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showing 10 items of 2987 documents
Thermostimulated luminescence of plasma electrolytic oxidation coatings on 6082 aluminium surface
2019
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/12 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. Authors are grateful to R. Ignatans for measurements and analysis of XRD spectra and ElGoo Tech ltd. for providing PEO equipment.
Non-destructive technique to detect local buried defects in metal sample by scanning microwave microscopy
2012
International audience; Based on the skin effect, our recent developments using scanning microwave microscopy lead to propose a non-destructive method to detect located buried defect in metal samples like stainless steel. A 3D tomography is possible by taking advantage of microwave measurement, using a vector network analyzer in bandwidth frequencies, and the nanometer resolution positioning capabilities with atomic force microscopy. At each used frequency, an incident electromagnetic wave is sent to the sample and the reflected wave gives information on a specific depth layer in the material. With diagnostic tools of nanotechnologies (SEM. AFM, etc.), different stainless steel samples (fro…
Aging and Memory Effects in PLZT 8/65/35 Ceramics Modified with 3d Transition-Metal Ions
2015
The temperature and frequency dependencies of the dielectric susceptibility in relaxor electro-optical PLZT 8/65/35 modified with 3d transition-metal ions (Mn, Fe, Co, Ni) measured to study the aging and memory effects are reported. The studies of aging at room temperature show that 3d admixtures (Me) in PLZT 8/65/35 ceramics at small to medium concentration range (Me < 1.0 wt.%) change the depth of dispersion, the aging amplitude and the temperature range of the memory effect. At admixture concentrations Me →1.0 wt% the aging and memory effect are significantly reduced (or eliminated).The obtained results suggest that aging effects are determined by two substantial acceptor effects of the …
Relaxor ferroelectric PbSc1/2Nb1/2O3—PbZn1/3Nb2/3O3— PbMg1/3Nb2/3O3ceramics
2000
Abstract Original ternary solid solutions PbSc1/2Nb1/2O3 — PbZn1/3Nb2/3O3-PbMg1/3Nb2/3O3 (PSN-PZN-PMN) have been synthesized by solid state reaction from oxides. Ceramic samples have been obtained by both conventional and hot pressing techniques. The density of the obtained hot pressed ceramics reaches 98% of the value calculated from X-ray data. Dense, high quality samples of pure PZN and compositions containing over 0.8 molar parts of PZN could not be obtained — porosity was up to 10% and they were mainly comprised of the cubic pyrochlore phase. Density, porosity, water absorbtivity, and dielectric permittivity and dissipation factor of the ceramic samples have been measured. Data of diff…
Dielectric Dispersion and Ion Conductivity in High-Pressure LixNaw1-xNbO3Solid Solutions
2009
Thermal behaviour and dispersion of dielectric permeability and thermal behaviour of conductivity measured in ferroelectric ceramic solid solutions of Li x Na 1−x NbO 3 (x = 0.17, 0.25) synthesized at high pressure and possessing extended region of homogeneity are reported. The Li x Na 1−x NbO 3 (x = 0.17, 0.25) solid solutions of perovskite structure are found to be super-ionic conductors at rather low temperatures O ≥ 400 K. Dielectric dispersion and anomalous behaviour of dielectric permeability are observed in the thermal range of super-ionic conductivity corresponding to structural transformations in the high-pressure solid solutions.
Conductivities and silver electrode polarization resistance of solid electrolyte ceramics from ZrO 2 -Y 2 O 3 powder synthesized in air plasma
1998
Ceramic specimens have been obtained from the powder of ZrO2-7.5 mol% Y2O3 having a specific surface area of 30 m2/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties. The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm3. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the tempera…
Luminescence of X-ray induced radiation defects in modified lithium orthosilicate pebbles with additions of titanium dioxide
2017
The authors greatly acknowledge the technical and experimental support of O. Leys, M. H. H. Kolb, and R. Knitter (Karlsruhe Institute of Technology, Germany). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Economics”.
Permeability measurements in cobalt ferrite and carbonyl iron powders and suspensions
2002
Abstract Magnetic permeability data of cobalt ferrite and carbonyl iron suspensions are discussed. Using an induction method, the relative differential permeability, μr,dif, was measured as a function of the internal magnetic field for different volume fractions of the solid phase. In the case of cobalt ferrite suspensions, the μr,dif−H curve was obtained for a first increasing ramp of magnetic field (data series “1”), a decreasing ramp (data series “2”), and the second increasing one (data series “3”). Series “1” showed a maximum in the μr,dif−H trend that did not appear in series “2” and “3”. Furthermore, the data in series “2” and “3” are always below those in series “1”. The latter beha…
The Influence of Morphological Aspects in the Reaction Pathway and Superconductive Properties of Bi2223-Ca2CuO3 Ceramic Composites
1994
ABSTRACTA variation of the solid-state matrix technique has been developed as a procedure for the preparation of 2223 bismuth superconducting phases [(Bi,Pb)2Sr2Ca1-nCunO4+2n, n=3]. The adequate processing of samples of nominal compositions 2223+x 0021, obtained both by this procedure and by the polymer matrix method, has allowed the modification of the microstructure of the calcium copper excess, with no noticeable change in that of the 2223 grains. The study of the phase evolution in the processing of the samples has shown that the formation rate of the 2223 phase is faster when the particle size of the calcium cuprate is smaller. A dependence of the intergranular superconducting properti…
Au Adsorption on Regular and Defected Thin MgO(100) Films Supported by Mo
2007
Using density functional theory we studied systematically a Au atom adsorption on a Mo-supported regular and defected ultrathin MgO film with 1 to 5 ML thickness. On Mo(100) grown regular MgO Au prefers to adsorb at a hollow site instead of an O site found for single-crystal MgO. The metal support also enhances Au adsorption energy in agreement with the earlier theoretical results. Adsorption energy decreases with increasing film thickness being, however, even in the case of 5 ML thick MgO much higher than that on single-crystal MgO. The Bader analysis was performed to estimate the spatial distribution of charge in different cases. The results show charge transfer (0.7−0.8 e) to the Au atom…