Realizing high thermoelectric performance in p-type RbZn4P3 Zintl compound: a first-principles investigation

Journal of Materials Science - This work presents structural, elastic, electronic, and thermoelectric properties of a tetragonal Zintl compound RbZn4P3, using the Density Functional Theory and...     

Microstructure and thermoelectric properties of p-type Bi-Sb-Te-Se thin films prepared by electrodeposition method

P-type Bi-Sb-Te-Se thermoelectric thin films with thickness of 8 μm have been prepared by cathodic electrodeposition technique on Au substrate from nitric acid solution system at room temperature. Cyclic voltammetry was used for determination of the deposition potentials of the thin films. In order to enhance the crystallinity, as well as the thermoelectric properties of the deposited films, they were annealed at 523 K for 2 h under nitrogen atmospheric pressure condition. X-ray diffraction (XRD), environmental scanning electron microscopy, and energy-dispersive spectroscopy (EDS) were employed to characterize the thin films. Seebeck coefficients and resistivities of the films were also evaluated. The results revealed that Bi, Sb, Te and Se could be co-deposited to form Bi-Sb-Te-Se semiconductor compound in the solution containing Bi^III, Sb^III, Te^IV and Se^IV and the compositions of the films were sensitive to the electrodepositing potentials. The XRD results suggested that the crystal structure of the thin films were changed from amorphous state to polycrystalline after annealing. The EDS data indicated that the composition of the films was consistent with XRD results. The annealed Bi-Sb-Te-Se thin films exhibited the Seebeck coefficients of 116-133 μV/K and a maximum power factor of 0.62 mW·K^− 2·m^− 1.     

Instability-induced wrinkling in thermoelectric thin film/substrate structures for thermal protection systems in supersonic space shuttle applications

ABSTRACT

This paper examines the behavior of wrinkling instability of a thermoelectric thin film bonded to substrate. The critical temperature differences for wrinkling occurrence and buckling initiation are obtained. Damage growth following wrinkling is also determined. These critical temperatures can provide guidelines for the design of thermoelectric thin film devices. Numerical results show that the stability of thermoelectric thin film is affected by the electric current. The critical temperature differences become smaller when the electric current density in thermoelectric thin film is higher. Effect of the wavelength of wrinkling on the critical temperature differences of wrinkling occurrence is also identified.     

Enhanced thermoelectric figure-of-merit in p-type nanostructured bismuth antimony tellurium alloys made from elemental chunks

By ball milling alloyed bulk crystalline ingots into nanopowders and hot pressing them, we had demonstrated high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this study, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 in the temperature range of 75 and 100 degrees C has been achieved. This process is more economical and environmentally friendly than starting from alloyed bulk crystalline ingots. The ZT improvement is caused mostly by the lower thermal conductivity, similar as the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the increased grain boundaries of the nanograins, precipitates, nanodots, and defects. Our material also exhibits a ZT of 0.7 at 250 degrees C, similar to the value obtained when ingot was used. This study demonstrates that high ZT values can be achieved in nanostructured bulk materials with ball milling elemental chunks, suggesting that the approach can be applied to other materials that are hard to be made into ingot, in addition to its advantage of lower manufacturing cost.     

Design principle of telluride-based nanowire heterostructures for potential thermoelectric applications

We present a design principle to develop new categories of telluride-based thermoelectric nanowire heterostructures through rational solution-phase reactions. The catalyst-free synthesis yields Te-Bi(2)Te(3) "barbell" nanowire heterostructures with a narrow diameter and length distribution as well as a rough control over the density of the hexagonal Bi(2)Te(3) plates on the Te nanowire bodies, which can be further converted to other telluride-based compositional-modulated nanowire heterostructures such as PbTe-Bi(2)Te(3). Initial characterizations of the hot-pressed nanostructured bulk pellets of the Te-Bi(2)Te(3) heterostructure show a largely enhanced Seebeck coefficient and greatly reduced thermal conductivity, which lead to an improved thermoelectric figure of merit. This approach opens up new platforms to investigate the phonon scattering and energy filtering.     

Piezotensegritic structures for transducer applications

Piezoelectricity and tensegrity have been coupled into an electrically active device. This concept, hereby known as piezotensegrity, can be used to sense or actuate. A composite sensor has been tested using compression elements stabilized with tensioning bands. The piezoelectric elements are arranged on the face diagonals with perimeter tension bands. Experimental piezoelectric response from this design was 1200 pC/N in air testing with peak hydrostatic response of 700 pC/N. The good device sensitivity as compared to properties of the base piezoelectric material is attributed to the internal arrangement of the piezoelectric elements and the tensioning system. Received: 28 April 1999 / Reviewed and accepted: 6 August 1999     

