In the present work, a hydrogen gas sensor of moderate sensitivity utilizing multiwalled carbon nanotubes partially decorated with zinc oxide nanoparticles (MWCNTs/ZnO) has been fabricated. To further enhance its sensitivity, nanoparticles of platinum (Pt) metal have been deposited via a sputtering technique on the MWCNTs/ZnO layer. The sensing materials were characterized by scanning electron microscopy (SEM), Raman and x-ray diffraction (XRD) spectroscopy. The MWCNTs/ZnO/Pt sensor shows a low recovery time of ~78 s and good repeatability when exposed to a 0.05% concentration of H2 gas at room temperature. Moreover, the sensitivity achieved for the MWCNTs/ZnO/Pt sensor is 4.2% as compared to 1.6% for MWCNTs/ZnO for 1% concentration of H2 gas. To the best of our knowledge, such a low concentration of H2 gas detection is reported for the first time using a MWCNTs/ZnO/Pt hybrid nanostructure at room temperature.
Ca-doped LaInO 3 (LCI) has been synthesized by conventional solid-state reaction method. The structural features were investigated by X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The structural investigation indicated that Ca 2+ dopants occupy both A-and B-sites in ABO 3 (La 1-x In x O 3-δ ). The solid solubility limit has been observed up to x = 0.10 for La 1-x Ca x InO 3-δ system. In addition, the Raman band softening has been observed with Ca-doping. The impedance spectroscopy shows that 10 mol% of Ca-doped LaInO 3 possesses the highest conductivity of the order of 1.64 mS cm −1 at 700°C among all investigated samples. The activation energy of doped samples lies within the range of 0.69-0.86 eV, which indicates that the conductivity in the reported samples is mainly contributed by ion transportation. SEM analysis supports the well-packed grains in the sintered samples.
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