Papers by Keyword: Seebeck Coefficient

Abstract: The efficiency of a thermoelectric device depends on material properties through the figure of merit, Z = σS²/κ, where σ, S, and κ are electrical conductivity, Seebeck coefficient, and thermal conductivity, respectively. To maximize the thermoelectric figure of merit of a material, high electrical conductivity, high Seebeck coefficient, and low thermal conductivity are required. This work has focused on the synthesis of a mesoporous titania films for its application in thermoelectric generation. The mesoporous titania film was synthesized with titanium tetraisopropoxide. The triblock copolymer, Pluronic P-123 (EO₂₀ PO ₇₀EO ₂₀) was used as surfactant in 1-propanol. As a result, an improvement of electrical conductivity and reduced annealing with a lowering of thermal conductivity by distributions of pores were found to be effective to enhance the thermoelectric property.

Abstract: This study has devised a tool insert with micro built-in thermocouples in order to establish a cutting-temperature measuring method for practical use. This tool insert possesses seven pairs of micro Cu/Ni film thermocouple near the cutting edge on the rake face. In this study, Cu film and Ni film were deposited in the micro grooves corresponding to a circuit pattern of the micro thermocouple by means of electroless plating and electroplating. This paper shows the results of the investigation concerning the electrical properties of the micro Cu/Ni film thermocouples. The influence of the current density in electroplating on the electrical resistivity of the films was examined. The characteristic of the Seebeck property of the micro Cu/Ni film thermocouple was investigated in a temperature difference of up to 600 K with a heating apparatus developed. The Seebeck coefficient of the micro Cu/Ni film thermocouple was smaller by 28 % than that of a Cu/Ni wire thermocouple. The result implies that the degradation in the Seebeck property of the micro Cu/Ni film thermocouple derives from an existence of an impurity between Cu film and Ni film in the hot junction.

Abstract: Thermoelectricity has gained special interest due to its potential applications, especially the advancements in the electronic devices with very low power consumption. Thermoelectric materials can be used to make energy conversion devices that generate power from thermal sources. Multiferroic oxides, in particular cobaltates, have been actively studied as a new type of thermoelectric material (1). The crystal structure of these cobaltates offers a possibility to manipulate Seebeck coefficient, electric conductivity, and thermal conductivity to optimize the figure of merit ZT. The theoretical explanation and experimental observations by some investigators proved the candidature of multiferroic materials for thermoelectric generation. Many semiconducting multiferroic oxides are showing spin dependent Seebeck coefficient (2-3). Moreover, most of these oxides are inherently stable at high temperatures in air, making them a suitable material for high temperature applications. In this work we have investigated the multiferroic and thermoelectric properties of thinfilms of doped cobalt oxide matrices. The observations confirmed that these materials are suitable for thermoelectric generation.

Abstract: The Seebeck coefficient of heavily-nitrogen-doped n-type polycrystalline 3C-SiC (n-SiC) and platinum (Pt) thin films has been measured from room temperature up to 300 °C by using a microfabricated test structure. At room temperature, the absolute Seebeck coefficient of the n-SiC is -10 μV/°C. With ambient temperature increase, the absolute Seebeck coefficient of the n-SiC is found to gradually increase, reaching -20 μV/°C at 300 °C.

Abstract: Samples of Cr doped cobalt ferrite were prepared by co-precipitation route. These particles were characterized by X-ray diffraction (XRD) at room temperature. The structural properties were observed before and after sintering. The FCC spinel structure was confirmed by XRD patterns of the samples. The crystallite sizes lie in the range of 37-60 nm. DC electrical properties as a function composition were measured. Scanning electron microscopy was used in order to investigate the surface morphology of the prepared samples. The system for thermoelectric power measurement was designed, developed and calibrated in the laboratory. The room temperature thermoelectric power was measured for the prepared samples. The magnitude of Seebeck coefficient depends on the composition and resistivity of the samples. The obtained values of Seebeck coefficient for CoFe₂O₄ are in good agreement to the reported values. Determined values of Seebeck coefficient for other studied compositions are an addition to the literature.

Abstract: Thermoelectric is an ever evolving field that serves many critical needs (cooling and power generation) in the industry. The key objective of this work is to fabricate Bismuth Telluride (Bi₂Te₃) thin-films by varying the various process parameters using a radio-frequency (RF) magnetron sputtering disposition technique. Characterization methods such as four point probe resistivity, surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), Seebeck coefficient and thermal diffusivity are performed on the N and P-type Bi₂Te₃ films. The samples are analysed for their electrical properties in relation to the evolved microstructures, for how the process parameters of sputtering and annealing affect these changes. The results demonstrate that N-Type film (S2) processed using sputtering parameters of 7mT, 100W, 50sccm of argon flow under room temperature for 30mins with no annealing and the P-Type film processed using sputtering parameters of 7mT, 100W, 60sccm under room temperature for 30mins with institute annealing at 200°C for 2h exhibit desirable thermoelectric properties suitable for cooling application in microelectronic and optoelectronic devices, optimizing their performance and reliability.

Abstract: PbS thin films with corrugated structure were synthesized on glass substrates by dip coating. The surface of the films was found to be corrugated. XRD analysis confirmed the formation of crystalline PbS nanoparticles with average grain size 14nm. From thermo power measurements, the conductivity of the samples was found to be of n type. Band gap of the films was estimated as 1.7eV from absorption spectra.

Abstract: This paper discloses the design and finite element modeling of a flexible micro thermoelectric generator (TEG), which incorporates microfluidic channel to enhance the role of the heat sink. Polyimide substrate is used to accounts for the flexibility while PDMS microfluidic is chosen in the analysis. A study has been conducted to optimize the design parameters of thermo element length, cross-sectional area and the number of thermocouples acceptable in a prescribed area. The polysilicon thermocouple with 0.7 µm thick and 5 µm width is found to have the optimum length of 36 µm. For a device in the size of 1mm x 1mm and with a 5 K temperature difference across the heat source and heat sink, the open-circuit voltage is 1.373 V and the output power is 0.831 µW/mm² under matched load resistance. The computational result also shows that by increasing the footprint area of the thermocouples with the step of 1 mm², a substantial increase in the output voltage and power is observed.observed.

Abstract: Cobblestone-like CoSb3 nanoparticle films have been achieved via a catalyst-free vapor transport growth technique. The thermoelectric properties of the nanoparticle films were measured from room temperature to around 500 oC. The resultant CoSb3 nanoparticle films show high electrical conductivities due to clean particle surfaces. A maximum power factor reaches 1.848×10−4 W/mK2 at 440 oC. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.

Abstract: NiCr-NiSi K-type thin film thermocouples with multi-layer structure were fabricated on Ni-based superalloy substrates (95 mm×35 mm×2 mm). The multi-layer structure contains NiCrAlY buffer layer (2 μm)/ thermally grown Al₂O₃ bond coating (200 nm)/ Al₂O₃ insulating layer (8 μm)/ NiCr-NiSi thin film thermocouples (1 μm)/ Al₂O₃ protecting layer (500 nm). The samples were statically calibrated in a tube furnace in the temperature range from 170 °C to 610 °C. The results show that the resistance of Al₂O₃ insulating layer is about 14.6 kΩ at 800 °C and exceeds 100 MΩ at room temperature. The Seebeck coefficient a of the samples is about 34 μV/°C, and the sensitivity coefficient K is greater than 0.8 in the temperature range from 170 °C to 610 °C. The maximal sensitivity coefficient is about 0.97 at 265 °C.