Maxwell-Wagner Relaxations in Ca-, Sm- and Nd-doped Ceria

Doped ceria, i.e. Ce1-xMxO2-d with M being dopant metal, has been a focus of great attention for SOFCs due to its high oxygen conduction. In the past literature, the dielectric relaxations in these materials have been ascribed to be caused by defect associates (MCeʺ-Vö) possessing different MCeʺ and Vö distances. But we believe that with changing measurement and analysis techniques it is necessary to invest our time to re-examine the already reported materials and to again take a detailed investigation of the underlying phenomenon behind their dielectric relaxations. Thus, we have used solid-state reaction to prepare Ce1-xMxO2-δ with M=Ca, Sm, and Nd in x=0.1, 0.2, and 0.3 ratios, respectively. The as-prepared and post annealed samples were tested for dielectric properties from 300-1080 K with varying frequencies. The low-temperature relaxation (R1) was argued to be a Maxwell-Wagner relaxation caused by humidity sensitivity. The high-temperature relaxation (R2) was ascribed to be caused by hopping motion of oxygen vacancies. This fact was also supported by detailed analysis of impedance spectra. While, according to the previous reports this relaxation is because of oxygen-vacancy-dopant defect pair.

Study the Characteristics of the nanocomposite prepared by two steps laser ablation in liquids

In the present work, structural, optical, electrical and sensing properties have been studied for the (TiO2/rGO) nanocomposite prepared by the pulse laser ablation method in the liquid, where the Nd-Yag laser was used, and the two wave pulses (1064-532) and 300mJ, which were deposited on glass bases , The structural properties have been investigated by X-Ray diffraction technique analysis and morphological by atomic force microscope (AFM), The particle size of the membranes is less in the films prepared using wavelength (1064) than in the prepared films using wavelength (532). The optical properties of the nanocomposites have been determined by using the optical transmittance measurements in the spectral region from (300- 1100) nm. Electrical properties such as I-V properties was also studied. sensing properties measurements showed good Humidity sensitivity within the range (20-80) % RH.

An Optical Fiber Sensor Coated with Electrospinning Polyvinyl Alcohol/Carbon Nanotubes Composite Film

A fiber-optics tapered sensor that is covered by an electrospinning polyvinyl alcohol (PVA) nanofiber film, is demonstrated to measure humidity and temperature simultaneously. A section multi-mode fiber (MMF) was sandwiched between two leading-in and out single mode fibers (SMFs), which was further tapered down to 29 μm to promote the humidity sensitivity of the sensor. A thin layer of electrospinning PVA nanofiber film was uniformly coated on the MMF taper region by electrospinning technology. In order to promote the humidity sensitivity and mechanical strength of electrospinning nanofibers, the carbon nanotubes (CNTs) were mixed into PVA to formed PVA/CNTs composite nanofiber film. A Fiber Bragg Grating (FBG) was cascaded with the humidity sensing fiber to monitor the ambient temperature simultaneously. The addition of CNTs effectively eliminated the cracks on the electrospinning nanofiber and made it more uniform and smoother. As experimental results show, the humidity sensitivity of the sensor with PVA/CNTs film was 0.0484 dB/%RH, an improvement of 31.16% compared to that of the sensor with PVA film, for which sensitivity is 0.0369 dB/%RH. The nanofiber humidity-sensitive film constructed using electrospinning had a satisfactory humidity response, special 3D structure and extensive application prospect.