Thermoelectric-Generator-Based DC–DC Conversion Networks for Automotive Applications

Maximizing electrical energy generation through waste heat recovery is one of the modern research questions within automotive applications of thermoelectric (TE) technologies. This paper proposes a novel concept of distributed multisection multilevel DC–DC conversion networks based on thermoelectric generators (TEGs) for automotive applications. The concept incorporates a bottom-up design approach to collect, convert, and manage vehicle waste heat efficiently. Several state-of-the-art thermoelectric materials are analyzed for the purpose of power generation at each waste heat harvesting location on a vehicle. Optimal materials and TE couple configurations are suggested. Moreover, a comparison of prevailing DC–DC conversion techniques was made with respect to applications at each conversion level within the network. Furthermore, higher-level design considerations are discussed according to system specifications. Finally, a case study is performed to compare the performance of the proposed network and a traditional single-stage system. The results show that the proposed network enhances the system conversion efficiency by up to 400%.     

Oxide Thermoelectric Materials: A Structure–Property Relationship

Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity (ZT ≈ 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure–property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron–phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.     

Towards the Use of Cu–S Based Synthetic Minerals for Thermoelectric Applications

Semiconductors - Most of the energy produced is lost, mainly as waste heat. Thermoelectricity, which can directly convert heat into electricity, is seen with huge potential to recover part of such...     

Thermoelectric Properties of Heavy Rare Earth Filled Skutterudites Dy y Fe x Co4?x Sb12

Heavy rare earth element Dy-filled skutterudites (Dy _y Fe _x Co_4?x Sb₁₂) have been synthesized by a melting–quenching–annealing method and sintered by the spark plasma sintering technique. Our results suggest that single-phased Dy _y Fe _x Co_4?x Sb₁₂ compounds could be obtained when the Fe content is less than 1.5. The maximum filling fraction of Dy in skutterudites increases with increasing Fe content. We also found significant lattice expansion induced by Fe substitution at Co sites and Dy filling in the voids. The electrical conductivity, Seebeck coefficient, and thermal conductivity have been measured in the temperature range from 300?K to 800?K. The low-temperature Hall coefficient and carrier mobility are reported in the temperature range from 2.5?K to 300?K. The power factor for Dy _y Fe _x Co_4?x Sb₁₂ increases with increasing Fe content. A significant reduction in lattice thermal conductivity is observed in heavy rare earth element Dy-filled skutterudites due to the low localized vibrational frequency of Dy that effectively scatters low-frequency lattice phonons. The sample with composition Dy_0.41Fe_1.45Co_2.55Sb_12.28 has lattice thermal conductivity as low as 1.05?W?m^?1?K^?1 at room temperature. The thermoelectric figure of merit (ZT) reaches a maximum value of 0.67 at 750?K.     

In?Situ Growth of a Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

The compound Yb₁₄MnSb₁₁ is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000°C in the vacuum of space. Although Yb₁₄MnSb₁₁ shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000°C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14?years. The purpose of the present work is to measure the sublimation rate of Yb₁₄MnSb₁₁ and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb₁₄MnSb₁₁ at 1000°C (??3?×?10^?3?g/cm²?h) and efforts to reduce the sublimation rate with an in?situ grown Yb₂O₃ layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb₁₄MnSb₁₁, the scales did not prove to be sublimation barriers.     

Nanostructured Thermoelectric Materials for Temperatures of 200–1200 K Obtained by Spark Plasma Sintering

Semiconductors - The broad application of thermoelectricity is constrained by the low efficiency of thermoelectric elements, which is mainly determined by the thermoelectric figure of merit of...     

Electronics Packaging Technologies for Automotive Electronics

To enable automotives to be more intelligent and reliable, increasing amounts of electronic systems are embedded inside automotives. Moreover, adopting advanced packaging technologies, such as System-in-Package （SIP）, not only can reduce the overall module size but also the number of components, i.e. less handling and bill-of-materials.     

High Tc Superconducting Materials for Strong Current Applications： Approach at the First Stage

Strong current and large-scale application is the most important prospect of high Te superconductors （HTS）. Practical HTS samples in various forms have been produced with high critical currents operated at economic cryogenic temperatures. Engineering applications of those HTS materials have been studied with various HTS prototype devices. The applicable HTS materials produced in different forms are verified in this paper with regard to their strong current characterizations, and the HTS applications are summarized along with the HTS prototypes made.     

