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Showing 1 to 17 of 17 for “"Nonstoichiometry"”.
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Nonstoichiometry of chalcocite in water-xanthate systems
E<sub>h</sub>-pH diagrams were constructed from mass-balanced, computer calculations for the copper-sulfur-water system involving different Cu/S ratios that pertain to chalcocite, djurleite, anilite and covellite. Calculations were completed for cases where oxidation of the sulfur proceeded to i) …
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Synthesis, electrical conductivity and nonstoichiometry of dopped layered perovskites
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1999.
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Effect of nonstoichiometry on the magnetism and ferroelectricity of Fe- and Co-substituted strontium titanate thin films
Multiferroic and magnetoelectric materials, in which the magnetic properties can be controlled via electric field and vice versa, hold the potential to be useful in several emerging memory technologies, including spin-wave devices and multi-state memory. Room temperature ferromagnetism and …
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Materials and devices for optical switching and modulation of photonic integrated circuits
… Fundamental material transport properties and nonstoichiometry in VO2 were characterized. Nonstoichiometry as high as 5% was measured. A Frenkel defect model was used to describe the behavior in V02 in which vanadium interstitials were attributed to be the dominant ionic defect in the reducing …
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Strukturelle und elektronische Untersuchungen am hoch sauerstoffdefizitären Mischleiter Ba x Sr 1-x Co 0,8 Fe 0,2 O 3-delta (BSCF)
… out as it accommodates an extremely high oxygen nonstoichiometry delta which leads to one of the highest oxygen permeation rate know thus far. This makes BSCF a promising candidate for industrial application as material for oxygen separation membranes. Unfortunately, BSCF tends to decompose into …
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Investigation on the phase stability and defect structure of Li-Mn-O and Li-Me-Mn-O spinel (Me=Mg, Ni, Co)
… and (Li, Me, Mn)3O4–delta is determined. The nonstoichiometry change was measured by TG as function of pO2 variation, and Deltadelta–pO2 diagram was fitted by using different defect models. It is concluded that in a lithium excess spinel, the excess Li ions substitute for Mn ions on octahedral …
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Oxygen transport in Ba(Fe,Co,Zr)O 3 - delta membranes
The nonstoichiometry of Ba(Fe,Co,Zr)O3-delta (Zr-lean Ba(Fe,Co,Zr)O3-delta) is measured as a function of temperature and oxygen activity by TG. Very high nonstoichiometry (delta0=0.78 at a(O2)=1) is determined at 1273 K. From the nonstoichiometry of Ba(Fe,Co,Zr)O3-delta;, exponent n (n=-0.01) in …
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Oxidation kinetics of polycrystalline SrTiO₃ and LaCrO₃
… concentration due to the native oxygen excess nonstoichiometry of the oxide with its higher hole mobility results in p-type conduction. The experimental results also indicate that the electron mobility in this material is about 0.002 cm<sup>2</sup>/V-sec at 1200 °C""--Abstract, p. ii</p>
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Characterization and control of non-stoichiometry in Pr₀.₁Ce₀.₉O₂-[d̳e̳l̳t̳a̳] thin films : correlation with SOFC electrode performance
… oxide thin films often depend strongly on oxygen nonstoichiometry (6), there have been few means available for its measurement and control in a reliable and in-situ fashion. In this work, we investigate means for extracting the oxygen nonstoichiometry of dense oxide thin films as a function of …
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Nanostruktūrizuotų manganitų sluoksnių, legiruotų kobaltu, auginimas ir tyrimas /
… for thin LSMCO films exhibiting manganese nonstoichiometry and difference in cobalt content ranging from 0 to 0.17. LSMCO films grown on LaAlO3 substrates were epitaxial, while nanostructured films formed on sapphire-R and Al2O3 substrates. Structural studies have revealed that epitaxial …
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Electro-chemo-mechanical Studies of Perovskite-Structured Mixed Ionic-Electronic Conducting SrSni-₁₋xFexO₃₋x/₂₊[epsilon]
… structure and higher electron mobility. Oxygen nonstoichiometry and the defect chemistry of the SrSni-₁₋xFexO₃₋x/₂₊[epsilon] (SSF) system were examined by means of thermogravimetry as a function of oxygen partial pressure in the temperature range of 973-1273 K. Marginally higher reducibility was …
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Chemomechanics of non-stoichiometric oxide films for energy conversion
… induced high temperature actuation and nonstoichiometry- dependent mechanical properties that are modulated by environmental conditions including temperature and oxygen partial pressure. We then explore the mechanisms and microstructural contributions to these effects via computational …
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Defect chemistry, transport properties and thermodynamic stability of acceptor doped and undeoped layered La 2 NiO 4
… Wagner theory in conjunction with data of oxygen nonstoichiometry and diffusion coefficients from literature. Defect modeling reveals that with decreasing p(O2) on the oxygen-lean side, the vacancy concentration in the membrane increases and the contribution of vacancy transport becomes more and …
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Defects and Ionic Transport at Reduced Temperatures -- Electric Field and Optical Control on Nanoscopic Spatial Scales
… in ionic mobility with increases in oxygen nonstoichiometry from 0.032 ± 0.001 to 0.042± 0.001 was observed at 60°C. We discuss how nonobvious entropic effects can lead to these ionic mobility – defect concentration trends, contrary to expectations and how being able to control and quantify …
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Sintering kinetics and properties of highly pure lead zirconate titanate ceramics
… The impact of starting materials, lead nonstoichiometry, and dopants was examined. The sintering behavior was monitored in a thermo-optical dilatometer and a kinetic-field approach was employed to obtain the activation energy for sintering of PZT ceramics with different compositions. The …
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Phase formation and structural transformation of strontium ferrite SrFeOx
Non-stoichiometric strontium iron oxide is described by an abbreviated formula SrFeOx (2.5 ≤ x ≤ 3.0) exhibits a variety of interesting physical and chemical properties over a broad range of temperatures and in different gaseous environments. The oxide contains a mixture of iron in the trivalent …
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Phase formation and structural transformation of strontium ferrite SrFeOx
Non-stoichiometric strontium iron oxide is described by an abbreviated formula SrFeOx (2.5 ≤ x ≤ 3.0) exhibits a variety of interesting physical and chemical properties over a broad range of temperatures and in different gaseous environments. The oxide contains a mixture of iron in the trivalent …