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Non-stoichiometric nickel oxide was synthesized by the thermal decomposition method at different sintering temperatures upto 1100 °C. The samples were analyzed by thermogravimetric analysis (TGA). Wherein, the stoichiometry of the sample was analyzed by calculating the excess oxygen. It was found that as the sintering temperature of the precursor increases the excess oxygen present in the sample decreases, and at temperature above 700 °C, the sample becomes stoichiometric. These results were interpreted as the decomposition temperature increases, which heals the defects present in the non-stoichiometric nickel oxide. Thus, highly defective nickel oxide at lower decomposition temperature approaches stoichiometric nickel oxide as the temperature is increases above 700 °C.

We have successfully synthesized polycrystalline bulk samples of La 2 CuO 4 with the Nd 2 CuO 4 -type (T′) structure at low temperatures. First of all, La 2 CuO 4 with the K 2 NiF 4 -type (T) structure was prepared by the conventional solid-state reaction. Secondly, La 2 CuO 3.5+ δ with the Sr 2 CuO 3 -type structure was obtained by heating mixed powder of T-La 2 CuO 4 and CaH 2 at 175 °C in an evacuated Pyrex tube. Thirdly, T′-La 2 CuO 4+ δ was prepared by heating La 2 CuO 3.5+ δ at 250 °C in air. Finally, T′-La 2 CuO 4+ δ was reduced using CaH 2 to remove excess oxygen. The powder X-ray diffraction pattern has revealed that the product is of the single phase of T′-La 2 CuO 4 , but no superconductivity has been observed at T > 2 K in the magnetic susceptibility measurement. The residual excess oxygen may suppress the appearance of superconductivity.

In this paper, standard genetic algorithms (SGAs) are presented to optimise the decentralised discrete PID parameters by three tuning approaches for a multivariable glass furnace with single loop interaction. At initial state, with the aid of control oriented model, the individual tuning approach without loop interaction is considered to categorise the genetic operators, personalised cost functions and improved searching boundaries to attain the performance criterions. The second tuning approach is considered in PID parameters optimisation with loop interaction with optimum cost function. While, the third tuning approach is considered by modifying the optimum cost function by including the total effect of glass temperature and excess oxygen of both variables. The modified cost function exhibits better control robustness and disturbance rejection under loop-interaction.

In this paper, the potential of standard genetic algorithms (SGAs) are presented to optimise the discrete PID parameters for multivariable glass furnace. Control oriented models of each multivariable glass furnace; glass temperature and excess oxygen are used to optimise the discrete controller with personalised cost function and adjusted boundaries by SGAs, individually. Well optimised discrete PID parameters by control oriented model are applied to realistic multivariable model by decentralised method.

The crystallization process from a solution begins with nucleation, which determines the structure and size of the resulting crystals. Further understanding of multi-pathway crystallizations from solution through two-step nucleation mechanisms is needed. This study uses density functional theory to probe the thermodynamic properties of alumina clusters at high temperature and reveals the thermodynamic relationship between these clusters and the saturation levels of dissolved oxygen and aluminum in an Fe–O–Al melt. Based on the thermodynamics of cluster formation and the experimental evidence for both excess oxygen in the Fe-O-Al melt and for alumina with a polycrystalline structure in solidified iron, we demonstrate that the appearance of various types of clusters that depends on the saturation ratio determines the nucleation steps that lead to the various crystallization pathways. Such mechanisms may also be important in nucleation and crystallization from solution.

Premature infants are vulnerable to the effects of early childbirth, which includes immature defenses against the early novel adaptation to oxygen. Developmental progress initiated early in the life cycle pushes the normal programming sequence in ways we only partially understand. In addition to antioxidant capabilities that are pushed possibly too soon, the exposure to excess oxygen is almost routine for the smaller younger infant. What role nutrition plays in the mosaic of prematurity is not certain, but we do know that what the infant is fed is clinically important perhaps more so than at any other time in the life cycle. Every attempt is made to introduce human milk as early as possible, the only food made by humans for humans. It is clear human milk can be tailored for the premature and perhaps for each and every infant. When the premature is too young for suckling, parenteral nutrition is needed which unexpectedly may increase the oxidative load of the premature infant. Technology while extending the life of many premature infants brings its own problems in need of resolution. The unfortunate creation of free radicals in solution while unintended and in fact only recently recognized creates iatrogenic issues. We describe nutritional advances in feeding the premature infant and the important role of nutrition as medicine has on outcome.

The green emission of lead tungstate (PbWO4) is closely related to structure defects. For studying the mechanism of the green emission, the local structure of PbWO4 has been first investigated by extended X-ray absorption fine structure using synchrotron radiation. The results indicate that the excess oxygen in air-annealed PbWO4 exists and forms "WO4 + O-i" centers. The green emission of PbWO4 is not caused by (WO3 + F) centers, but probably originates from the centers Of "WO4 + O-i". (C) 2001 Elsevier Science B.V. All rights reserved.

