Search results for "Electronic engineering"
showing 10 items of 8802 documents
Synthesis of ZnO–Ag2CO3–Fe3O4@rGO core–shell structure: magnetically separable photocatalyst for degradation of MB using the Box–Behnken design
2020
In this work, a simple microwave method was utilized to prepare ZnO sheet linked with Fe3O4@rGO core–shell and of Ag2CO3 through formation of the quadri-photocatalytic with high activity. The microstructure, morphology, spectroscopic, and magnetic characteristics of the prepared samples were assessed using XRD, SEM, PL, TEM, FT-IR, DLS, and VSM analysis. The photocatalytic activity of the material was evaluated for photodegradation of methylene blue dye under the UV and visible light with home-made photoreactor. The response surface method in a Box–Behnken design was utilized to design the experiments. The parameters affecting the efficiency of the degradation including, pH (5–9), photocata…
Thermal expansion and polarization of (1-x)PNN-xPT solid solutions
2019
The paper presents the results of detailed studies of the thermal expansion of (1-x)PbNi1/3Nb2/3O3-xPbTiO3 solid solutions with x = 0-0.8. The anomalous and lattice contributions to deformation and...
Temperature Coefficients of Crystal Defects in Multicrystalline Silicon Wafers
2020
This article investigates the influence of crystallographic defects on the temperature sensitivity of multicrystalline silicon wafers. The thermal characteristics of the implied open-circuit voltage is assessed since it determines most of the total temperature sensitivity of the material. Spatially resolved temperature-dependent analysis is performed on wafers from various brick positions; intragrain regions, grain boundaries, and dislocation clusters are examined. The crystal regions are studied before and after subjecting the wafers to phosphorus gettering, aiming to alter the metallic impurity concentration in various regions across the wafers. Most intragrain regions and grain boundarie…
Anomalies of dielectric properties and conductivity in single domain LiNbO3:Zn crystals
2016
ABSTRACTA study of the temperature dependence of dielectric constant, conductivity, and piezoelectric modulus in the single-domain state of LiNbO3 crystals modified by Zn admixture at threshold concentration is reported. Unipolarity of the LiNbO3:Zn crystals is observed to increase after treatment of brand-new samples by high-temperature electro-diffusion annealing and by subsequent high-temperature annealing of short-circuited samples. The observed effects are explained as a result of meta-stable residual domains collapsing at high temperature the collapse being assisted by disintegration of charged clusters stabilizing domain walls. The rise of unipolarity is accompanied by anomalies on t…
Half-Heusler superlattices as model systems for nanostructured thermoelectrics
2015
The efficiency of thermoelectric materials is directly related to the dimensionless figure of merit , therefore, one of the means to improve ZT is to reduce the thermal conductivity. Our research focuses on half-Heusler superlattices (SLs) and the relationship between the SL period and the thermal conductivity. The cross-plane thermal conductivity of DC-sputtered TiNiSn/HfNiSn SLs was measured by the 3 method at room temperature and a clear reduction of was achieved for all SL periods, in particular for periods smaller than 20 nm. Moreover, the thermal conductivities of TiNiSn and HfNiSn single films display reduced values compared to the literature data for bulk materials. Furthermore, we …
Electronic structure and magnetic order in Cu Zn(1−)O: A study GGA and GGA + U
2019
Abstract Based on density functional theory within GGA formalism, first-principles calculations were performed in order to study the structural, electronic, and magnetic properties of Cu-doped ZnO compound with dopant concentrations x = 0.028, 0.042, 0.056, and 0.125. It was found that CuxZn(1−x)O is ferromagnetic for both the closest and farthest impurity distances, but it is more stable energetically for the closest one. For all concentrations we obtained nearly half − metallic behavior. The calculations show that two substitutional Cu atoms introduce a magnetic moment of about 2.0 μB for all dopant concentrations. The results indicate that the magnetic ground state originates from the st…
Half-Heusler materials as model systems for phase-separated thermoelectrics
2015
Semiconducting half-Heusler compounds based on NiSn and CoSb have attracted attention because of their good performance as thermoelectric materials. Nanostructuring of the materials was experimentally established through phase separation in (T1−x′Tx″)T(M1−yMy′) alloys when mixing different transition metals (T, T′, T″) or main group elements (M, M′). The electric transport properties of such alloys depend not only on their micro- or nanostructure but also on the atomic-scale electronic structure. In the present work, the influence of the band structure and density of states on the electronic transport and thermoelectric properties is investigated in detail for the constituents of phase-sepa…
Tetragonal Heusler Compounds for Spintronics
2013
With respect to the requirements of spin torque transfer (STT) materials, one the most promising materials families are the tunable tetragonal Heusler compounds based on Mn2YZ (Y=Co,Fe,Ni,Rh,...; Z=Al, Ga, Sn). They form the inverse cubic Heusler structure with three distinct magnetic sublattices, which allows a fine tuning of the magnetic properties. Starting with the stoichiometric Mn3Ga compound, we explored the complete phase diagram of Mn3-xYxZ (Y=Co, Fe, Ni and Z=Ga ). All series exhibit thermally stable magnetic properties. As we demonstrate, Mn3-xFexGa series, which are tetragonal over the whole range of compositions, are good as hard magnets, whereas magnetically more weak Mn3-xNix…
Space Charge Measurement under DC and DC Periodic Waveform
2018
In High Voltage systems, Partial Discharges (PDs) monitoring are one of the main diagnostic instrument to evaluate the reliability of the apparatus. Under Alternating Current (AC) stress, PDs detection and recognition techniques are well consolidated. On the contrary, the monitoring of PDs under Direct Current (DC) stress is difficult due to complexities related to the nature of the phenomenon, which cause the beginning of PDs events in proximity of the dielectric breakdown. This problem has been partially overcome by using a continuous Periodic waveform (DCP) with positive average value, as described in a recent published work. Under DC stress, another degradation factor is the Space Charg…
The effects of the additive of Eu ions on elastic and electric properties of BaTiO3ceramics
2016
ABSTRACTThe BaTiO3 and BaTiO3+X%wt.Eu2O3 (X = 1, 2, 3) ceramics were prepared by a solid phase reaction. The structural and morphology studies were carried out by means of an X-ray diffraction technique and scanning electron microscopy, respectively. Elastic moduli were determined with the use of an ultrasonic method. The dielectric permittivity (ϵ′) and tanδ as a function of composition and temperature were investigated. The increasing concentration of Eu ions leads to a slight shift of the Curie temperature and changes the characteristics of ϵ′ and tanδ. The structural, mechanical and dielectric properties of the BTEX ceramics were discussed in terms of microstructure and dopants contents.