cross-plane and in-plane Seebeck Coefficients for ErAs:InGaAs∕InGaAlAs superlattices with different carrier concentrations using test patterns integrated with microheaters. The microheater creates a local temperature difference, and the cross-plane Seebeck Coefficients of the superlattices are determined by a combination of experimental measurements and finite element simulations. The cross-plane Seebeck Coefficients are compared to the in-plane Seebeck Coefficients and a significant increase in the cross-plane Seebeck Coefficient over the in-plane Seebeck Coefficient is observed. Differences between cross-plane and in-plane Seebeck Coefficients decrease as the carrier concentration increases, which is indicative of heterostructure thermionic emission in the cross-plane direction.
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demonstration of electron filtering to increase the Seebeck Coefficient in in 0 53 ga 0 47 as in 0 53 ga 0 28 al 0 19 as superlattices
Physical Review B, 2006Co-Authors: Joshua M O Zide, Zhixi Bian, Ali Shakouri, Gehong Zeng, J E Bowers, Daryoosh Vashaee, A C GossardAbstract:In this paper, we explore electron filtering as a technique to increase the Seebeck Coefficient and the thermoelectric power factor of heterostructured materials over that of the bulk. We present a theoretical model in which the Seebeck Coefficient and the power factor can be increased in an ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$-based composite material. Experimental measurements of the cross-plane Seebeck Coefficient are presented and confirm the importance of the electron filtering technique to decouple the electrical conductivity and Seebeck Coefficient to increase the thermoelectric power factor.
