111Cd-TDPAC study of pressure effect on the valence of Yb in the YbGe2.85 cubic phase

Crystal structure of [Formula: see text] compound was studied using Atomistix Tool Kit software program at high pressure. It is defined that in this combination, tetragonal–cubic phase transition occurs under high pressure [Formula: see text] GPa. The character of this phase transition is explained in respect of baric dependence of spontaneous strain. Birch–Murnaghan equation is solved, compression ratio is determined. Results gained by theoretical calculations are compared with experimental values.

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Use of fractals to describe microstructures of porous thick-film platinum electrodes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121971 ◽

1992 ◽

Vol 50 (1) ◽

pp. 314-315

Author(s):

Steven D. Toteda

Keyword(s):

Fractal Dimension ◽

Power Plants ◽

Electrical Response ◽

Cubic Phase ◽

Platinum Electrodes ◽

Fine Grained ◽

Impedance Response ◽

Platinum Particles ◽

Energy Surfaces ◽

Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

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Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150253 ◽

1993 ◽

Vol 51 ◽

pp. 884-885

Author(s):

David M. Anderson ◽

Tomas Landh

Keyword(s):

Liquid Crystalline ◽

Diblock Copolymers ◽

Cubic Phase ◽

List Type ◽

Interpenetrating Networks ◽

Triply Periodic ◽

Wide Range ◽

Bicontinuous Cubic ◽

Phase Liquid ◽

Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

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Ferroelectric Domain Structure of Pb(Zr.52Ti.48)03

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600000933 ◽

1980 ◽

Vol 38 ◽

pp. 214-215

Author(s):

E.K. Goo ◽

R.K. Mishra

Keyword(s):

Phase Transformation ◽

Domain Structure ◽

Tetragonal Phase ◽

Ferroelectric Domain ◽

Cubic Phase ◽

Ion Milling ◽

Thin Foils ◽

Ferroelectric Domain Structure ◽

Ferroelectric Domains

Ferroelectric domains are twins that are formed when PZT undergoes a phase transformation from a non-ferroelectric cubic phase to a ferroelectric tetragonal phase upon cooling below ∼375°C.,1 The tetragonal phase is spontaneously polarized in the direction of c-axis, making each twin a ferroelectric domain. Thin foils of polycrystalline Pb (Zr.52Ti.48)03 were made by ion milling and observed in the Philips EM301 with a double tilt stage.

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