The Effects of Ba0.85Ca0.15Zr0.1Ti0.9O3 Addition on the Phase, Microstructure, and Thermoelectric Properties of Ca3Co4O9 Ceramics

In this work, the influences of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) addition on phase, microstructure, and thermoelectric properties of Ca3Co4O9 (CCO) were investigated. (1-x)CCO-(x)BCZT ceramics where x = 0, 0.003, 0.005, and 0.010 were fabricated successfully via a conventional solid-state sintering at 1,223 K for 24 hrs. The substitution of BCZT introduced the chemical defects (V''Co, V'''Co, V''Ca) in CCO ceramic, which increased charge carrier concentration and enhanced the electrical conductivity. The presence of Co3+ improved the Seebeck coefficients of CCO ceramic. The thermal conductivity of CCO ceramic decreased when BCZT was added. The addition of BCZT at x = 0.010 promoted the highest thermoelectric power factor (PF~235 mW/mK2), and the highest figure of merit (ZT~0.5) at 800 K, which present this ceramic an alternative p-type oxide thermoelectric for a high-temperature thermoelectric device.

Garment-Integrated Thermoelectric Generator Arrays for Wearable Body Heat Harvesting

Wearable thermoelectric generator arrays have the potential to use waste body heat to power on-body sensors and create, for example, self-powered health monitoring systems. In this work, we demonstrate that a surface coating of a conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT-Cl), created on one face of a wool felt using a chemical vapor deposition method was able to manifest a Seebeck voltage when subjected to a temperature gradient. The wool felt devices can produce voltage outputs of up to 120 mV when measured on a human body. Herein, we present a strategy to create arrays of polymer-coated fabric thermopiles and to integrate such arrays into familiar garments that could become a part of a consumer’s daily wardrobe. Using wool felt as the substrate fabric onto which the conducting polymer coating is created allowed for a higher mass loading of the polymer on the fabric surface and shorter thermoelectric legs, as compared to our previous iteration. Six or eight of these PEDOT-Cl coated wool felt swatches were sewed onto a backing/support fabric and interconnected with silver threads to create a coupled array, which was then patched onto the collar of a commercial three-quarter zip jacket. The observed power output from a six-leg array while worn by a healthy person at room temperature (ΔT = 15 °C) was 2 µW, which is the highest value currently reported for a polymer thermoelectric device measured at room temperature.

The spin-dependent properties of silicon carbide/graphene nanoribbons junctions with vacancy defects

We have designed high-efficient spin-filtering junctions composed of graphene and silicon carbide nanoribbons. We have calculated the spin and charge transport in the junction by non-equilibrium Green’s function formalism combined with the density functional theory to find its spin-dependent electrical conductance, thermal conductance and Seebeck coefficient. In addition, the effect of Si and C atoms vacancies on the transport properties of the junction has been carefully investigated. The enhanced spin-filtering is clearly observed due to the edge and vacancy effects. On the other hand, vacancy defects increase the electrical and spin conductances of the junctions. The results show that the considered junctions are half-metal with reduced thermal conductance which makes them a suitable spin-dependent thermoelectric device. Our results predict the promising potential of the considered junctions for application in spintronic devices.

High Seebeck coefficient in PVD-WS2 film with grain size enlargement

A high Seebeck coefficient of 1.17 × 103 μV/K was achieved using an on-chip thermoelectric device for a WS2 atomic-layer film, which was synthesized by ultra-high vacuum RF-magnetron sputtering as a function of sputtering power. A layered structure in parallel to SiO2/Si substrate was confirmed from the transmission electron microscopy and X-ray diffraction spectra. The grain size and peak intensities of the Raman spectra increase with a decrease in the sputtering power. Accordingly, the resistivity and activation energy also increase. This WS2 film can be used in thermoelectric generators, such as energy harvesters in LSIs and wearable devices.

Analysis of Thermoelectric materials for heating applications in Automobiles

In today’s world with the technological advancements, all that has been considered as slags and waste can be utilized to its maximum therefore attaining sustainability. Thermoelectric devices are now being used in various applications including cooling and heating processes in electronics and automobiles. The choice of materials for these thermoelectric devices are essential in order to determine the parameters such as temperature gradient, thermo emf and total heat dissipated with the help of Seebeck, Peltier and Thomson co-efficients. The elements for the thermoelectric device are arranged by their thermo emf produced in the thermoelectric series. This has been taken into account for the selection of materials for the heating device, analyzed in this article. In certain cold countries, temperature can drop below 10°C, which is very much near its cloud point and pour point of petroleum fuels. Thermoelectric devices will thereby come to use in these places to maintain the temperature above the cloud point of the fuel. This study also focuses on another application of waste heat recovery in automobile engines to produce thermo emf, which can be utilized for small scale electronics in automobiles. In this study, materials are analyzed for the previously mentioned applications.

First-principles study of electronic structures, thermodynamic, and thermoelectric properties of the new Rattling Full Heusler compounds Ba2AgZ (Z = As, Sb, Bi)

The ab initio calculations based on the density functional theory (DFT) using the self-consistent Full potential linearized augmented plane wave (FPLAPW) method were performed to explore the electronic structures, thermodynamic and thermoelectric properties of new rattling Full Heusler alloys Ba2AgZ (Z = As, Sb, Bi). Results showed that the AlCu2Mn-type structure state is energetically the most stable structure. The results show that the electronic property of these cubic Rattling Heusler alloys have a semiconducting behavior with indirect band gaps Eg (L-D). The predicted band gaps were found to be 0.566, 0.548 and 0.433 eV for Z = As, Sb and Bi, respectively. The thermodynamic properties comprising the thermal expansion coefficient, heat capacity, entropy and Debye temperature parameter were evaluated at various pressures from 0 to 15 GPa. Thermoelectric properties of the Ba2AgZ (Z= As, Sb, Bi) materials are additionally computed over an extensive variety of temperature and it is discovered that all compounds exhibit ultralow thermal conductivity, good Seebeck coefficients and large high power factors, thus resulting they are suitable for use in thermoelectric device applications.

Screen-Printed Flexible Thermoelectric Device Based on Hybrid Silver Selenide/PVP Composite Films

In recent years, the preparation of flexible thermoelectric generators by screen printing has attracted wide attention due to easy processing and high-volume production. In this work, we propose an n-type Ag2Se/polymer polyvinylpyrrolidone (PVP) film based on screen printing and investigate the effect of PVP on thermoelectric performance by varying the ratio of PVP. When the content ratio of Ag2Se to PVP is 30:1, i.e., PI30, the fabricated PI30 film has the best thermoelectric property. The maximum power factor (PF) of the PI30 is 4.3 μW·m−1·K−2, and conductivity reaches 81% of its initial value at 1500 bending cycles. Then, the film thermoelectric generator (F-TEG) fabricated by PI30 is tested for practical application; the output voltage and the maximum output power are 21.6 mV and 233.3 nW at the temperature difference of 40 K, respectively. This work demonstrates that the use of PVP combined with screen printing to prepare F-TEG is a simple and rapid method, which provides an efficient preparation solution for the development of environmentally friendly and wearable flexible thermoelectric devices.