N-type thermoelectrics

Dun, C., Hewitt, C A., Huang, H., Xu, J., Montgomery, D.S., Nie, W, Jiang, Q., Carroll, D.L., 2015. Layered Bi2Se3 nanoplate/polyvinylidene fluoride composite based n-type thermoelectric fabrics. ACS Appl. Mater. Interfaces 7,7054-7059. 

Chabinyc, M.L., Hawker, C.I., Segalman, R.A., 2014. Power factor enhancement in solution-processed organic n-type thermoelectrics through molecular design. Adv. Mater. 26,3473-3477. 

R., Koumoto, K., 2015. Flexible n-type thermoelectric materials by organic intercalation of layered transition metal dichalcogenide TiSj. Nat. Mater. 14, 622-627. 

Perovskite-type calcium manganates (CaMnOs- ) are stable in air at temperatures exceeding 1200 K [13,14]. They are synthesized from inexpensive and nontoxic materials, and exhibit relatively high ZT values, exceeding 0.15 at 1000 K [14,15], when appropriately substituted. Such materials are applicable as n-type thermoelectrics in all-oxide thermoelectric converters where power densities up to 240mW/cm are reached with converters operated in air [16]. 

The development of novel p- and n-type thermoelectric oxides and their tests in high-temperature converters demonstrate the large potential of this class of thermoelectric materials and motivates the further exploration of hitherto unknown compositions and structures. 

Bocher, L Aguirre, M.H., Logvinovich, D Shkabko, A., Robert, R Trottmann, M and Weidenkaff, A. (2008) CaMnl- Nb 03 (x < 0.08) perovskite-type phases as promising new high-temperature n-type thermoelectric materials. Inorg. Chem., 47 (18), 8077. 

Weidenkaff, "CaMni- xNbiOy (x< 0.08) Perovskite-Type Phases As Promising New High-Temperature n-Type Thermoelectric Materials," Inorg. Chem., 47[18] 8077-85 (2008). 

A second historical line which, is of paramount importance to the present understanding of solid state processes is concerned with electronic particles (defects) rather than with atomic particles (defects). Let us therefore sketch briefly the, history of semiconductors [see H. J, Welker (1979)]. Although, the term semiconductor was coined in 1911 [J. KOnigsberger, J, Weiss (1911)], the thermoelectric effect had already been discovered almost one century earlier [T. J. Seebeck (1822)], It was found that PbS and ZnSb exhibited temperature-dependent thermopowers, and from todays state of knowledge use had been made of n-type and p-type semiconductors. Faraday and Hittorf found negative temperature coefficients for the electrical conductivities of AgzS and Se. In 1873, the decrease in the resistance of Se when irradiated by visible light was reported [W. Smith (1873) L. Sale (1873)]. It was also... 

Although the presently obtained absolute values of power factors still need to be improved, these compounds may offer a n-type boride counterpart to the well known p-type boron carbide which is one of the few thermoelectric material viable for extremely high temperature use (1500 K), and further research on the R-B-C(N) compounds is merited. 

Interesting problems remain to be solved. Although the figure of merit is still quite low due to the poor density, can the homologous R-B-C(N) borides be den-sified and/or doped to become a viable n-type counterpart to boron carbide which is an exemplar p-type high temperature thermoelectric compound ... 

This expression shows that the imposition of a temperature difference dT in the absence of any current produces a difference d i in electrochemical potential i.e., d ife) = —z/a, dT. This effect is known as the thermoelectric effect, and the ratio d i/e)/dT, or A(f,/e)/Ar = —ZiCii is known as the Seebeck coefficient (1823), or thermoelectric power.Experimentally, the difference of electrochemical potential may be measured by a voltmeter under open circuit conditions, and dT, measured by means of thermocouples a, is thereby experimentally determined. As defined here for p-type (n-type) material the measured Seebeck coefficient is a positive (negative) quantity. For, and both increase in the direction of increasing hole or electron concentration, which is in a direction opposite to the increase in temperature. Comparison with (6.9.2) shows that Ui = ZiSgfe. Then Eq. (6.9.6) becomes... 

Thermoelectric materials have been used extensively for thermal sensing, energy conversion (heat to electricity), and for cooling (Peltier effect). In general, thermoelectric devices consist of n-type and p-type semiconductor constituents connected electrically in series and thermally in parallel [151]. While energy conversion efficiencies for thermoelectric devices are not yet competitive with conventional refrigerator or power generation systems, it is possible to achieve enhanced efficiencies... 

Fig. 13.22 (a) Proposed thermoelectric nanowire-based device within an alumina nanotemplate, (b) enlarged view of a few n-type and p-type nano-bundle elements connected electrically in series and arranged thermally in parallel (nanotemplate removed). Reprinted with permission from ref. [153]... 

Bismuth telluride with the stoichiometric composition ratio (Bi TCj) is electronically neutral. However, the common carrier of the bismuth telluride alloy can be modified by adjusting the percentage of tellurium or bismuth incorporated. If the alloy is tellu-ride-rich, it can be n-type. In order to be p-type, the composition of the bismuth telluride alloy should be bismuth-rich instead of telluride-rich [59]. This is advantageous since the material deposition development can focus on a single material system which will yield both the n- and p-branches of the thermoelectric probes. 

Hence, it probably causes the deterioration of thennodectiic performance of FGM element at hi temperature range. However, such a situation is usual for a thermoelectiic device which has the jimction between thermoelectric element and electrode or the junction between n lype thermoelectric element and p type one. The durability for Si-Ge device and Pb-Te one has been already established at hi temperature range 7. Such an experience can be apphed to the constitution of FGM thermoelectric element. 

In this paper, thermoelectric figure of merit for n-type sintered materials of SiGe and PbTe has theoretically been estimated considering effects of grain boundaries on carrier mobility and Seebeck coefficient based on a model. 

Fig.l. Optimal functions of thermoelectric material inhomogeneity n-type Bi2Te2jSeo.i + (0,09... O.OSjCdCh p-type Bio.sSbi.sTe + 4% Te... 

The purpose of this work is to discuss the anisotropic thermoelectricity of n-type Bi2Te2.85Seo.15 single crystal on the basis of anisotropic carrier scattering. 

Fabrication of N-type Polycrystallinc Bi-Sb and Tlicir Thermoelectric Properties... 

The present work reports on mechanical alloying process of the n-type Bi-Sb [4-10] solid solution which is known to be the best material in low temperature region. The effect of milling conditions on the microstructure development and the thermoelectrical properties were studied. 

Figure 2 shows the compositional dependence of carrier density. As shown in the figure, carrier density strongly depended on composition of the samples. The samples of composition y > 0.7 showed p-type conduction while those of y < 0.7 showed n-type conduction. This result is quite different from the results of typical bismuth telluride based materials which is made by melt process[8]. All n-type samples had low Hall mobilities around 100 cm /Vs therefore only p-type compositions are selected to further study on thermoelectric properties. 

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