Seebeck Coefficient Of Samples Research Articles

Reduction in Processing Time in Ca3Co4O9+δ Ceramics through Nanoprecursors Produced by an Easily Scalable and Environmentally Friendly Process.

Attrition milling is an easily scalable and environmentally friendly process used to produce Ca3Co4O9+δ nanoprecursors in a relatively short time. Sintered materials produced through the classical solid-state method, involving ball milling, show much larger grain sizes and slightly lower density than those obtained in samples produced from attrition-milled precursors. On the other hand, electrical resistivity has been drastically decreased, accompanied with a slight decrease in the Seebeck coefficient in samples obtained from these attrition-milled precursors. Moreover, the use of an attrition milling process leads to a very important reduction in processing time (around 75%), together with a slight power factor improvement of around 10%, when compared to the classically prepared samples.

Investigation of thermoelectric properties of Cu2SnSe3 composites incorporated with SnSe

Cu2SnSe3 has been considered as a potential thermoelectric material owing to its cost-effective and nontoxic constituent elements along with its high electrical conductivity. However, its low Seebeck coefficient has been a concern towards realizing a high figure-of-merit. In the present study, Cu2SnSe3/xSnSe (x = 0, 5, 10, and 20 wt %) composite samples whose thermoelectric performance has been studied in the temperature range 10–375 K, shows that the Seebeck coefficient of sample containing 10% SnSe is ~3.6 times that of the pure. The incorporation of SnSe has resulted in a significant increase in electrical resistivity and Seebeck coefficient which is attributable to the decrease in carrier concentration with increase in SnSe content. Concurrently, a power factor (PF) of 35.60 μW/mK2 has been attained for x = 10% sample at 375 K. However, due to the increase in thermal conductivity with the addition of SnSe, the composites have lower ZT values than that of the pristine Cu2SnSe3 sample. Furthermore, the Vicker's microhardness, which is a key measure for the mechanical strength of a material, has distinctly improved by the addition of SnSe.

A tweezer as a thermoelectric tester

An easy operating tool has been developed for the quick measurement of thermoelectric power. The setup is made using a tweezer which consists of two circular copper plate electrodes. These copper electrodes are fixed to two arms of the tweezer which act as hot and cold probes. The setup has the very important advantage of easy sample mounting and dismounting in just a second and the Seebeck coefficient of the sample can be obtained in just 2–3 min. The present tool can provide a simple method for Seebeck coefficient measurement without any difficulty. One has to just place the sample and press the tweezer, data will be ready in minutes. The setup is clearly demonstrated for its proper working by measuring the Seebeck coefficients of some standard samples. The tool is designed by keeping focus mainly on new researchers or students in the field.

Anomalous effect of vanadium boride seeding on thermoelectric properties of YB22C2N

Vanadium boride seeded YB22C2N were synthesized and the thermoelectric properties investigated. YB22C2N is representative of the series of rare earth borocarbonitrides which is the potential long awaited n-type counterpart to p-type boron carbide. VB2 seeded samples of YB22C2N were prepared using VB2 directly as an initial additive and V2O3 which also results in formation of vanadium diboride in the final product. The resistivity and Seebeck coefficient of samples were measured in the temperature range of 323K to 1073K. A dramatic effect of thermal treatment on the Seebeck coefficient of VB2 seeded samples was observed, and it is indicated that there is possible partial intrinsic doping of vanadium into YB22C2N. VB2 is revealed to be a promising additive to improve the thermoelectric properties of YB22C2N. An enhancement of more than 220% of the maximum absolute value of the Seebeck coefficient was obtained while the resistivity was also reduced considerably.

Thermoelectric Properties of Indium-Added Skutterudites In x Co4Sb12

The high-temperature thermoelectric properties of InxCo4Sb12 (0.05 ≤ x ≤ 0.40) skutterudite compounds were investigated in this study. The phase states of the samples were identified by x-ray diffraction analysis and field-emission scanning electron microscopy at room temperature. InSb and CoSb2 were found as secondary phases in samples with x = 0.10 to 0.40. The filling limit of In into the CoSb3 cages of InxCo4Sb12 was in the range 0.05 < x < 0.10. The electrical resistivity, Seebeck coefficient, and thermal conductivity of the InxCo4Sb12 samples were measured from room temperature to 773 K. The Seebeck coefficient of all samples was negative. Reduction of the thermal conductivity by In addition resulted in a high thermoelectric figure of merit (ZT) of 0.67 for In0.35Co4Sb12 at 600 K.

