Materials Literature
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A series of sintered composite materials was fabricated from Parascan™ barium strontium titanate (BSTO) and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied from zero (BSTO only) to 100wt% (ferrite only). X-ray diffraction data show the presence of a third, nonmagnetic phase that sets the ferrite…
The phase transitions of Ge2Sb2Te5 (GST) films after bombardment with 40keV N2+ ions were investigated. Comparing the nitrogen incorporated GST films with a pure GST film, the suppression of a crystalline grain growth was more effective in the N2+ implanted GST film than in a nitrogen codeposited GST film, i.e., x-ray…
Bismuth-doped LaAlO3 was prepared in the form of solid solution, La(1−x)BixAlO3 (0⩽x⩽0.2), by solid-state reactions. The materials were characterized by x-ray diffraction and dielectric spectroscopy. With increasing bismuth amount (x), the dielectric constant increases from 31.6 for pure LaAlO3 to 34.6 for x=0.2, whil…
The polycrystalline nanosize (∼60nm) of (1−x)Pb(Fe2∕3W1∕3)O3–x(BiFeO3) solid solutions with a wide range of concentrations (0⩽x⩽0.20) were fabricated using a mechanical activation followed by a conventional solid-state reaction technique. The formation of single-phase material and better solubility of two phases [i.e.…
We present a theoretical study on the structural and electronic modifications caused by random nitrogen substitution in carbon tubular and branched nanostructures. Finite cluster calculations with hydrogen saturation of the tube ends were performed. Geometry optimizations were carried out through semiempirical quantum…
The essential first step in semi-solid forming is to obtain a high grain density during the initial stages of solidification of an alloy melt. This is usually done by a combination of cooling and convection. If the grain density is too low, the resulting structure is one of conventional coarse dendrites, unsuitable fo…
The size effect in barium titanate (BaTiO3) was investigated both experimentally and theoretically. Tetragonal BaTiO3 powders with average sizes from 80to420nm were directly prepared by different hydrothermal methods. The tetragonality of the hydrothermal BaTiO3 decreased with decreasing particle size, which exhibited…
A field summation method is used to determine the effective ε and μ of metamaterial structures. The numerical implementation of this method using commercial software is comprehensively described. The field summation method is shown to predict accurately the reflection and transmission coefficients of thin slabs of met…
Minority electron diffusion length was measured in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. A thermally induced increase of electron diffusion length was determined to have an activation energy of 184±10meV. Irradiation with a low energy (5kV) electron beam a…
This paper compiles all the data from our tracer diffusivity studies in single crystalline 2/1-mullite. As tracers we used the rare stable isotopes 18O and 30Si and the artificial pseudo-stable isotope 26Al. Secondary-ion mass spectrometry was applied to analyze the depth distribution of the tracer isotopes after the…
We calculate the band structures of BaO and BaS using the local density approximation and the GW approximation (GWA). The Ba 4d states are treated as valence states. We find that BaO is an indirect band-gap semiconductor and BaS is a direct band-gap semiconductor. The results show that the band gaps of GWA agree excel…
We calculated size-dependent single particle energy eigenvalues, wave functions, energy band gap, and dielectric constant for a semiconductor nanocrystallite, within the framework of the two band Penn model. The finite size effects are presented as size-dependent correction terms to the energy eigenvalues and the ener…
Cs Br : Eu 2 + has recently been investigated as a photostimulable x-ray storage phosphor with great potential for application in high-resolution image plates. In a recent paper Hackenschmied et al. [J. Appl. Phys. 93, 5109 (2003)] suggested that segregations of CsEuBr3 or Cs4EuBr6 formed within CsBr:Eu2+ during annea…
The electronic structure and optical properties of the rare earth sesquioxides (R2O3, R=La, Pr, and Nd) have been studied using the full potential linearized augmented plane wave method within local spin density approximation (LSDA) and Coulomb corrected local density approximation (LSDA+U) as implemented in the WIEN2…
The magnetocaloric effect of the FeCrMoCuGaPCB alloy series, suitable for being prepared as bulk amorphous alloys, has been studied. Optimal refrigeration cycles have a cold reservoir close to room temperature. The refrigerant capacity of these alloys is comparable to that of a Mo-containing Finemet-type alloy and is…
Porous silicon rugate filters are fabricated and investigated for their ability to sense chemical species. The durability of the filter is tested by allowing the structure to undergo many cycles of adsorption and desorption of vapor-phase ethanol molecules. The characteristic reflectivity peak of the structure exhibit…
The direct piezoelectric response d33 of [001]C-poled 0.955Pb(Zn1∕3Nb2∕3)O3–0.045PbTiO3 [PZN-4.5PT] and 0.98Pb(Zn1∕3Nb2∕3)O3–0.08PbTiO3 [PZN-8PT] has been investigated as a function of temperature upon heating above 40°C to the paraelectric phase. Using a Rayleigh-law based analysis, it is shown that both the reversib…
Optoelectronic measurements of carbon nanotube transistors have shown a wide variety of sensitivites to the incident light. Direct photocurrent processes compete with a number of extrinsic mechanisms. Here we show that visible light absorption in the silicon substrate generates a photovoltage that can electrically gat…
Indium-tin-oxide (ITO) thin films on polyethylene napthalate (PEN) with high carrier concentration (∼1021∕cm3) have been grown by electron-beam deposition without the introduction of oxygen into the chamber. The electrical properties of the ITO films (such as, carrier concentration, electrical mobility, and resistivit…
The modification of acoustic phonons in semiconductor nanostructures embedded in a host crystal is investigated including corrections due to strain within continuum elasticity theory. Effective elastic constants are calculated employing {\em ab initio} density functional theory. For a spherical InAs quantum dot embedd…