Materials Literature
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Argon gas was trapped at high pressure within hollow carbon tubes grown in vapor that have an outer diameter of between 20 and 150 nanometers. The gas was forced into the tubes by hot isostatically pressing (HIPing) the carbon material for 48 hours at 650°C under an argon pressure of 170 megapascals. Energy dispersive…
The electric field induced phase transition behavior of lead lanthanum zirconate titanate stannate (PLZTS) ceramics was investigated. PLZTS undergoes a tetragonal antiferroelectric (AFETet) to rhombohedral ferroelectric (FERh) phase transition with the application of an electric field. The volume increase associated w…
Through the use of relations analogous to that of the Rayleigh law, it is demonstrated that the ac electric field dependence of the permittivity of ferroelectric thin films can be described. It is further shown that both reversible and irreversible components of the permittivity decrease linearly with the logarithm of…
Macrostrain variations in engineering components are frequently examined using neutron diffraction, at both reactors and pulsed sources. It is desirable to minimize the sampling volume in order to maximize the spatial resolution, although this increases the required measurement time. At reactors, macrostrain behavior…
It is shown that at weak alternating stress the relationship between the piezoelectrically induced charge and applied stress in ferroelectric ceramics has the same form as the Rayleigh law for magnetization versus magnetic field in ferromagnetic materials. Applicability of the Rayleigh law to the piezoelectric effect…
The piezoelectric properties of relaxor based ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 were investigated for electromechanical actuators. In contrast to polycrystalline materials such as Pb(Zr,Ti)O3, morphotropic phase boundary compositions were not essential for high…
Both off-Bragg and Bragg blazing phenomena, observed in a periodic strip grating over a grounded dielectric, are described, along with some discussion of the differences of the blazing phenomena in this geometry in comparison with those of the previous rectangular groove geometry.
Quantum well infrared photodetectors do not respond to normal incident light due to the quantum mechanical selection rules associated with intersubband transitions. Thus alternate light coupling systems, such as gratings are required in order to deflect the incoming light away from the normal. The resolution of the ph…
The one-step model of valence-band photoemission and inverse photoemission from single-crystal surfaces is reformulated for generalized (non-local, complex and energy-dependent) potentials. Thereby, it becomes possible to account for self-energy corrections taken from many-body electronic-structure calculations. The o…
We present a novel method for the calculation of the static and electronic dielectric tensor of polar insulating crystals based on concepts from the modern theory of dielectric polarization. As an application, we present the first ab initio calculation of the dielectric constants in the wurtzite III-V nitrides AlN, Ga…
The ${}^{27}$Al and ${}^{63}$Cu spin-lattice relaxation rates were found to contain a large ${T}^{2}$ term over a wide temperature range below 400 K in several thermodynamically stable quasicrystalline alloys, including $i$-AlCuRu, $i$-AlPdRe, $i$-AlCuFe, and the crystalline approximant phase \ensuremath{\alpha}-AlMnS…
Numerically minimizing a continuous free-energy functional which yields several modulated phases, we obtain the order-parameter profiles and interfacial free energies of symmetric and nonsymmetric tilt boundaries within the lamellar phase, and of interfaces between coexisting lamellar, hexagonal, and disordered phases…
Entropically stabilized quasicrystals are usually modeled as equilibrium ensembles of random tilings. In several models, such as the two-dimensional square-triangle tiling studied here, the corresponding kinetics may be very slow because a large number of tiles must be rearranged at each step through the ensemble. Her…
Nickel oxide, , thin films were studied by means of x-ray absorption spectroscopy at the Ni K edge. Thin films were prepared by reactive dc magnetron sputtering of a nickel target in an atmosphere that was an Ar - mixture. The results of the EXAFS analysis show that the thin films have nanocrystalline structure, which…
The ferromagnetic compound La3−3xCa1+3xMn3O10 with a triple perovskite structure can be successfully synthesized by using a thin-film growth method. Sputtered a-axis thin films with x=0.3 have been examined with respect to their magnetotransport properties. For the triple perovskite compound, we have observed the feat…
We present a novel, general, semiclassical theory of electron transport in a carbon nanotube exposed to an external electric field. The charge carriers are treated in the framework of the simplified tight-binding model. Simultaneous exposure to rapidly oscillating (ac) and constant (dc) electric fields is considered t…
Photostimulated luminescence phenomenon was observed in a fluoroaluminate glass doped with Eu2+. When the x-ray irradiated glass was excited by a He–Ne laser (633 nm), photostimulated luminescence at 400 nm due to the 5d–4f transition of Eu2+ ions was observed. X-ray absorption spectra showed that a part of Eu2+ conve…
The elastic response of aqueous foam to oscillating shear strain is probed by diffusing-wave spectroscopy. At low strains, the local bubble displacements are shown to be compatible with linear elastic behavior. At higher strains, a crossover to nonlinear but still fully periodic displacements is observed. To explain t…
We consider the behavior of an Ising ferromagnet obeying the Glauber dynamics under the influence of a fast switching, random external field. Analytic results for the stationary state are presented in mean-field approximation, exhibiting a novel type of first order phase transition related to dynamic freezing. Monte C…
The Ultra Quantum Crystal phases observed in quasi-one-dimensional conductors of the Bechgaard salts family under magnetic field exhibit both Spin Density Wave order and a Quantized Hall Effect. As a result, they also possess a Magneto-Roton mode within the single particle gap, and the usual Goldstone modes. The sign…