Metal–Organic Framework Nanosheets: Programmable 2D Materials for Catalysis,Sensing, Electronics,and Separation Applications

Metal–organic framework nanosheets (MONs) have recently emerged as a distinct class of 2D materials with programmable structures that make them useful in diverse applications. In this review, the breadth of applications that have so far been investigated are surveyed, thanks to the distinct combination of properties afforded by MONs. How: 1) The high surface areas and readily accessible active sites of MONs mean they have been exploited for a variety of heterogeneous, photo-, and electro-catalytic applications; 2) their diverse surface chemistry and wide range of optical and electronic responses have been harnessed for the sensing of small molecules, biological molecules, and ions; 3) MONs tunable optoelectronic properties and nanoscopic dimensions have enabled them to be harnessed in light harvesting and emission, energy storage, and other electronic devices; 4) the anisotropic structure and porous nature of MONs mean they have shown great promise in a variety of gas separation and water purification applications; are discussed. The aim is to draw links between the uses of MONs in these different applications in order to highlight the common opportunities and challenges presented by this promising class of nanomaterials.     

Thermoelectric Properties of Skutterudites Co4−x Ni x Sb11.9−y Te y Se0.1

CoSb₃-based skutterudites with substitution of Ni atoms for Co, and substitution of Te and Se atoms for Sb were successfully prepared by solid-state reaction and spark plasma sintering. According to x-ray diffraction analysis the major phase of all the samples had a CoSb₃-type structure, although back-scattered electron images showed that small amounts of impurity phases were present in all the samples. The temperature-dependent transport properties were characterized over the temperature range 300–800 K for all the samples. It was found that appropriate substitution with Ni, Te, and Se effectively improved the power factor and reduced the thermal conductivity. As a result, Ni, Te, and Se-tri-doped CoSb₃ materials with enhanced thermoelectric figures of merit, ZT, were obtained. The highest ZT was greater than 1.1 at high temperature.     

A Micropower Pulsewidth-Modulation?Pulse-Position-Modulation Two-Channel Telemetry System for Biomedical Applications

A novel micropower, two-channel telemetry system, which has been used to transmit the occurrence of the QRS complex of the heart waveform and temperature information, is described. The system employs pulsewidth-modulation (PWM) and pulse-position-modulation (PPM) methods plus a few unique circuits and system-design techniques so that it has the following desirable features. 1) The transmitting unit consumes extremely low power due to low duty cycle and yet delivers high peak power for better receiving. In addition, the unit is compensated (not regulated) for battery voltage variation. 2) By means of adaptive threshold, pulse-width-discrimination and pulse-rate-discrimination networks, the receiving unit is relatively noise free in signal identification. Information in analog and digital form are available at the output for convenience. A prototype system was designed and fabricated. Test results are presented. Due to the availability of the integrated circuits on the market, medical doctors and biologists will be able to duplicate the system if the system-size problem is not severe. Although the design was not trivial, the implementation is quite straightforward. Hence it is believed that device or integrated-circuit manufacturers would be able to implement it in a much more compact form.     

Applications Engineering for Military ＆ Aerospace

Summary： Current functionality demands mean that designers and engineers no longer have the luxury of keeping designs simple and sticking with known technology; in fact, increasingly more designers are now among the first to try new technology, and become innovators rather than followers. Applications engineering services help bridge the safest, most cost-effective designs possible with performance requirements.     

Thermoelectric Performance of AgPb x SbTe20 (x?=?17 to 23) Bulk Materials Derived from Large-Particle Raw Materials

AgPb _x SbTe₂₀ (x?=?17 to 23) bulk materials with nanometer-sized grains were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS) intentionally using large-sized lead and tellurium particles as raw materials to reduce oxygen impurity from surface oxides. It was found that the nominal Pb content in the starting powder mixture greatly affected the thermoelectric (TE) properties of the sintered bulk samples, with excess amount relative to the stoichiometric ratio of AgPb _m SbTe _m+2 less than previously reported. x-Ray diffraction experiments revealed that the lattice parameter increases linearly with increasing Pb content until x?=?20, which corresponds to the optimal nominal Pb content in the starting composition, showing the highest ZT value. A high ZT value of 1.2 at 675?K was achieved in the x?=?20 sample due to its lowest electrical resistivity and reduced thermal conductivity. The present study shows that using large-sized Pb particles containing less oxygen is suitable for fabrication of AgPb _m SbTe _m+2-system TE materials by MA and SPS processes.     

A Fully Differential CMOS Voltage Buffer for?Continuous- and Discrete-Time Applications

This paper presents a new CMOS analog fully differential voltage buffer, with large dynamic range and low harmonic distortion. Its design is based on the use of cross-coupled input differential pairs and internal current feedback. Two design approaches are proposed, with the objective of minimizing power consumption: one for switched-capacitor circuits and the other for Gm-C circuits. Design equations and simulation results are presented as well. Illustrative design examples are developed for a 0.35-μm CMOS technology using a power supply voltage of 2.5 V.