Influence of sintering temperature on thermoelectric properties of La0.1Sr0.9TiO3 ceramics

Ceramic samples of La0.1Sr0.9TiO3 are synthesized by conventional solid state reaction technique at 1440℃, 1460℃, 1480℃ and 1500℃, respectively. Their thermoelectric properties are investigated. X-ray diffraction characterization confirms that the main crystal structure is of perovskite. Scanning electron microscope images indicate that all ceramic samples are dense and compact, and that the average grain size increases with the increase of sintering temperature. Electrical resistivity and Seebeck coefficient of samples are measured in the temperature range between room temperature and 800℃. In general, with the increase of sintering temperature, the electrical resistivity first increases, and then decreases. With the increase of sintering temperature, the absolute Seebeck coefficient first increases, and then decreases. A maximal power factor 21 μW·K-2·cm-1 is obtained at 165℃ for the sample sintered at 1480℃ because of its reletivly high absolute Seebeck coefficient and reletively low electrical resistivity.

Yttrium-doped effect on thermoelectric properties of La0.1Sr0.9TiO3 ceramics

Ceramic samples of La0.1YxSr0.9–xTiO3 with different yttrium concentration have been synthesized by conventional solid state reaction technique, and their thermoelectric properties have been investigated. X-ray diffraction characterization confirms that the main crystal structure is of perovskite, but with a small amount of second phase of Y2Ti2O7 for samples with x = 0.05, 0.08, and 0.10. SEM images indicate all ceramic samples are dense and compact, and the largest grain size appears in sample with x = 0.03 and 0.05. Also the second phase can also be identified from the SEM images for x = 0.05, 0.08, and 0.10 samples. Electrical conductivity and Seebeck coefficient of samples have been measured in the temperature range between 300 and 1100 K. With increasing of yttrium concentration, electrical resistivity decreases, and reaches 0.8 mΩ cm for x = 0.10 sample at room temperature. The absolute Seebeck coefficients increase monotonically with increasing temperature in the whole temperature range. Sample with x = 0.03 exhibits the highest absolute Seebeck coefficient 219 μV K−1 at 1059 K, as well as the maximum power factor 11 μW cm−1 K−2 at 624 K.

Effect of Al Substitution on the Thermoelectric Properties of the Type VIII Clathrate Ba8Ga16Sn30

Single-crystal samples of the type VIII clathrate Ba8Ga16−xAlxSn30 (0 ≤ x ≤ 12) were prepared by the Sn-flux method, and the structural and electrical properties were studied from 300 K to 600 K. The lattice parameter increases linearly as x is increased from 0 to 10.5, which is the solubility limit of Al. For all samples, the electrical conductivity σ decreases monotonically as the temperature is increased. σ(T = 300 K) increases from 1.88 × 104 S/m for x = 0 to 3.03 × 104 S/m for x = 2, and then gradually decreases to 2.4 × 104 S/m with further increase of x to 8. The increase of σ for Al-substituted samples is attributed to enhancement of carrier mobility. The Seebeck coefficients of samples with 0 ≤ x ≤ 8 are negative with large values, and the absolute values increase from 240 μV/K to 320 μV/K as the temperature increases from 300 K to 600 K. At 300 K, the effective mass m*/m0 is in the range from 0.53 to 0.67, and the samples with x = 6 and x = 8 have a rather low thermal conductivity of 0.72 W/mK and 0.78 W/mK, respectively. ZT reaches 1.2 at 500 K for x = 6.

Microstructures for characterization of seebeck coefficient of doped polysilicon films

CMOS based thermoelectric micro-transducers have been demonstrated for various applications. To achieve better design and optimization of such micro-transducers, the Seebeck coefficient of doped polysilicon thin film needs to be measured accurately with respect to optimization effort in process and structure design of micro-transducers. A novel circular test structure is firstly presented to get accurate value of Seebeck coefficient in this paper, while the known planar and cantilever test structures are fabricated together and characterized separately to validate the measured Seebeck coefficient of samples with the same process conditions for comparison. Seebeck coefficient measured by the circular structure shows good agreement with the result measured by cantilever structure, while there is an error of about 14% for the result given by planar structure. The circular test structure is a good at accurate testing of the average absolute values of Seebeck coefficient of p-type and n-type. Strength and drawback for the three structures are summarized.

