Thermodynamics of single-domain BaTiO3 and PbTiO3 epitaxial thin films

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Pyrochlore free 0.9Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) thin films were prepared from alkoxide-based solution precursors. Preferential (111) crystallographic orientation was obtained on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating. Dielectric, electrostrictive, and piezoelectric properties of the films were characterized in detail. Films show relaxor-like behavior, but with dielectric permittivity which is low (around 4300 at peak and at 340 Hz with E-ac=1.6x10(6) V/m) compared to bulk ceramics and single cryst

We report on x-ray photoemission and absorption measurements on ruthocuprate and SrRuO3 samples. The ruthocuprates include samples that are both weak ferromagnets and superconductors for part of the phase diagram. The results indicate that adding hydrogen changes the many-body response on the CuO2 planes. The results further indicate that ferromagnetic order alters the core level states. We discuss implications of these data.

The paper discusses different possibilities for controlling piezoelectric properties of ferroelectric materials and devices. The piezoelectric properties engineering can be made on different scales. Tuning of the piezoelectric response by controlling contributions from domain walls displacement is used to illustrate engineering on nanometer scale. Texture control in ferroelectric films and grain size control is discussed as an example of property control on micrometer scale. Finally, engineering on macrosco

The low-pressure phase diagram of solid poly(tetrafluoroethylene) (PTFE/Teflon) has been investigated using const.-temp./const.-pressure mol.-dynamics techniques and a new all-atom potential model for fluorocarbons. The simulation was started in an ordered low-temp. phase in which the mols. are parallel and have a helical conformation with a pitch of uniform magnitude and sign (chirality). In accordance with expt., a transition to an orientationally disordered state is obsd. upon heating. The coherent helic

The high- and low-temperature forms, i.e., phase I (stable above 328 K) and phase II (stable below 328 K), of Cu8GeSe6 have been investigated by the powder X-ray diffraction method. Cu8GeSe6 II is hexagonal with A = 12.6438(2), C = 11.7570(1) Angstrom, Z = 6, and P6(3)cm, and its structure is considered to be a superstructure of the high-temperature form, Cu8GeSe6I (hexagonal, a = 7.3164(4) congruent to A/root 3, c = 11.7679(7) Angstrom, Z = 2, and P6(3)mc). Rietveld analysis of Cu8GeSe6 I (350 K) and II (2

Piezoelectric coatings of PbZrxTi1-xO3 (PZT) were deposited on standard telecommunication fibers. The PZT coatings were produced by reactive de magnetron sputtering of metal targets in pure oxygen atmosphere. The deposition was carried out at substrate temperatures between 500 and 600 degrees C. Film thicknesses are in the range of 1300 to 1500 nm. The device structure under investigation is of the Ti/Pt/PZT/Au type. X-ray diffraction (XRD) scanning electron microscopy (SEM), and electrical measurements wer

Gas phase methylation of catechol by methanol over modified gamma-alumina catalysts is studied experimentally. The catalyst composition and the reaction conditions are optimized to attain the highest selectivity towards 3-methylcatechol (C-methylation) or guaiacol (O-methylation and to diminish the catalyst deactivation. The modified gamma-alumina {Li+ 3 % Mg2+ 5 %/gamma-Al2O3} was found to be the best with respect to the 3-methylcatechol formation. At 350 degrees C and at a conversion level of 28% the sele

The authors describe a two-dimensional high-resoln. solid-state NMR methodol. for correlating the dynamics of mol. rearrangements around the crit. points of equil. phase transitions in mol. solids. It combines the techniques of temp.-jump and two-dimensional (2D) NMR spectroscopy. The two spectral dimensions are the isotropic chem. shifts at different sample temps. The technique is illustrated by elucidating the dynamic rearrangement of the C4O4 units of squaric acid (H2C4O4) in relation to the mechanism of

Piezoelectric coefficients and electric field-induced strains are investigated in Ca-modified PbTiO3 (PCT) films deposited by sol-gel technique. The microstructural evolution and related electromechanical properties are studied as a function of Ca content and porosity of the films. The porosity is tailored by changing the heating rate during the final crystallization anneal. It is found that piezoelectric properties of porous films heated at slow rates are superior to those of dense films crystallized using

X-ray microanalysis have been made on a suite of nine oilwell cement clinkers. Elemental data were obtained on alite, belite, and ferrite phases and, for two clinkers only, also on aluminate. The alite and belite compositions are broadly similar to those previously reported for other portland cements. Guest ion concentrations suggest that several charge-balancing substitutions occur. bulk MgO and SO3 levels determine the Mg and S contents of both phases, but for Fe and Al the substitution levels are not str

We report transport measurements on single crystals of Sr2RuO4-δ, grown by the flux technique. The temperature dependence of the Hall coefficient is similar to the one measured in cuprates, and the linear resistivity persists up to ~1000 K, while the superconductivity remains confined below 1 K. This suggests that the linear temperature dependence of resistivity is not an exclusive signature of the anomalous normal state of high-Tc cuprates but rather of layered oxides in general, especially single-layer pe

The laser flash photolysis of I was studied over a wide pressure range in several bath gases. At low pressures the obsd. quantum yield for photolysis at 6943 .ANG. is independent of the gas d., whereas at higher pressures the quantum yield decreases with increasing gas d. This phenomenon is discussed in terms of the cage effect, and the measured yields are compared with model calcns. The expts. also provide information on the second order rate consts. for I atom combination.

Thermodynamics of single-domain BaTiO3 and PbTiO3 epitaxial thin films

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Dielectric and electromechanical properties of ferroelectric-relaxor 0.9 Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) thin films

Photoabsorption and core-level photoemission study of ruthocuprates

Engineering of piezoelectric properties in ferroelectric ceramics and thin films

Conformational and orientational order and disorder in solid polytetrafluoroethylene

Superspace-group approach to the phase transition of Cu8GeSe6

PZT coated optical fibers for acousto-optical modulation

Selective C-and O-methylation of catechol in gas phase over modified g-alumina

Temperature-Jump 2D NMR Spectroscopy in Crystalline Solids: A Technique for Correlating Molecular Reorientation across the Phase Boundaries of an Order-Disorder Lattice

Electromechanical properties of sol-gel derived Ca-modified PbTiO3 films

Oilwell cement clinkers x-ray microanalysis and phase composition

On linear resistivity from ~1 to 103 K in Sr2RuO4-δ single crystals grown by flux technique

The photolytic cage effect of iodine in the gas phase