Search results for "Diffraction"
showing 10 items of 1584 documents
Synthesis of a novel zeolite through a pressure-induced reconstructive phase transition process
2013
et al.
Experimental and theoretical study of dense YBO3 and the influence of non-hydrostaticity.
2021
[EN] YBO3 is used in photonics applications as a host for red phosphors due to its desirable chemical stability, high quantum efficiency and luminescence intensity. Despite its fundamental thermodynamic nature, the isothermal bulk modulus of YBO3 has remained a contentious issue due to a lack of comprehensive experimental and theoretical data and its vibrational modes are far from being understood. Here, we present an experimental-theoretical structural and vibrational study of YBO3. From structural data obtained from synchrotron X-ray diffraction data and ab initio calculations, we have determined the YBO3 bulk modulus, isothermal compressibility tensor and pressure-volume (P-V) equation o…
Low temperature structural transformations on the (001) surface of SrTiO 3 single crystals
2020
This work was supported by the Ministry of Education and Science of Ukraine under the contract M/51–2019 within the framework of the Program of Ukrainian–Latvian Scientific and Technical Cooperation and Latvian–Ukranian Grant LV-UA/2018/2. Authors are indebted to L.L. Rusevich, G. Zvejnieks, V.P. Gnezdilov and A. Glamazda for stimulating discussions.
Crystallographic changes and thermal properties of lanthanum?strontium ferromanganites between RT and 700 �C
2005
Abstract X-ray powder diffraction was used to determine the crystallographic changes between room temperature (RT) and 700 °C of the (La 0.8 Sr 0.2 )(Mn 1− y Fe y )O 3± δ perovskites with y =0.2, 0.5, 0.8, 1 which can be considered as possible cathode materials for the ITSOFCs. For y =0.2, the rhombohedral symmetry was preserved in the whole temperature range. For y =1, a transition from orthorhombic to rhombohedral symmetry occurred at 290 °C. The compounds with y =0.5 and 0.8 were found to be diphasic at RT by combination of both rhombohedral and orthorhombic symmetries. They became only rhombohedral at 80 and 160 °C, respectively. This reversible transition is discussed in terms of iron …
Novel octahedral tilt system a + b + c + in (1 − x)Na0.5Bi0.5TiO3–xCdTiO3 solid solutions
2017
This work has been supported by National Research Program in the framework of project “Multifunctional Materials and composites, photonics and nanotechnology (IMIS2)”.
Structural Signatures of Type IV Isotherm Steps: Sorption of Trichloroethene, Tetrachloroethene, and Benzene in Silicalite-I
2002
We have investigated by in situ neutron diffraction the structural properties of C2HCl3, C2Cl4, and C6D6 sorbed phases in silicalite-1. Our motivation is to correlate the structure of these three confined species to the fact that their adsorption isotherms are characterized by no step, one step, and two steps, respectively. From our detailed neutron diffraction investigation, we deduce that the adsorption isotherm steps are not signatures of phase transitions but are correlated to the different adsorption stages observed during the silicalite-1 loading. For C6D6, such a loading is a three stage process (the C6D6 molecules fill successively, the intersections, then the straight channels and …
Neutron diffraction experiments on UCu4+xAl8−x
1992
Abstract Neutron diffraction experiments are reported on UCu4+xAl8−x for concentrations 0.1≤ x ≤1.9 and temperatures 1.6 K≤T≤300 K. For x ≤ 1 these compounds undergo antiferromagnetic phase transitions into a collinear AF I-type structure. with the magnetic moments aligned along the tetragonal c-axis and alternating order within the a−b planes. With increasing concentration the ordering temperatures decrease and moment compensation due to a Kondo-type interaction develops for x>1.
LaAg x In1?x
1980
The phonon dispersion of LaAg x In1−x (x=1, 0.89, 0.8) has been studied by inelastic neutron scattering in the cubic high temperature phase. A soft mode behaviour was observed at theM-point. The doubling and the cubic to tetragonal deformation of the elementary cell was observed through the phase transition. The measurements of the elastic constants were extended to 450 K and their magnetic field dependence was investigated.
Experimental and Theoretical Investigations on Structural and Vibrational Properties of Melilite-Type Sr2ZnGe2O7 at High Pressure and Delineation of …
2015
We report a combined experimental and theoretical study of melilite-type germanate, Sr2ZnGe2O7, under compression. In situ high-pressure X-ray diffraction and Raman scattering measurements up to 22 GPa were complemented with first-principles theoretical calculations of structural and lattice dynamics properties. Our experiments show that the tetragonal structure of Sr2ZnGe2O7 at ambient conditions transforms reversibly to a monoclinic phase above 12.2 Gpa with similar to 1% volume drop at the phase transition pressure. Density functional calculations indicate the transition pressure at, similar to 13 GPa, which agrees well with the experimental value. The structure of the high-pressure mono…
Exploring the high-pressure behavior of the three known polymorphs of BiPO4: Discovery of a new polymorph
2015
We have studied the structural behavior of bismuth phosphate under compression. We performed x-ray powder diffraction measurements up to 31.5 GPa and ab initio calculations. Experiments were carried out on different polymorphs: trigonal (phase I) and monoclinic (phases II and III). Phases I and III, at low pressure (P < 0.2-0.8 GPa), transform into phase II, which has a monazite-type structure. At room temperature, this polymorph is stable up to 31.5 GPa. Calculations support these findings and predict the occurrence of an additional transition from the monoclinic monazite-type to a tetragonal scheelite-type structure (phase IV). This transition was experimentally found after the simultaneo…