급속 응고 된 Bi2Te3-PbTe계 열전소재의 미세구조와 열전 특성

In order to design nano structured materials with enhanced thermoelectric properties, the alloys in the pseudo-binary <TEX>$Bi_2Te_3$</TEX>-PbTe system are investigated for their micro structure properties. For this synthesis, the liquid alloys are cooled by the water quenching method. Micro structure images are obtained by using an electron probe micro analyzer(EPMA). Dendritic and lamellar structures are clearly observed with the variation in the composition ratio between <TEX>$Bi_2Te_3$</TEX> and PbTe. The increase in the <TEX>$Bi_2Te_3$</TEX> composition ratio causes to change of the structure from dendritic to lamellar. The Seebeck coefficient of sample 5, in which the mixture rate of <TEX>$Bi_2Te_3$</TEX> is 83%, is measured as the highest value. In contrast, the others decrease with the increase of the <TEX>$Bi_2Te_3$</TEX> composition ratio. Meanwhile, p-type characteristics are observed in sample 6, at 91%-<TEX>$Bi_2Te_3$</TEX> mixture rate. The power factors of the all samples are calculated with the Seebeck coefficient and resistivity.

Transport properties of SnTe–Bi 2Te 3 alloys

Bismuth telluride based alloys have been a class of important thermoelectric materials widely used in cooling devices around room temperature. In this work, a series of polycrystalline samples of ternary compounds in the SnTe–Bi 2Te 3 system were prepared by rapid quenching of the melt followed by a sintering procedure of compacted pellets. The electrical conductivity and Seebeck coefficient of samples with various compositions were measured from room temperature up to about 600 K. The measured results show that the transport properties strongly vary with the composition and temperature. The microstructure in this system shows randomly oriented fine plate-shaped grains with multi-layered structure.

Structure, Stoichiometry, and Properties of the Chimney-Ladder Phases Ru2Ge3+x (0

The preparation and physical characterization of non-stoichiometric Ru2Ge3+x (0≤x≤1) are reported for the first time. The defect TiSi2-type chimney-ladder structure is maintained for the full stoichiometry range. The resistivity of Ru2Ge3+x increases systematically with x from 300 mΩ cm, x=0 –3 Ω cm, x=1 at 300 K. The temperature dependence is consistent with a variable range-hopping mechanism for x≥0.6. The Seebeck coefficients of samples do not evolve simply with x. A low thermal conductivity (κ300 K=0.03 W/K cm) suggests that Ru2Ge3 has some of the properties of a phonon-glass–electron-crystal. The low value of the thermoelectric figure of merit ZT=3.2×10−3 (T=300 K) calculated for Ru2Ge3 is due primarily to a low conductivity.

Developments in manufacture and application of polycrystalline diamond and boron nitride

TiB2/B4C composite ceramics are prepared via hot pressing, in which the TiB2 particles are formed by introducing TiC0.78 and through the reaction between B4C and TiC0.78. The electrical and thermal conductivities and Seebeck coefficient of samples containing 0, 12.5 and 25.4 vol% TiB2 are measured from room temperature up to 1200 K. The results show that the transport properties of the samples vary with the TiB2 content. The transport properties of a 12.5 vol% TiB2/B4C sample are dominated by the B4C matrix as in undoped B4C ceramics, whilst the transport properties of a 25.4 vol% TiB2/B4C sample are dominated by TiB2 particles. The figure of merit of the 25.4 vol% TiB2/B4C sample is higher than that of the undoped B4C ceramic sample between room temperature and about 700 K, which indicates that it is possible to improve the thermoelectric properties by selecting an optimum combination of different materials.

Effect of titanium carbide addition on the thermoelectric properties of B 4C ceramics

TiB 2/B 4C composite ceramics are prepared via hot pressing, in which the TiB 2 particles are formed by introducing TiC 0.78 and through the reaction between B 4C and TiC 0.78. The electrical and thermal conductivities and Seebeck coefficient of samples containing 0, 12.5 and 25.4 vol% TiB 2 are measured from room temperature up to 1200 K. The results show that the transport properties of the samples vary with the TiB 2 content. The transport properties of a 12.5 vol% TiB 2/B 4C sample are dominated by the B 4C matrix as in undoped B 4C ceramics, whilst the transport properties of a 25.4 vol% TiB 2/B 4C sample are dominated by TiB 2 particles. The figure of merit of the 25.4 vol% TiB 2/B 4C sample is higher than that of the undoped B 4C ceramic sample between room temperature and about 700 K, which indicates that it is possible to improve the thermoelectric properties by selecting an optimum combination of different materials.

Some properties of flash-evaporated Ga1−xAsx films

a-Ga1−xAsx films containing small GaAs crystallites were prepared by flash evaporation onto low-temperature glass substrates. The As content in the films was varied from 41 to 69 at.%. Thermoelectric power measurements indicate that Ga-rich films are n-type and As-rich films are p-type, but the Seebeck coefficients for samples near the stoichiometric ratio were too small to measure. The optical gaps vary with As content in a way that is consistent with the suggestion that the material appears to be an alloy of a-GaAs and the excess component. High-temperature activation energies place the Fermi level near midgap in all samples and this is in line with the suggestion that this class of materials tend to self compensate as the film grows.