China
Africa
Explore chapters and articles related to this topic
Long-Term Non-Operating Reliability of Selected Electronic Products
Published in Judy Pecht, Michael Pecht, Long-Term Non-Operating Reliability of Electronic Products, 2019
There are two kinds of coolers used in infrared detector packages: thermoelectric coolers and cryogenic coolers. Thermoelectric coolers are commonly made by Bismuth Telluride. The principle of the thermoelectric cooler, the Peltier effect, is used for cooling by simply reversing the current's direction. Temperatures differentials of 60 to 65°C can be achieved for a single couple, or stage, using an infrared detector as a heat load. If several couples or stages are cascaded, lower temperatures can be reached. Joule-Thomson coolers use a Joule-Thomson cryostat, a miniature gas liquefier that can be placed directly in the coolant chamber of a detector package. In its most common form, a cryostat consists of a cylindrical mandrel carrying a helically wound coil of finned metal tubing. The finned tubing serves as the countercurrent heat exchanger. The cryostat slides smugly into the inner steam of the dewar, and the steam of liquefied gas is directed toward the back of the surface carrying the sensitive element. After expansion, the cooled gas flows along the heat exchanger and extracts heat from the incoming gas. Although most cryostats are designed for use with nitrogen or argon, they can also be used with the various members of the Freon family to produce a wide range of temperatures.
Fabrication Routes for Nanostructured TE Material Architectures
Published in D. M. Rowe, Materials, Preparation, and Characterization in Thermoelectrics, 2017
Muhammet S. Toprak, Shanghua Li, Mamoun Muhammed
Various schemes are reported for the precipitation of the components and conversion of these coprecipitated powders to Bi2Te3 powder through hydrogen reduction. Ritter et al. has reported a room-temperature coprecipitation process of bismuth telluride precursor (Bi2O3, 3TeO ⋅ xH2O) in aqueous media, which is then converted to polycrystalline Bi2Te3 via hydrogen reduction at 275°C for 12 h.22 Toprak et al. adapted a similar approach, replacing bismuth oxide with bismuth oxalate that has higher reactivity and thus could reduce the time required for hydrogen reduction significantly down to 2 h at 350°C producing 40 nm nanocrystals of Bi2Te3.23 This is a powerful method and is proven to be successful in the synthesis of bulk quantities of TE powder with the desired composition. The use of metal-organo complexes as a route to mixed cation oxide powders has also been utilized for the synthesis of various TE materials. For instance, in the synthesis of Bi2Te3, Ritter et al. reported an organic precursor prepared by a reaction mixture of Bi2O3, ethylene glycol, metallic Te, and dl-tartaric acid and nitric acid. This precursor was then calcined and reduced under hydrogen to form nanocrystalline Bi2Te3 powder.24
ThermoMechanical Design
Published in Fred D. Barlow, Aicha Elshabini, Ceramic Interconnect Technology Handbook, 2018
Thermoelectric coolers (TEC) are solid-state heat pumps based upon the Peltier effect without any fluids or moving mechanical parts. In the Peltier effect, a potential is applied to two junctions as shown in Figure 3.15. Heat will be expelled from one junction and absorbed into the other in an amount proportional to the applied current. The thermoelectric cooler consists of an array of junctions using bismuth telluride (Bi2Te3), lead telluride (PbTe), or silicon germanium (SiGe). These materials are doped during fabrication to optimize the parameters of the cooler. Bismuth telluride has been found to have the best performance and is widely used for thermoelectric coolers.
Thermoelectric materials developments: past, present, and future
Published in Science and Technology of Advanced Materials, 2021
Prof. Koumoto has made striking advancements in the development of environmental-friendly and earth-abundant thermoelectric materials. The classical high-performance thermoelectric materials such as bismuth telluride, lead telluride, etc. tend to contain very rare or toxic elements. Prof. Koumoto led the early development in achieving high thermoelectric performance in oxides and sulfides, through novel principles such as nanoblock integration, artificial superlattice structures, etc. His notable work on hybridization via organic molecules intercalation in layered sulfides achieved flexible high-performance thermoelectrics, which were targeted for wearable IoT power generation. For this Focus Issue, Prof. Koumoto and coworkers contributed an original paper on the recent development of a novel abundant sulfide thermoelectric material [9].
Multi objective optimization of an irreversible thermoelectric heat pump using evolutionary algorithms and response surface method
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Saman Meshginnezhad, Ehsanolah Assareh, Arash Erfani, Mojtaba Alirahmi, Tohid Jafarinejad
In Figure 1, we see the schematic of a single-stage thermoelectric heat pump, a thermoelectric heat pump includes two-layer ceramics contacting metals and thermocouple pairs, which are divided into two class of n and p type material. Material for creating thermoelectric is bismuth telluride (Bi2Te3). This material has been selected due to its potential for improving of ZT value by structural and composition modification and the best thermoelectric material available near room temperature that achieves a higher temperature differential (Di, Sun, and Qin 2011). The temperature depends on the Bi2Te3 features of the thermoelectric material. Characteristics of the material utilized in this study are as follows (Xuan et al. 2002):
Thermodynamic investigations with maximum power point tracking (MPPT) of hybrid thermoelectric generator-heat pump model
Published in International Journal of Ambient Energy, 2020
The thermoelectric converter comprises P/N-type semiconductor couple modules rationalised in electrical-series and thermal-parallel practice is demonstrated in Figure 2(a). The converter develops an electrical voltage in indicative magnitude because of the difference in temperature at hot-cold terminals. The theoretical model of the thermoelectric converter revealing the output voltage generation due to the flow of heat is given in Figure 2(b). Bismuth Telluride, a semi-metal, is used as the thermoelectric material for TEG. In the present configuration, there are 31 thermoelectric couples in the module and 6 such modules are coupled in series in order to enhance the output voltage/power. In the figure provided, Th–TH reports for the hot terminal and heat source, whereas Tc–TL reports for the cold terminal and heat sink temperatures, respectively. It has been observed that for the development of substantial voltage output large temperature differential is the key factor in the system.