锂掺杂对P型Mg2Si0.6Sn0.4热电性能的影响

采用感应熔炼和真空热压法制备了掺Li的Mg2-xLixSi0.6Sn0.4（X=O，0．03，0．07，0．15，0．3）热电材料,电导率、Seebeck系数及热导率的测量表明，Li在Mg2-xLixSi0.6Sn0.4中起到受主作用，当x=0．07时Li掺杂Mg2-xLixSi0.6Sn0.4具有最好的性能，其功率因子和ZT值的最大值分别在480和600K时达到0.55×10^-3W／（m．K^-2）和0.16。     

Superlow thermal conductivity 3D carbon nanotube network for thermoelectric applications

Electrical and thermal transportation properties of a novel structured 3D CNT network have been systematically investigated. The 3D CNT net work maintains extremely low thermal conductivity of only 0.035 W/(m K) in standard atmosphere at room temperature, which is among the lowest compared with other reported CNT macrostructures. Its electrical transportation could be adjusted through a convenient gas-fuming doping process. By potassium (K) doping, the original p-type CNT network converted to n-type, whereas iodine (I(2)) doping enhanced its electrical conductivity. The self-sustainable homogeneous network structure of as-fabricated 3D CNT network made it a promising candidate as the template for polymer composition. By in situ nanoscaled composition of 3D CNT network with polyaniline (PANI), the thermoelectric performance of PANI was significantly improved, while the self-sustainable and flexible structure of the 3D CNT network has been retained. It is hoped that as-fabricated 3D CNT network will contribute to the development of low-cost organic thermoelectric area.     

Electrodeposition of n-type and p-type ZnSe thin films for applications in large area optoelectronic devices

ZnSe layers have been grown by a low temperature (65 °C) electrochemical deposition technique in an aqueous medium. The resulting thin films have been characterized using X-ray diffraction (XRD) and a photoelectrochemical (PEC) cell for determination of the bulk properties and electrical conductivity type. XRD patterns indicate the growth of ZnSe layers with (1 1 1) as the preferred orientation. PEC studies show p-type semiconducting properties for the as deposited layers and n-type ZnSe can be produced by appropriate doping. Annealing at 250 °C for 15 min improves the crystallinity of the layers and the photoresponse of the ZnSe/electrolyte junction. © 1998 Kluwer Academic Publishers     

Surface periodic domain structures for waveguide applications

We report the results of fabrication and investigations of surface periodic domain structures created by a set of quasi-point e-beam irradiations both on the Y- and X-cuts of LiNbO(3), and on Ti:LiNbO(3) and Zn:LiNbO(3) planar waveguides. Domain gratings with spatial periods from 4.75 to 7.25 μm were formed by a 25-keV e-beam. Doses from 500 to 2000 μC/cm(2) were used for different structures to estimate optimal fabrication conditions. The investigations allowed the visualization of the formed surface domain structures, estimation of their uniformity, and determination of waveguide generation of the second optical harmonic. The surface structures can be used in optical devices for the realization of quasi-phase-matched frequency conversion, which includes the creation of compact radiation sources based on waveguides.     

Effects of oxidation process on the tunneling barrier structures in room-temperature operating silicon single-electron transistors

We investigate the tunneling barrier structures in the room-temperature operating silicon single-electron transistors (SETs). The devices are fabricated in the form of the point-contact channel metal-oxide-semiconductor field-effect transistors with gate oxide formed by thermal oxidation or low-pressure chemical vapor deposition (LP-CVD). From the gate voltage and temperature dependence of the peak current in the SET characteristics, it is found that the thermal oxidation process leads to higher and narrower tunneling barriers. In some SETs with CVD-deposited gate oxide, thermally activated conduction over the low tunneling barriers is clearly observed in a wide temperature range from 100 K-300 K.     

Microstructure and thermoelectric performance evaluation of p-type (Bi,Sb)2Te3 materials synthesized using mechanical alloying and spark plasma sintering process

Journal of Materials Science: Materials in Electronics - In this paper, three p-type thermoelectric compounds, namely Bi0.5Sb1.5Te3, Bi0.3Sb1.7Te3, and Bi0.2Sb1.8Te3 were manufactured by mechanical...     

Recent progress in p-type doping and optical properties of SnO2 nanostructures for optoelectronic device applications

SnO(2) semiconductor is a host material for ultraviolet optoelectronic devices applications because of its wide band gap (3.6 eV), large exciton binding energy (130 meV) and exotic electrical properties and has attracted great interests. The renewed interest is fueled by the availability of exciton emission in nanostructures, high quality epitaxial films, p-type conductivity, and heterojunction light emitting devices. This review begins with a survey of the patents and reports on the recent developments on SnO2 films. We focus on the epitaxial growth, p-type doping and photoluminescence properties of SnO(2) films and nanostructures, including the achievements in our group. Finally, the applications of SnO(2) nanostructures to optoelectronic devices including heterojunction light emitting devices, photodetectors and photovoltaic cells will be discussed.