Search results for "electric properties"
showing 10 items of 34 documents
Preparation and dielectric properties of (Na 0.5 K 0.5 )NbO 3 ceramics with ZnO and CdO addition
2019
The sintering conditions, phase structure, and electrical properties of the ZnO and CdO doped (Na0.5K0.5)NbO3 (NKN) ceramics were investigated and discussed. All the samples were prepared by a solid state reaction method. The addition of 1 wt% CdO and ZnO as a sintering aid increases the density and lowering the sintering temperature. XRD analysis indicated perovskite structure with monoclinic symmetry. The investigated samples are good quality, the grains are well shaped without a glassy phase. The results of dielectric measurements revealed, that the dielectric properties of NKN based ceramics are stable in the wide temperature range.
Structural phase transition in [(C2H5)4N][(CH3)4N]ZnCl4
2019
The hybrid crystal [(C2H5)4N][(CH3)4N]ZnCl4 was studied using several experimental methods. DSC studies revealed the first order phase transition to the high temperature phase at about 496 K. This phase transition was confirmed in dielectric studies. Optical observation revealed the domain structure appearance characteristic for that of the phase transition between tetragonal and orthorhombic phases. This phase transition shows a lowering of symmetry as in the case of bromide analogs. Additionally, the optical studies showed the appearance of a number of cracks in the sample and in some cases, the samples became milky after cooling from the high temperature to the room temperature phase.
Nanoscale Mapping of the Physical Surface Properties of Human Buccal Cells and Changes Induced by Saliva
2019
International audience; The mucosal pellicle, also called salivary pellicle, is a thin biological layer made of salivary and epithelial constituents, lining oral mucosae. It contributes to their protection against microbiological, chemical, or mechanical insults. Pellicle formation depends on the cells’ surface properties, and in turn the pellicle deeply modifies such properties. It has been reported that the expression of the transmembrane mucin MUC1 in oral epithelial cells improves the formation of the mucosal pellicle. Here, we describe an approach combining classical and functionalized tip atomic force microscopy and scanning microwave microscopy to characterize how MUC1 induces change…
Effect of cobalt doping on the dielectric response of $B_{0.95}Pb_{0.05}TiO_3$ ceramics
2013
Dielectric response of Ba 0.95 Pb 0.05 TiO 3 ceramics doped with 0.1 and 1 wt.% of Co 2 O 3 , synthesized by conven- tional high-temperature method, wa s studied in wide temperature and frequency range. The temperature dependences of the real and the imaginary parts of dielectric permittivity of the ceramics were compared with those of BaTiO 3 and Ba 0.95 Pb 0.05 TiO 3. The addition of Co 3+ ions results in a broadening of dielectric anom- alies related to the transition to p araelectric cubic phase, and the structural transition between the tetragonal and the orthorhombic phases. At low temperatures (125 – 200 K) the dielectric absorp- tion of Co-doped Ba 0.95 Pb 0.05 TiO 3 ceramics was fo…
Differential scanning calorimetry investigation of phase transition in $BaZr_{x}Ti_{1-x}O_{3}$
2009
ABSTRACT Lead-free BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics have been obtained by a conventional method. A single-phase perovskite structure of the ceramics was identified by the X-ray diffraction method. EDS analysis, performed for the individual grains of the tested sample, showed a good homogeneous distribution of all elements throughout the grains. The thermal behaviour of BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics was studied using the Differential Scanning Calorimetry (DSC). Measurements showed the influence of Zr addition on the character of phase transition in the BaTiO3 structure. The results were compared with these ones obtained for pure BaTiO3.
The effect of hydration layers on the anodic growth and on the dielectric properties of Al2O3 for electrolytic capacitors
2014
Hydrous films were grown on high purity and cubicity Al foils for electrolytic capacitors in deionized water, ethylene glycol - deionized water and in glycerol - deionized water for different immersion times. According to the X-ray diffraction patterns the hydration treatment allowed to grow a pseudo boehmite layer on Al surface whose morphology is appreciably affected by the bath composition. Capacitance measurements and photoelectrochemical findings suggest that a more compact barrier layer forms during the immersion in alcohol containing solutions. The hydration in water allowed to save energy and to prepare more blocking oxide films. The beneficial effect of hydration in hot water on th…
Electric conduction in solids: a pedagogical approach supported by laboratory measurements and computer modelling environments
2008
In this paper we present a pedagogic approach aimed at modeling electric conduction in semiconductors, built by using NetLogo, a programmable modeling environment for building and exploring multi‐agent systems. ‘Virtual experiments’ are implemented to confront predictions of different microscopic models with real measurements of electric properties of matter, such as resistivity. The relations between these electric properties and other physical variables, like temperature, are, then, analyzed.
Splitting of surface-related phonons in Raman spectra of self-assembled GaN nanowires
2012
cited By 2; International audience; Micro Raman spectroscopy studies have been performed on GaN nanowires grown by Plasma-Assisted Molecular Beam Epitaxy on Silicon (111) substrate. From the analysis of experimental data, the emergence of a two peaks band located near 700 cm-1 has been attributed to the Raman scattering by surface-related phonons. We have analyzed the surface character of these two modes by changing the dielectric constant of the exterior medium and some experimental parameters. Furthermore, a theoretical model describing the nanowires ensemble by means of an effective dielectric function has been used to interpret the Raman scattering results. Those numerical simulations a…
Local structural investigation of hafnia-zirconia polymorphs in powders and thin films by X-ray absorption spectroscopy
2019
Björn Matthey (Fraunhofer IKTS, Dresden) is acknowledged for providing HfO2 and ZrO2 powders on short notice after DESY’s renowned customs office punished us. Parts of this research were carried out at Petra III at DESY, a member of the Helmholtz Association (HGF). The experiments on single Si:HfO2 thin film samples were performed at the CLAESS beamline at ALBA Synchrotron with the collaboration of ALBA staff. We would like to thank Edmund Welter for assistance (in using beamline P65) and DESY for enabling this research for proposal no. 20160591 and for travel support. T.S. acknowledges the German Research Foundation (DFG) for funding this work in the frame of the project “Inferox” (project…