Search results for "Atmospheric"
showing 10 items of 5755 documents
Oxidation resistance of Ti 3 AlC 2 and Ti 3 Al 0.8 Sn 0.2 C 2 MAX phases: A comparison
2019
Ti3AlC2 and Ti3Al0.8Sn0.2C2 MAX phase powders are densified using Spark Plasma Sintering technique to obtain dense bulk materials. Oxidation tests are then performed over the temperature range 800-1000°C under synthetic air on the two different materials in order to compare their oxidation resistance. It is demonstrated that, in the case of the Ti3Al0.8Sn0.2C2 solid solution, the oxide layers consist in TiO2, Al2O3 and SnO2. The presence of Sn atoms in
Temperature dependence of luminescence of LiF crystals doped with different metal oxides
2020
Photoluminescence and cathodoluminescence of LiF crystals doped with different binary metal oxides were measured in the wide temperature range of 50-300 K and time interval of 10−8−10−1 s after the nanosecond electron excitation pulse. Both as-grown those and crystals irradiated by an electron beam in range of absorbed dose up to 103 Gy were studied. It is shown that spectral-kinetic characteristics of the luminescence depend on the absorbed dose (type of created/accumulated color centers), the irradiation temperature, the concentration of hydroxyl, which promotes incorporation of the MeO complex (Me: W, Ti, Fe, Li) into the crystal lattice, and the cation-dopants.
Antiferromagnetic NiO thickness dependent sign of the spin Hall magnetoresistance in γ-Fe 2 O 3 /NiO/Pt epitaxial stacks
2019
We study the spin Hall magnetoresistance (SMR) in epitaxial γ–Fe2O3/NiO(001)/Pt stacks, as a function of temperature and thickness of the antiferromagnetic insulating NiO layer. Upon increasing the thickness of NiO from 0 nm to 10 nm, we detect a sign change of the SMR in the temperature range between 10 K and 280 K. This temperature dependence of the SMR in our stacks is different compared to that of previously studied yttrium iron garnet/NiO/Pt, as we do not find any peak or sign change as a function of temperature. We explain our data by a combination of spin current reflection from both the NiO/Pt and γ-Fe2O3/NiO interfaces and the thickness-dependent exchange coupling mode between the …
Raman characterization of Pb2Na1−xLaxNb5−xFexO15 and Pb0.5(5−x)LaxNb5−xFexO15 (0≤x≤1) solid solutions
2011
Abstract The ferroelectric compounds Pb 2 Na 1− x La x Nb 5− x Fe x O 15 and Pb 0.5(5− x ) La x Nb 5− x Fe x O 15 (0≤ x ≤1) with the tungsten bronze type structure have been investigated using Raman spectroscopy. The evolution of the spectra as a function of composition at room temperature is reported. In the frequency range 200–1000 cm −1 three main A 1 phonons around 240 ( υ 1 ), 630 ( υ 2 ) and 816 ( υ 3 ) cm −1 were observed. The broadening of the Raman lines for high values of x originates from a significant structural disorder. This is in good agreement with the relaxor character of these compositions. The lowest-frequency part of the spectra, below 180 cm −1 , reveals a structural ch…
Atomic Layer Deposition of LiF Thin Films from Lithd, Mg(thd)2, and TiF4 Precursors
2013
Lithium fluoride is an interesting material because of its low refractive index and large band gap. Previously LiF thin films have been deposited mostly by physical methods. In this study a new way of depositing thin films of LiF using atomic layer deposition (ALD) is presented. Mg(thd)2, TiF4 and Lithd were used as precursors, and they produced crystalline LiF at a temperature range of 300–350 °C. The films were studied by UV–vis spectrometry, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), time-of-flight elastic recoil detection analysis (ToF-ERDA), and energy dispersive X-ray spectroscopy (EDX). In addition, film adhesion was t…
Annealing behaviour of aluminium-implanted InP
2000
The annealing behaviour of aluminium has been studied in single-crystal InP implanted with 40 and 120 keV 27Al+ ions. The implantation doses were 1 x 1015 and 1 x 1016 cm-2. The aluminium concentration profiles were determined by two techniques, Secondary ion mass spectrometry (SIMS) and the nuclear resonance broadening technique (NRB) which was used for checking purposes. The usability of the SIMS technique for profiling Al rich layers was studied. Significant inconsistencies were observed in the SIMS profiles with the high dose implanted samples. The 120 keV, 1 x 1016 cm-2 implanted samples were subject to annealing in argon atmosphere in the temperature range 380–600°C. Redistribution an…
Comparison of the F-type center thermal annealing in heavy-ion and neutron irradiated Al2O3 single crystals
2018
Abstract The optical absorption and thermally stimulated luminescence of Al2O3 (sapphire) single crystals irradiated with swift heavy ions (SHI) 238U with energy 2.4 GeV is studied with the focus on the thermal annealing of the F-type centers in a wide temperature range of 400–1500 K. Its theoretical analysis allows us to obtain activation energies and pre-exponentials of the interstitial oxygen ion migration, which recombine with both types of immobile electron centers (F and F+ centers). A comparison of these kinetics parameters with literature data for a neutron-irradiated sapphire shows their similarity and thus supports the use of SHI-irradiation for modeling the neutron irradiation.
Lattice sites of diffused gold and platinum in epitaxial ZnSe layers
2000
Abstract The lattice location of diffused gold and platinum in zinc selenide (ZnSe) epitaxial layers was studied using the Rutherford backscattering (RBS) channeling technique. Thin Au and Pt films were evaporated onto ZnSe samples. The Au/ZnSe samples were annealed at 525°C and the residual Au film was removed by etching. Channeling angular scan measurements showed that about 30% of Au atoms were close to substitutional site (displaced about 0.2 A). In the case of the Pt/ZnSe samples the annealing temperatures ranged from 600°C to 800°C. The Pt minimum yields along 〈1 0 0〉 direction were close to the random value, varying from 80% to 90%. The measured Pt angular scans along 〈1 0 0〉 and 〈1 …
Radiation-induced defects in sapphire single crystals irradiated by a pulsed ion beam
2020
Abstract The luminescence and thermal stability of defects formed in α-Al2O3 single crystals after powerful (300 keV) pulsed irradiation with C+/H+ ion beam were investigated. It was found by measuring of optical density, photoluminescence, and pulsed cathodoluminescence that ion irradiation induces both single F-, F+-centers and F2-type aggregate centers. An intense thermoluminescence band with a complex shape was observed in the broad temperature range of 350–700 K, its intensity decreases with increasing of the energy density of the ion beam. The thermal stability of the F-type defects produced in α-Al2O3 after irradiation with a pulsed ion beam is comparable to that in neutron-irradiate…
Relaxation of polarization in (K0.5Na0.5)(Nb0.93Sb0.07)O3 ferroelectric ceramics modified by BaTiO3
2017
ABSTRACTA study of low-frequency relaxation of polarization in conventionally prepared ceramic compounds of (1-x)(K0.5Na0.5)(Nb0.93Sb0.07)O3+xBaTiO3+0.5mol.%MnO2 (x = 0.02, 0.04) examined over a wide temperature range is reported. Anomalous behavior of the temperature dependence of the coercive field Ec(T) is detected in the temperature range of the orthorhombic to tetragonal phase transition. The observed features of polarization are assigned to dynamics of the domain structure at the temperature range of phase coexistence.