Search results for "Phase Transition"
showing 10 items of 1281 documents
The structural and dielectric properties of the Na0.96Li0.04NbO3ceramics
2007
Ceramic samples Na0.96Li0.04NbO3 were obtained using ceramic technology. The phase and structural analysis, the microstructure, EDS and EPMA, dielectric and hysteresis loops measurements have been performed. The dielectric and hysteresis loops measurements of Na0.96Li0.04NbO3 have been carried out. The dielectric measurements were performed both without and under axial pressure up to 120 MPa. It was shown that Na0.96Li0.04NbO3 ceramics have orthorhombic symmetry at room temperature and undergo a first order phase transition at a temperature of about 570 K. The axial pressure shifts the phase transition temperature and decreases the hysteresis in field-polarisation and field-strain dependenc…
ScVO4 under non-hydrostatic compression:a new metastable polymorph
2016
Ustedes se ocupan e ver si se puede hacer de acceso público. Podria buscra el preprint al ser algo reciente. Se estudia el comportamiento bajo alta presión del vanadato de scandio, ScVO4, bajo compresión no hidrostática. El estudio se realiza mediante difracción de rayos X en polvo usando radiación sincrotrón. Se detecta una transición no reversible desde la fase zircon a la fase fergusonita alrededor de 6 GPa con una discontinuidad en el volumen de un 10%. La fase fergusonota se puede recuperar como metaestable confirmandose mediante XRD. Las simulaciones ab intio confirman los resultados experimentales. Las propiedades ópticas y la propiedades vibracionales de la fase fergusonita son disc…
Monazite-type SrCrO4 under compression
2016
We report a high-pressure study of monoclinic monazite-type SrCrO4 up to 26 GPa. Therein we combined x-ray diffraction, Raman and optical-absorption measurements with ab initio calculations, to find a pressure-induced structural phase transition of SrCrO4 near 8-9 GPa. Evidence of a second phase transition was observed at 10-13 GPa. The crystal structures of the high-pressure phases were assigned to the tetragonal scheelite-type and monoclinic AgMnO4-type structures. Both transitions produce drastic changes in the electronic band gap and phonon spectrum of SrCrO4. We determined the pressure evolution of the band gap for the low-pressure and high-pressure phases as well as the frequencies an…
Optical and structural study of the pressure-induced phase transition of CdWO$_4$
2017
Physical review / B 95(17), 174105 (2017). doi:10.1103/PhysRevB.95.174105
Phase Transition of Individually Addressable Microstructured Membranes Visualized by Imaging Ellipsometry
2007
The phase transition of individually addressable microstructured lipid bilayers was investigated by means of imaging ellipsometry. Microstructured bilayers were created on silicon substrates by micromolding in capillaries, and the thermotropic behavior of various saturated diacyl phosphatidylcholine (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecoyl-sn-glycero-3-phosphocholine, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) bilayers as well as DMPC/cholesterol membranes was determined by measuring the area expansion and thickness of the bilayer as a function of temperature. We found an increase in the main phase transition temperature T(M) of 2-6 degrees C and a substa…
Smectic C and Nematic Phases in Strongly Adsorbed Layers of Semiflexible Polymers
2017
Molecular dynamics simulations of semiflexible polymers in a good solvent reveal a dense adsorbed layer when the solution is exposed to an attractive planar wall. This layer exhibits both a nematic and a smectic phase (smA for short and smC for longer chains) with bond vectors aligned strictly parallel to the wall. The tilt angle of the smC phase increases strongly with the contour length of the polymers. The isotropic-nematic transition is a Kosterlitz-Thouless transition and also the nematic-smectic transition is continuous. Our finding demonstrates thus a two-dimensional realization of different liquid crystalline phases, ubiquitous in three dimensions, that occurs in a single monomolecu…
Tunable Optical Antennas Using Vanadium Dioxide Metal-Insulator Phase Transitions
2019
Here, we investigate the possibility of exploiting the insulator-to-metal transition in vanadium dioxide (VO2) to tune and optically control the resonances of dipole nanoantennas in the visible near-infrared region. We compare the results obtained in the case of antennas completely made by VO2 with those of previous works and highlight the key role of the substrate to perform dynamical tuning. We also present a highly efficient configuration composed of dipole gold antenna loaded with VO2 and give some general guidelines to optimally exploit phase transitions to tune nanodevices.
Sugar-induced stabilization of the monoolein Pn3m bicontinuous cubic phase during dehydration
2001
To explore the molecular mechanism of the protective function of sugars on cubic lipidic systems, the mesomorphic properties of the monoolein-water system, dehydrated in the presence of a series of sugars, have been studied by osmotic stress experiments. Two bicontinuous inverse cubic structures $(Pn3m$ and $\mathrm{Ia}3d)$ and a lamellar ${L}_{\ensuremath{\alpha}}$ phase form under dehydration in pure water. In sugar solutions, the $\mathrm{Pn}3m$ phase shows an extraordinary stability: as a function of sugar concentration, the lattice parameter decreases to very low values, but no phase transitions occur. Instead, the $\mathrm{Pn}3m$ to $\mathrm{Ia}3d$ phase transition is obtained by equi…
Optical investigation of phase transitions in Di(Tetraethylammonium) pentachloroantimonate(III) [N(C2H5)4]2SbCl5
1997
Abstract Spontaneous changes of linear birefringence in the [N(C2H5)4]2SbCl5 crystal were measured in the temperature range 200–500 K. Presence of two phase transitions at 219 K (monoclinic to orthorhombic) and at 347 K (orthorhombic to tetragonal) was confirmed. Two new phase transitions were found: -at 438 K (tetragonal to tetragonal) and at 467 K -to cubic phase.
Thermochromic Meltable Materials with Reverse Spin Transition Controlled by Chemical Design
2020
International audience; We report a series of meltable FeII complexes, which, depending on the length of aliphatic chains, display abrupt forward low‐spin to high‐spin transition or unprecedented melting‐triggered reverse high‐spin to low‐spin transition on temperature rise. The reverse spin transition is perfectly reproducible on thermal cycling and the obtained materials are easily processable in the form of thin film owing to their soft‐matter nature. We found that the discovered approach represents a potentially generalizable new avenue to control both the location in temperature and the direction of the spin transition in meltable compounds.