Al-doped ZnO films were deposited onto SiO 2 /Si substrates by rf magnetron sputtering system as a CO gas sensor. The dependence of the thin film thickness on CO gas sensing properties was investigated, where the film thickness was varied by controlling the deposition time. The structure of the deposited ZnO:Al films was determined by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The CO gas sensing properties were determined by in situ measurement for surface resistance of the thin film as a function of film thickness, different atmosphere, and operation temperature. It was shown that the films were flat and smooth with (0 0 0 1) preferred orientation. The grain size was increased as the film thickness was increased during deposition. Here, the CO gas sensing properties were relative to the structural characteristics where the maximum sensitivity of 61.6% was obtained at 65 nm film thickness for the operation temperature of 400 °C.

The effects of thickness and operation temperature on ZnO:Al thin film CO gas sensor

The Hall effect has been measured for ultrafine particle films of tin oxide (particle size 50–200 A) in contact with reducing gases. Both the carrier concentration and mobility increased with an increasing concentration of reducing gas. As a result, conductivity, the product of the carrier concentration and mobility, shows a large gas concentration dependence. This means the ultrafine particle films are highly sensitive to gases. The variation of the carrier mobility with the gas concentration is interpreted in terms of a model in which the width of a long, thin channel, determined by particle size and Debye length, increases with a decrease in the number of O− ions desorbed by a chemical reaction with the reducing gases.

Hall measurement studies and an electrical conduction model of tin oxide ultrafine particle films

Perovskite-type oxides as ethanol sensors

Chemical reactions between the superior perovskite oxide-ion conductor Sr- and Mg-doped LaGaO 3 (LSGM), CeO 2 , and NiO have been studied by powder X-ray diffraction. The results showed that an extensive reactivity occurs as a result of La migration driven by a gradient of La chemical activity. La migration across the LSGM/electrode interfaces in a fuel cell leads to the formation of resistive phases at the interface, either LaSrGa 3 O 7 or LaSrGaO 4 . Use of 40 mol % La 2 O 3 -doped CeO 2 as an interlayer between anode and electrolyte as well as in the NiO-containing anode prevents all reactions found. Consequently, the air-H 2 cell maximum power density was increased to nearly 900 mW/cm 2 at 800°C with a 600 μm thick LSGM electrolyte. No sign of degradation was observed at 800°C over 2 weeks for an interlayered cell under a loading current density of 250 mA/cm 2 .

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Increasing Power Density of LSGM-Based Solid Oxide Fuel Cells Using New Anode Materials

Epitaxial LaNiO3(LNO) thin films on LaAlO3(LAO), SrTiO3(STO), and YSZ are grown by pulsed laser deposition method at 350 mTorr oxygen partial pressure and 700 °C substrate temperature. As‐deposited LNO films are metallic down to 10 K. c‐axis oriented YBa2Cu3O7 (YBCO) films were grown on LNO/LAO as well as LNO/STO surfaces without affecting superconducting transition temperature of YBCO. Textured LNO thin films were grown on c‐axis oriented YBCO/STO and YBCO/YSZ . Transport measurements of these bilayer films showed that LNO is a good metallic contact material for YBCO.

Epitaxial metallic LaNiO3 thin films grown by pulsed laser deposition

The perovskite-type compounds La1-xMxNiO3 (M: Ca, Sr and Ba) were synthesized and their crystallographic, electric and thermochemical properties were investigated. The regions of perovskite formation were determined. The solubility limits or alkaline earth elements into La sites are around 5% for Sr and Ba, and less than 1% for Ca. The charge compensation of divalent ion substitution into a trivalent La ion site takes place by the formation of oxygen ion vacancies. Lanthanoid elements other than La did not form perovskite-type oxides. The compound LaNiO3 undergoes a rhombohedral-cubic transition at 940?C and decomposes above 1120?C. Resistivity of LaNiO3 is 9?10-3 ?cm at room temperature and increases as the temperature is raised.

https://iopscience.iop.org/article/10.1143/JJAP.14.330/pdf

Hidehito Obayashi

Papers

Some Crystallographic, Electric and Thermochemical Properties of the Perovskite-Type La1-xMxNiO3(M: Ca, Sr and Ba)