Materials Literature
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▪ Abstract This paper reviews the literature on size effects in ferroelectric materials, with an emphasis on thin film perovskite ferroelectrics. The roles of boundary conditions, defect chemistry, electrode interfaces, surface layers, and microstructure in controlling the measured properties of ferroelectric films, a…
▪ Abstract The formation of switchable holographic gratings from polymer-dispersed liquid crystals (H-PDLCs) allows for the development of switchable transmissive and reflective diffractive optics. These structures are created by the coherent interference of laser radiation within a syrup containing photoreactive mono…
Ultrafine fibers of polyaniline doped with camphorsulfonic acid (PAn.HCSA) blended with polyethylene oxide (PEO) were prepared by a non-mechanical, electrostatic spinning (“electrospinning”) technique. The morphology and fiber diameter of electrospun polyaniline blend fibers revealed that both the PEO and the PAn.HCSA…
Contour plots of disorder reaction energies across a wide variety of A 2 B 2 O 7 pyrochlore oxides have been produced, using atomistic simulation calculations based on energy‐minimization techniques. The cations studied range from Lu 3+ to La 3+ on the A site and from Ti 4+ to Ce 4+ on the B site. The present results…
A general equation for the susceptibility of disordered systems is proposed. It is based on the experimental observation of power laws at frequencies far from the peak frequency of the imaginary part of the frequency dependent relaxation function, the susceptibility. The obtained general expression contains the equati…
▪ Abstract We review the rapid progress made in our understanding of the crystal properties of semiconductors and nanocrystals focussing on theoretical results obtained within the multiband effective mass approximation. A comparison with experiment shows these results are valid for nanocrystals down 22–26 Å in diamete…
A simple procedure has been developed for the syntheses of functionalized mesoporous materials with sulfonic groups involving the co-condensation of tetraethoxysilane and mercaptopropyltrimethoxysilane in the presence of block copolymers and hydrogen peroxide under acidic conditions. The modified SBA-15 materials show…
▪ Abstract In the last decade of the twentieth century there has been a significant increase in research on a more than 100-year old phenomenon—the magnetocaloric effect (MCE). As a result, many new materials with large MCEs (and many with lesser values) have been discovered, and a much better understanding of this ma…
A likelihood-based approach to density modification is developed that can be applied to a wide variety of cases where some information about the electron density at various points in the unit cell is available. The key to the approach consists of developing likelihood functions that represent the probability that a pa…
▪ Abstract Solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤5%, are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properti…
We propose new schemes of high-resolution coherent four-photon spectroscopy where chirped pulses are employed for the Raman excitation of a nonlinear medium. The use of linearly chirped pulses in coherent anti-Stokes Raman scattering spectroscopy allows the spectra of nonlinear susceptibility to be studied with a tera…
Orthorhombic epitaxial Sr2CeO4 thin-film phosphors were grown on (100) SrTiO3 and yttria-stabilized-zirconia (YSZ) single crystal substrates with epitaxial relationships of (100) [010]Sr2CeO4//(100)[010]SrTiO3 and (100)[010]Sr2CeO4//(100)[011]YSZ, respectively. As-deposited films exhibit a broadband photoluminescence…
Blueshift of the band gap due to quantum confinement is calculated in a tight-binding model for a series of nine III–V zinc-blende AB (A=Al, Ga, or In, B=As, P, or Sb) and two diamond group-IV (Si and Ge) semiconductor clusters. Analytic expressions for the highest occupied molecular orbital and lowest unoccupied mole…
We report here a light-induced phenomenon—a self-induced rotation of the azimuth of elliptically polarized light passing through photobirefringent azopolymers. The experiments are carried out with films of amorphous and liquid-crystalline polymers. It has been shown that the induced rotation angle depends on the ellip…
Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 grown by the pulsed laser deposition technique were found to possess superior perfor…
Green upconversion emissions at 548 and 528 nm have been obtained from sol-gel derived nanocrystalline Er3+:BaTiO3 films under 980 nm excitation. The green emissions are attributed to the ground-state (4I15/2) -directed transitions from H11/22 (528 nm) and S3/22 (548 nm) of Er3+ ions. Analysis of the temporal evolutio…
A series of bulk polycrystalline La1−xAgxMnO3 samples with x ranging nominally from 0 to 0.5 were prepared by conventional solid-state reaction processing in air. X-ray diffraction patterns show that the samples contain a single perovskite phase when x⩽0.25, and are composed of two phases (a magnetic perovskite phase…
The structure of filamentous carbon formed upon catalytic decomposition of hydrocarbons on iron subgroup metals and their alloys is considered. The regularities of the deposition of carbon on these metals are generalised. The carbide cycle mechanism of carbon formation is considered in detail. The growth models of som…
Thick films of aligned single wall carbon nanotubes and ropes have been produced by filtration/deposition from suspension in strong magnetic fields. We measured mosaic distributions of rope orientations in the film plane, for samples of different thicknesses. For an ∼1 μm film the full width at half maximum (FWHM) der…
Point defects (vacancies, solute atoms, and disorder) are ubiquitous in crystalline solids. With in situ transmission electron microscopy we find clear evidence for the existence of a universal symmetry property of point defects; i.e., the symmetry of short-range order of point defects follows the crystal symmetry whe…