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Feb 2011

Volume 82, Issue 2, Articles (02xxxx)

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back to top Thermometry; Thermal Diffusivity; Acoustics; Photothermal and Photoacoustic

A self-heating 2ω method for Seebeck coefficient measurement of thermoelectric materials

Tingting Miao, Weigang Ma, Xing Zhang, and Zhen Li

Rev. Sci. Instrum. 82, 024901 (2011); http://dx.doi.org/10.1063/1.3544019 (6 pages) | Cited 2 times

Online Publication Date: 16 February 2011

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A novel and reliable self-heating 2ω method has been developed to measure the Seebeck coefficient of the microscale/nanoscale thermoelectric materials. Based on the analytical solution of the transient heat-conduction equation of the specimen heated by a harmonic current, two measurement modes have been developed: (1) the Seebeck coefficient can be directly extracted from the ratio of experimentally measured 2ω Seebeck voltage to theoretically predicted 2ω temperature drop oscillation; and (2) the Seebeck coefficient can be steadily extracted from the measured 2ω and 3ω voltages. This approach has been applied to a 25.4 μm thick K-type thermocouple and the measured Seebeck coefficient corresponds well with the nominal value.
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07.20.-n Thermal instruments and apparatus
72.15.Jf Thermoelectric and thermomagnetic effects

A noncontact thermal microprobe for local thermal conductivity measurement

Yanliang Zhang, Eduardo E. Castillo, Rutvik J. Mehta, Ganpati Ramanath, and Theodorian Borca-Tasciuc

Rev. Sci. Instrum. 82, 024902 (2011); http://dx.doi.org/10.1063/1.3545823 (4 pages) | Cited 2 times

Online Publication Date: 17 February 2011

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We demonstrate a noncontact thermal microprobe technique for measuring the thermal conductivity κ with ∼3 μm lateral spatial resolution by exploiting quasiballistic air conduction across a 10–100 nm air gap between a joule-heated microprobe and the sample. The thermal conductivity is extracted from the measured effective thermal resistance of the microprobe and the tip–sample thermal contact conductance and radius in the quasiballistic regime determined by calibration on reference samples using a heat transfer model. Our κ values are within 5%–10% of that measured by standard steady-state methods and theoretical predictions for nanostructured bulk and thin film assemblies of pnictogen chalcogenides. Noncontact thermal microprobing demonstrated here mitigates the strong dependence of tip–sample heat transfer on sample surface chemistry and topography inherent in contact methods, and allows the thermal characterization of a wide range of nanomaterials.
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07.20.-n Thermal instruments and apparatus

An integrated microfluidic chip with 40 MHz lead-free transducer for fluid analysis

S. T. F. Lee, K. H. Lam, L. Lei, X. M. Zhang, and H. L. W. Chan

Rev. Sci. Instrum. 82, 024903 (2011); http://dx.doi.org/10.1063/1.3553575 (4 pages)

Online Publication Date: 25 February 2011

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The design, fabrication, and evaluation of a high-frequency transducer made from lead-free piezoceramic for the application of microfluidic analysis is described. Barium strontium zirconate titanate [(Ba0.95Sr0.05)(Zr0.05Ti0.95)O3, abbreviated as BSZT] ceramic has been chosen to be the active element of the transducer. The center frequency and bandwidth of this high-frequency ultrasound transducer have been measured to be 43 MHz and 56.1%, respectively. The transducer was integrated into a microfluidic channel and used to measure the sound velocity and attenuation of the liquid flowing in the channel. Results suggest that lead-free high-frequency transducers could be used for in situ analysis of property of the fluid flowing through the microfluidic system.
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07.07.Mp Transducers
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
06.30.Gv Velocity, acceleration, and rotation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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