Materials Literature
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We study the electronic structure of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3+\mathrm{\ensuremath{\delta}}}$, x=0, 0.1, 0.2, 0.3, and 0.4, across the semiconductor-metal transition, using various electron spectroscopy techniques. The negligible intensity seen a…
We discuss the formation of gold metal colloids in a variety of surfactant/solvent systems. Static and dynamic light scattering, small angle x-ray and neutron scattering, TEM analysis, and UV-visible absorbance are used to characterize the kinetics of formation and final colloid stability. These gold colloids exhibit…
The structure and the electronic properties of graphite monofluoride (CF${)}_{\mathit{n}}$ have been studied within the framework of the density-functional technique, using nonlocal ionic pseudopotentials and a large number of plane waves. The chair conformation is shown to be energetically favored with respect to the…
The Ωt intensity parameters (t=2,4,6) of Er3+ ions in several oxide glasses and the isomer shift (IS) of 151Eu Mössbauer spectra in glasses of the same composition were determined. Among these Ωt’s, the Ω6 parameter was found to have a good relation with IS; Ω6 decreases with an increase of IS which reflects the 6s el…
We present soft-x-ray-absorption spectra (XAS) of ${\mathrm{LaCoO}}_{3}$ taken at different temperatures (80--630 K). The shape of the multiplets in the Co 2p XAS spectra conveys information on the symmetry and spin of the ground state. The O 1s XAS spectra are related to unoccupied metal bands through covalent mixing…
The occurrence of metastable or stable domain states on mesoscopic length scales seems to be a widespread property of many solids undergoing phase transitions in the presence of quenched random fields. A survey is given on the experimental evidence of domain states in various magnetic, ferroelectric and structural sys…
We investigate the effect on the thermoelectric figure of merit of preparing materials in the form of one-dimensional conductors or quantum wires. Our calculations show that this approach has the potential to achieve a significant increase in the figure of merit over both the bulk value and the calculated superlattice…
Silicon carbide (SiC) thin films were deposited on titanium carbide (TiC) substrates by pyrolysis of 1,3 disilacyclobutane (C2H8Si2), at atmospheric pressure, in an inverted-vertical cold-wall chemical vapor deposition reactor. The growth rate, morphology, and crystallinity of the films were studied, at constant C2H8S…
This review surveys the behaviour of graphite under loading conditions in which the stressing is on the whole tensile. The performance of a recently introduced model of graphite failure is reviewed in relation to the models from which it was developed, and against data obtained from a wide range of experiments on the…
A new noncontact calorimetric method has been developed based on inductive heating of a metallic spherical bulk sample by a power-modulated radio-frequency field under ultrahigh vacuum conditions. From the pyrometrically measured temperature response the specimen’s external (due to radiative heat loss) and internal re…
The initial permeability of soft polycrystalline ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature T c to below. The temperature loops are classified into two categories according to the presence or absence of a secondary peak (SP), in addition to the Hopkinson peak,…
A model pair potential is calculated for Mn-Mn pairs in Al using a Green's function method. The pair potential has a preferred spacing of 4.7 \AA{}. The energy resulting from these Mn-Mn interactions strongly favors the ${\mathrm{Al}}_{6}$Mn, \ensuremath{\alpha}-AlMnSi, and icosahedral quasicrystal structures relative…
A striking evolution of the I-V curves is observed in a single sample (i.e., for a given realization of quenched disorder) of the charge density wave conductor ${\mathrm{NbSe}}_{3}$ in the presence of an external rf field of varying amplitude. This yields qualitatively different ``depinning transitions'' from the pinn…
The observation of photoluminescence (PL) spectral shifts during anodization of porous Si and after immersion in different chemical solutions is reported. These shifts in the PL spectra are attributed to changes in the surface chemistry achieved by changing the composition of the electrolyte in which the samples are i…
Synthetic amphiboles of the richterite―Ti-richterite series have been examined by synchrotron X-ray absorption spectroscopy to determine the oxidation state and coordination of Ti in their structure. The Ti K-edge in the amphiboles is displaced to energy values higher than that of Ti metal (4966.0 eV) and consists of…
The abundance of the structural units in alkali silicate melts, supercooled liquids, and glasses determined in-situ from 25 to 1651°C has been used to estimate the enthalpy (ΔH) for the disproportionation reaction, Si 2 O 5 (2Q 3 ) ↔ SiO 3 (Q 2 ) + SiO 2 (Q 4 ). The enthalpies are in the range of -34 to 30 kJ/mol with…
Synchrotron radiation photoemission spectroscopy suggests that the room temperature grown Au/Si(111) interface is an abrupt interface with the contact made by metallic Au and bulk Si. Si 2p core level spectra show no sign of an interface component, but only the surface reacted and bulk Si components during the growth…
In the present review on the rod-based sulphosalt structures we describe the fundamental features of their large- to medium-scale crystal chemistry. The principal, lozenge-shaped rods in these structures represent portions based on the SnS or PbS archetype, with their surfaces being alternatively of the pseudotetragon…
A modification of an earlier technique, to measure the distribution of space charge in the insulation of a coaxial cable, under both DC and AC electric fields, is described. The mathematical analysis is developed on the basis of acoustic waves propagating in media with cylindrical geometry. In order to measure the cha…
Raman spectra of diamond powders with size less than 2 μm have been measured as a function of the particle size. The Raman line was found to become more asymmetric with some tailing towards lower Raman shifts, broader, and weaker with decreasing particle size. The observed result can be explained by a phonon confineme…