Seebeck coefficient power

The Seebeck coefficient is frequently called the thermoelectric power or thermopower, and labeled Q or S. Neither of these alternatives is a good choice. The units of the Seebeck coefficient are not those of power. The symbol Q is most often used to signify heat transfer in materials. The designation S can easily be confused with the entropy of the mobile charge carriers, which is important because the Seebeck coefficient is equivalent to the entropy per mobile charge carrier (see Supplementary Material S3). 

Dc, ac, impedance, and thermoelectric power of the compounds 33-38 in Fig. 9 have been investigated in detail. The measured temperature dependence of the thermoelectric power of 33-38 in thin film varied approximately exponentially with temperature. Compared to 38, the absolute value of the thermopower for the film of 34 is larger by nearly a factor of 3. The positive sign of Seebeck coefficient confirms that thin films of the compounds behave as a p-type semiconductor [46],... 

We must make a compromise to obtain the following properties the high TE power (Seebeck coefficient) a, the low electrical resistivity p, and the low thermal conductivity k. These properties are an antinomy and a specialized semiconductor can play a role to satisfy these properties. The figure of merit, Z is shown in following equation ... 

The Seebeck coefficients (thermoelectric powers) of Na WOs have been measured over a wide range of x values at room temperature (300° K.). At this temperature, the residual resistance, p0, and thermal resistance, pt, are comparable, the value of p0 being between pt and 2pt. Nevertheless, one would expect to a first approximation (10) that S = (1/3) (ir2k2T/e ), where S is the Seebeck coefficient, k is Boltzmann s constant, e is the electronic charge, and f is the Fermi energy. For free electrons, the Fermi energy f = (h2/2m ) (3n/87r)2/3 where h is Planck s constant, m is the effective mass, and n is the density of free electrons. Since n is proportional to x, f varies as x2/3 and S varies as xr2/3. 

Couples comprised of two different pure metals have low Seebeck coefficients since the absolute thermopowers of pure metals are in the microvolt per degree Celsius range (superconductors have zero absolute thermopowers). The difference between the absolute thermopowers of each metal in a couple yields the observed TE power of the couple. However, in metals (with half-filled bands) the electrons and holes have a cancelling effect the TE voltage produced is small. This makes them unsuitable for use in most TE apphcations with the exception of thermocouples that are used for temperature measurements. Semiconductors, by contrast, can be doped with an excess of electrons... 

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... 

The temperature dependence of Seebeck coefficient and electrical resistivity of the sintered Mn-Si element were measured simultaneously by the power factor measurement device 5. The temperature difference was kept at constant lOK in the temperature range up to HOOK. HaU coefficient and electrical resistivity were measured with van der Pauw method up to 500K. The each sample is spot-welded a 50 yU m platinum wire as the electrode. The current and magnetic field were 0.1 A and 0.356T respectively in the HaU measurement. In the measurement of electrical resistivity the current was 3mA... 

By the usage of two staged graded FGM element the FGM effect on thermoelectric performance such as Seebeck coefficient and power factor was investigated. Moreover, the thermoelectromotive force for overaU temperature difference was also evaluated. 

Thermoelectric power measurements indicated that all the compounds are p-type semiconductors and thermo - emf increases with an increase in Zn2+ content (Table 1). In this system Zn + ions with stable oxidation state occupy A sites. With the introduction of Zn + in the lattice the concentration of Cu occupying octahedral site decreases, however the concentration of Mn ions at the octahedral sites of the series Cuj. Zn MnCr04 remains same. Therefore, with the increase in value of Zn2+, the number of ion pairs of Mn3+ - Mn + start decreasing thereby increasing the resistivity of Zn rich compositions. Seebeck coefficient ( a ) varied between +26 to +66 pV/K which shows with increase in zinc contents of the spinel, the Seebeck coefficient increases. 

TABLE 16.12 Nominal Seebeck Coefficients (Thermoelectric Power), aAB ( iV7°C) [36]... 

Hakim investigated the electrical properties of In203 and ITO films prepared by spray pyrolysis by measuring the electrical resistivity as a function of temperature [100], the Hall effect and the thermoelectric power [99]. He observed a very complicated dependency of the electrical resistivity on the temperature with an activation energy of about 0.07-0.1 eV for the temperature range of 70-190°C. These low values indicate shallow donor levels [124]. The Seebeck coefficients or the thermoelectric power of ITO films were in the range of 16 to 200 pV K . 

In the Seebeck or thermoelectric effect a voltage difference arises between two contacts to a semiconductor when they are held at different temperatures. Results are usually expressed in terms of the Seebeck coefficient, the ratio of the voltage difference to the temperature difference. The polarity of the thermoelectric power determines the sign of the majority carrier as the polarity of the cold junction. CompUcations (and incorrect interpretations) may arise if the space charge layers are too thick or the carrier concentration too low. The technique does not distinguish between electronic and ionic conduction. 

DTEGs are an alternative to resistive gas sensors. Accurate, rapid and long-term stable gas sensors have been presented in this chapter. The main advantage of DTEGs is the measurand thermopower or Seebeck coefficient . In contrast to conductometric gas sensors, the measurand thermo-power is not influenced by changes in the geometry of the gas sensitive... 

Thermoelectric Power. Several groups have investigated the thermoelectric power of K2Pt(CN)4Xo.8(H20) [X = Cl (142,296), Br(142,254, 309)]. In all cases a low value for the room temperature Seebeck coefficient, indicative of metallic behavior, was reported. While positive values characteristic of hole carriers are reported for the chloro complex (142, 296) both positive (309) and negative (142,254) (eharge carrier) values of the Seebeck coefficient have been reported for the bromo complex. A negative thermoelectric power... 

The role of ions in the thermoelectric responses of different PEDOT derivatives was investigated (Wang et al., 2015a). Unexpected significant increases in the thermo-induced voltage was observed at high humidity levels, which is identified as an ionic Seebeck effect. The total thermo-power appears as the sum of the ionic Seebeck coefficient and the... 

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