Search results for "Solid"
showing 10 items of 3575 documents
Study of the thermochromic phase transition in CuMo1−xWxO4 solid solutions at the W L3-edge by resonant X-ray emission spectroscopy
2021
Abstract Polycrystalline CuMo 1 − x W x O 4 solid solutions were studied by resonant X-ray emission spectroscopy (RXES) at the W L 3 -edge to follow a variation of the tungsten local atomic and electronic structures across thermochromic phase transition as a function of sample composition and temperature. The experimental results were interpreted using ab initio calculations. The crystal-field splitting parameter Δ for the 5d(W)-states was obtained from the analysis of the RXES plane and was used to evaluate the coordination of tungsten atoms. Temperature-dependent RXES measurements were successfully employed to determine the hysteretic behaviour of the structural phase transition between t…
Phase transitions in Na0.5Bi0.5TiO3-(Sr0.7Bi0.2)TiO3-PbTiO3 solid solutions
2016
ABSTRACTIncreasing of Sr0.7Bi0.2TiO3 concentration in Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions causes increasing of Bi/Na relation and vacancies in the A-site of perovskite structure. In temperature dependence of dielectric permittivity, such a change of composition is reflected by transforming of the frequency-dependent shoulder into a maximum characteristic for relaxor ferroelectrics and diminishing of the frequency-independent maximum characteristic for Na0.5Bi0.5TiO3. Here changes in behavior of dielectric permittivity and polarization are studied if PbTiO3 is added in a certain concentration range of Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions. Changes of the characteristic temp…
Photoluminescence in Er-doped 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions
2020
Photoluminescence and optical second harmonic generation in Er-doped 0.4Na0.5Bi0.5TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions is studied. Earlier, it was shown that upon increasing of PbTiO3 concent...
Spontaneous order in ensembles of rotating magnetic droplets
2019
Ensembles of elongated magnetic droplets in a rotating field are studied experimentally. In a given range of field strength and frequency the droplets form rotating structures with a triangular order - rotating crystals. A model is developed to describe ensembles of several droplets, taking into account the hydrodynamic interactions between the rotating droplets in the presence of a solid wall below the rotating ensemble. A good agreement with the experimentally observed periodic dynamics for an ensemble of four droplets is obtained. During the rotation, the tips of the elongated magnetic droplets approach close to one another. An expression is derived that gives the magnetic interaction be…
Determination of impurity distributions in ingots of solar grade silicon by neutron activation analysis
2017
AbstractIn a series of crystallization experiments, the directional solidification of silicon was investigated as a low cost path for the production of silicon wafers for solar cells. Instrumental neutron activation analysis was employed to measure the influence of different crystallization parameters on the distribution of 3d-metal impurities of the produced ingots. A theoretical model describing the involved diffusion and segregation processes during the solidification and cooling of the ingots could be verified by the experimental results. By successive etching of the samples after the irradiation, it could be shown that a layer of at least 60 μm of the samples has to be removed to get r…
Oxy-nitrides characterization with a new ERD-TOF system
2017
Abstract A new time-of-flight (TOF) camera was installed on Elastic Recoil Detection (ERD) measurement setup on the Tandem Accelerator at Universite de Montreal. The camera consists of two timing detectors, developed and built by the Jyvaskyla group, that use a thin carbon foil and microchannel plates (MCP) to produce the start and stop signals. The position of the first detector is fixed at 18 cm from the target, while the position of the second detector can be varied between 50 and 90 cm from the first detector. This allows to increase time resolution by increasing the distance between the time-of-flight detectors or to increase solid angle by decreasing the distance. Moving the detector …
Normal and relaxor ferroelectric behavior in the Ba1−xPbx(Ti1−yZry)O3 solid solutions
2017
Abstract Polycrystalline samples of Ba 1−x Pb x (Ti 1−y Zr y )O 3 (BPTZ) with x = 0.025 & 0.1 and 0.10 ≤ y ≤ 0.50 have been synthesized by high-temperature solid-state reaction technique. X-ray diffraction reveals the formation of single phase with tetragonal or cubic structure. Dielectric investigations were carried out in the temperature range from 80 to 445 K with frequencies range from 10 2 to 10 6 Hz. A broad dielectric anomaly coupled with the shift of dielectric maxima toward a higher temperature with increasing frequency indicates either a diffuse phase transition or relaxor behavior in some of these ceramics. Whatever lead content, when zirconium is substituted by titanium, T C an…
Spark Plasma Sintering of Metallic Glasses
2019
Spark plasma sintering (SPS) of metallic glasses (MG) can be quite different from sintering crystalline metallic alloys. Indeed, MG behave differently with increasing temperature, as they encounter a glass transition and devitrification. Their shaping can thus be compared to what can be performed on thermoplastic polymers. SPS is a promising way to prepare bulk parts from amorphous powders, since it allows very fast heating and cooling rates. It gives an advantage to avoid or limit devitrification of the amorphous phase upon the thermal cycle. However, diffusion mechanisms, which generally control densification, are activated at temperatures that are not compatible with MG structural integr…
Structural Tuning and Conformational Stability of Aromatic Oligoamide Foldamers
2017
A series of aromatic oligoamide foldamers with two or three pyridine-2,6-dicarboxamide units as their main folding motifs and varying aromatic building blocks as linkers have been synthetized to study the effects of the structural variation on the folding properties and conformational stability. Crystallographic studies showed that in the solid state the central linker unit either elongates the helices and more open S-shaped conformations, compresses the helices to more compact conformations or acts as a rigid spacer separating the pyridine-2,6-dicarboxamide units, which for their part add the predictability of the conformational properties. Multidimensional NMR studies showed that, even in…
A new hydrogen bonding motif involved in self-recognition in the solid state by functionalised macrocycles
2011
Self-recognition within the crystal lattices of three functionalised macrocycles results in the formation of arrays of remarkably similar hermaphroditic pairs of macrocycles. In the case of two of the macrocycles containing acylhydrazine substituents, a hitherto unknown recognition pattern is found in the interaction of the hydrazine moiety with crown-ether oxygen atoms.