Search results for "Diffraction"
showing 10 items of 1584 documents
Transversal thermovoltages of (1 1 9) Bi2Sr2CaCu2O8+δ thin films on vicinal (1 1 0) SrTiO3 substrates
1997
Abstract Biaxial textured (1 1 9) oriented Bi 2 Sr 2 CaCu 2 O 8+δ thin films were fabricated by DC-Magnetron sputtering on vicinal (1 1 0) SrTiO 3 substrates. The crystal orientation and stochiometry of the films were obtained from precise X-ray diffraction measurements in four-circle geometry. According to anisotropic transport measurements, the superconducting transition temperature is approximately 47 K and the normal state resistivities along two perpendicular paths differ by a factor of 13.5. Transversal thermoelectric effects were investigated by measuring thermovoltages transverse to temperature gradients parallel to the surface normal induced by pulsed laser irradiation. At room tem…
Post-spinel transformations and equation of state inZnGa2O4: Determination at high pressure byin situx-ray diffraction
2009
Room-temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa{sub 2}O{sub 4} up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa{sub 2}O{sub 4} undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn{sub 2}O{sub 4}. At 55 GPa, a second transition to the orthorhombic marokite structure (CaMn{sub 2}O{sub 4}-type) takes place. The equation of state of cubic spinel ZnGa{sub 2}O{sub 4} is determined: V{sub 0} = 580.1(9) {angstrom}{sup 3}, B{sub 0} = 233(8) GPa, B'{sub 0} = 8.3(4), and B''{sub 0} = -0.1145 GPa{sup -1} (implied value); showing that ZnGa{sub 2}O{sub 4} is one of the less comp…
Epitaxial growth and thermoelectric properties of TiNiSn and Zr0.5Hf0.5NiSn thin films
2011
Abstract Due to their exceptional thermoelectric properties Half-Heusler alloys like MNiSn (M = Ti,Zr,Hf) have moved into focus. The growth of single crystalline thin film TiNiSn and Zr 0.5 Hf 0.5 NiSn by dc magnetron sputtering is reported. Seebeck and resistivity measurements were performed and their dependence on epitaxial quality is shown. Seebeck coefficient, specific resistivity and power factor for Zr 0.5 Hf 0.5 NiSn at room temperature were measured to be 63 μV K − 1 , 14.1 μΩ m and 0.28 mW K − 2 m − 1 , respectively. Multilayers of TiNiSn and Zr 0.5 Hf 0.5 NiSn are promising candidates to increase the thermoelectric figure-of-merit by decreasing thermal conductivity perpendicular …
Fine grain barium titanate: ferroelectric domains and X-ray diffraction diagram
2002
Through three different studies using various kinds of BaTiO/sub 3/ samples: as a powder while heating over the Curie temperature; as a green ceramic as a function of the forming pressure; as a ceramic while applying a D.C. field. It is shown how X-ray diffraction is able to give information about the evolution of the 90/spl deg/ ferroelectric domain microstructure.
Static and dynamic properties of low-temperature order in the one-dimensional semiconductor(NbSe4)3I
2016
We investigated static and dynamic lattice properties in a quasi-one-dimensional charge-ordered semiconductor ${({\mathrm{NbSe}}_{4})}_{3}\mathrm{I}$ by using Raman, femtosecond pump-probe spectroscopy and x-ray diffraction. In addition to a well-documented pseudo-Jahn-Teller ferrodistortive structural transition at ${T}_{C}=274$ K, where the displacements of Nb ions lead to ferroelectric (FE) in-chain polarization with opposite direction in adjacent chains, all methods suggest an additional lowering of symmetry at ${T}^{*}\ensuremath{\approx}160$ K. Although antiferroelectric (AFE) phase is partially formed at ${T}_{C}$, our results consistently point to an enhancement of the interchain or…
Raman scattering as a tool for the evaluation of strain inGaN∕AlNquantum dots: The effect of capping
2007
The strain state of $\mathrm{Ga}\mathrm{N}∕\mathrm{Al}\mathrm{N}$ quantum dots grown on $6H\text{\ensuremath{-}}\mathrm{Si}\mathrm{C}$ has been investigated as a function of AlN capping thickness by three different techniques. On the one hand, resonant Raman scattering allowed the detection of the ${A}_{1}(\mathrm{LO})$ quasiconfined mode. It was found that its frequency increases with AlN deposition, while its linewidth did not evolve significantly. Available experiments of multiwavelength anomalous diffraction and diffraction anomalous fine structure on the same samples provided the determination of the wurtzite lattice parameters $a$ and $c$ of the quantum dots. A very good agreement is …
Strain‐induced compression of smectic layers in free‐standing liquid crystalline elastomer films
2005
The deformation of oriented smectic liquid crystal elastomer films with smectic layers parallel to the film surface was studied using optical reflectometry and small angle X‐ray diffraction. Reflectometry data show that in the chosen material, in‐plane strain causes a change in the optical thickness of the free‐standing films. Small angle X‐ray scattering was used to explore the molecular origin of this effect. The X‐ray scattering data confirm that the change in optical thickness originates from the compression of the individual smectic layers. The measured Poisson ratio in the smectic A and C* phases is close to ½, in contrast to the smectic elastomers investigated earlier by Nishikawa et…
Density variations in liquid tellurium: Roles of rings, chains and cavities
2010
Liquid tellurium has been studied by density-functional/molecular-dynamics simulations at 560, 625, 722, and 970 K and by high-energy x-ray diffraction (HEXRD) at 763 K and 973 K. The HEXRD measurements agree very well with earlier neutron-scattering data of Menelle et al. The density maximum near the melting point (722 K) reflects the competition between twofold and threefold local coordination, which results in chain formation and changed ring statistics at lower $T$, and the variation with $T$ of the volume of cavities ($26--35\text{ }\mathrm{%}$ of the total). A higher-order gradient expansion of the exchange-correlation functional is needed to describe structural details. Changes in th…
X-Ray diffraction diagram evolution of a BaTiO3ceramic under an electric field
1994
Abstract The X-ray diffraction diagrams of a coarse grained pure BaTiO3 ceramic have been recorded as a function of the applied electric D.C. field. This field was perpendicular to the X-ray incoming surface. The experimental device used allows to record diffraction diagrams while the electric field step by step increases. The intensity ratio of the 002 line over the 200 line increases with the applied electric field. The evolution of the X-ray diffraction line intensities is in correlation with the first polarization curve of the ferroelectric ceramic. These results evidence a contribution of the 90° ferroelectric domains pattern to the X-ray diffraction diagram of BaTiO3.
Site-specific atomic order and band structure tailoring in the diluted magnetic semiconductor (In,Ga,Mn)As
2021
Physical review / B 103(7), 075107 (1-13) (2021). doi:10.1103/PhysRevB.103.075107