Electrochromics for smart windows: Oxide-based thin films and devices

Thermoelectric (TE) materials have the capability of converting heat into electricity, which can improve fuel efficiency, as well as providing robust alternative energy supply in multiple applications by collecting wasted heat, and therefore, assisting in finding new energy solutions. In order to construct high performance TE devices, superior TE materials have to be targeted via various strategies. The development of high performance TE devices can broaden the market of TE application and eventually boost the enthusiasm of TE material research. This review focuses on major novel strategies to achieve high-performance TE materials and their applications. Manipulating the carrier concentration and band structures of materials are effective in optimizing the electrical transport properties, while nanostructure engineering and defect engineering can greatly reduce the thermal conductivity approaching the amorphous limit. Currently, TE devices are utilized to generate power in remote missions, solar-thermal systems, implantable or/wearable devices, the automotive industry, and many other fields; they are also serving as temperature sensors and controllers or even gas sensors. The future tendency is to synergistically optimize and integrate all the effective factors to further improve the TE performance, so that highly efficient TE materials and devices can be more beneficial to daily lives.

https://espace.library.uq.edu.au/view/UQ:722903/UQ722903_OA.pdf

High Performance Thermoelectric Materials: Progress and Their Applications

https://espace.library.uq.edu.au/view/UQ:e38288a/UQe38288a_OA.pdf

High-performance SnSe thermoelectric materials: Progress and future challenge

In this work, triclinic WO 3 nanoplates and WO 3 nanoparticles were comparatively investigated as sensing materials to detect acetone vapors. Single-crystalline WO 3 nanoplates with large side-to-thickness ratios were synthesized via a topochemical conversion from tungstate-based inorganic–organic hybrid nanobelts, and the WO 3 nanoparticles were obtained by calcining commercial H 2 WO 4 powders at 550 °C. The acetone-sensing properties were evaluated by measuring the change in electrical resistance of the WO 3 sensors before and after exposure to acetone vapors with various concentrations. The WO 3 nanoplate sensors showed a high and stable sensitive response to acetone vapors with a concentration range of 2–1000 ppm, and the sensitivity was up to 42 for 1000 ppm of acetone vapor operating at 300 °C. The response and recovery times were as short as 3–10 s and 12–13 s, respectively, for the WO 3 nanoplate sensors when operating at 300 °C. The acetone-sensing performance of the WO 3 nanoplate sensors was more excellent than that of the WO 3 nanoparticle sensors under a similar operating condition. The enhancement of the WO 3 nanoplate sensors in the acetone-sensing property was attributed to the poriferous textures, single-crystalline microstructures and high surface areas of the aggregates consisting of WO 3 nanoplates, which were more favorable in rapid and efficient diffusion of acetone vapors than the WO 3 nanoparticles.

http://www.skl.sic.cas.cn/yjly/nyhj/sj/kycg/201408/W020140814541696209371.pdf

Effects of morphologies on acetone-sensing properties of tungsten trioxide nanocrystals

Nanomaterials for benign indoor environments: Electrochromics for 'smart windows', sensors for air quality, and photo-catalysts for air cleaning

Nanoparticle films of Pd xWO3, with x being 0.01 or 0.12, were made by dual-beam gas evaporation. The stochastic signal component (fluctuation-enhanced signal) originating from resistance fluctuations and the dc resistance (classical sensor signal) were measured during exposure to ethanol and hydrogen gas. For ethanol concentrations exceeding 50 ppm, changes in the resistance fluctuations gave 300 times larger detection sensitivity than changes in the dc resistance. © 2005 Elsevier B.V. All rights reserved.

Comparison of Classical and Fluctuation-Enhanced Gas Sensing with PdxWO3 Nanoparticle Films

Experimental results of gas sensing by thermoelectric voltage fluctuation measurements in gas sensors are presented. The applied sensors consist of monodispersed SnO 2 nanoparticles films, with a mean diameter of 20 nm. The voltage fluctuations in the sensor films were observed with and without external voltage bias and its power density spectrum exceeded at least a thousand times its thermal noise. The power density spectrum of the observed stochastic signal changed in different gases by a factor of three while the change of the sensor resistance was only 2–3%. The stochastic signal observed in the sensor without external voltage bias is caused by the temperature gradient in the film. The results show that thermoelectric fluctuations, without external voltage bias, can be applied for use in gas sensing.

Jesper Ederth

Papers

Comparison of Classical and Fluctuation-Enhanced Gas Sensing with PdxWO3 Nanoparticle Films

Gas sensing by thermoelectric voltage fluctuations in SnO2 nanoparticle films