The effect of SO2 for the selective reduction of NO by C3H8 on Ag/Al2O3 was investigated in the presence of excess oxygen and water vapor. The NOx conversion decreased permanently even in the presence of a low concentration of SO2 (0.5–10 ppm) at

The recent developments on the effect of H2O on deNOx performance of a variety of SCR catalysts selectively removing NOx by hydrocarbons in excess oxygen have been reviewed. In particular, the water tolerance of the catalyst is summarized to illustrate a common deactivation behavior of SCR catalyst for the reduction of NO by hydrocarbons under wet feed gas mixture. Earlier proposals elucidating the possible cause of the catalyst deactivation under wet conditions are discussed, focusing mainly on the catalyst characteristics. A promising way, which can improve the water tolerance and the hydrothermal stability of zeolite-based SCR catalyst, is also described.

The presence of SO 2 had a considerable effect to increase the activity of Ir/SiO 2 catalyst for NO reduction with H 2 in the presence of excess oxygen, although NO reduction in the absence of SO 2 was completely unselective. Similar SO 2 promoting effect was also observed for NO reduction with CO or C 3 H 6 . Silica was found to be the best support for iridium.

The effects of oxygen doping (δ=0~0.19) and high pressure (P=0~5.07 GPa) on the electronic structure of HgBa2CuO4+δ have been studied by the recursion method. The hole concentration of the CuO2 layer increases monotonically as δ increases from 0 to 0.19. Each excess oxygen atom contributes about 1.9 holes to the CuO2 layer. The pressure-induced charge transfer, dn/dP, decreases for increasing δ, vanishing at over-doping level, which is consistent with the δ-dependence of dT c /dP observed in experiments.

Results of first-principles calculations on the structure and electronic structure of amorphous WO3 are presented. The effect of non-stoichiometry is investigated. In particular, we discuss the pairing of W5+ species in oxygen-deficient films resulting in deep in-gap states and its possible consequences for the electrochromic coloration efficiency. To this end, we make a connection with Raman experiments by calculating the vibrational density from molecular-dynamics simulation. For the W5+-W5+ stretch we find a low frequency mode at ~200 cm-1 which agrees well with the Raman data. We also estimate the stability of isolated W5+ species in stoichiometric and oxygen-deficient tungstentrioxide.

De-inking solid residue (DISR) doped with nitrates of 2000 mg/kg of Pb, Cd, and Cr was burned in supercritical water in a batch reactor. Combustion runs were carried out under supercritical water conditions: 30.6 MPa, 450 or 525°C, and 17.1% or 65.7% excess oxygen. The run time varied between 5 and 30 min. In all runs, more than 99.2% (up to 100%) of the Pb precipitated to ash, with leachability varying from 0.5% to 7.3% and decreasing with increasing run time and temperature. In runs at 450°C, the soluble Cd concentration showed little or no change, but its ash's leachability dropped when more oxygen was added. At 65.7% excess oxygen, when temperature was increased from 450 to 525°C, the Cd concentration and ash leachability declined, and a downward trend appeared with longer run time. In runs at 450°C and 17.1% excess oxygen, the soluble Cr concentration increased with time from 4.1% (5 min) to 19.2% (30 min). When 65.7% oxygen was applied, it declined to 12.6% at 30 min, which was followed by an increase from 15.0% (5 min) to 37.5% (15 min). In the runs with 65.7% oxygen, as the temperature went up from 450 to 525°C, the soluble Cr concentration rose to 26.1% at 5 min and subsequently showed a trend similar to that observed for the runs at 450°C. At 30.6 MPa, 525°C, and a 30-min run time, 100% of the Pb, 97.6% of the Cd, and 87.3% of the Cr were converted to an insoluble substance. Only 0.5% of the Pb, 0.6% of the Cd and 0.8% of the Cr in ash were leached. Tests with 20000 mg/kg Pb, Cd, and Cr were conducted under the same conditions (pressure/temperature/time). Only 0.03% of the Pb but 82.0% of the Cd and 79.4% of the Cr remained soluble. It was found that CO 2 and acetate from organics combustion could help to remove heavy metals via formation of insoluble carbonate salts. X-ray diffraction spectra indicated the presence of PbCrO 4 and Al 2 Si 2 O 5 (OH) 4 in the ash. Electron microprobe results showed a close connection between Pb and Cr but no relation between Pb and Cd in the ash. The main solid products were CdO, CdCO 3 , CrO 2 , HCrO 2 , PbCrO 4 , PbCO 3 and PbO x . In general, the combustion of DISR in supercritical water showed an effective removal of heavy metals.

The effect of partial Pb substitution for Bi on the oxygen stoichiometry and superconducting properties of Bi2Sr2CaCu2O8+δ was studied. The Pb content and heat-treatment conditions were optimized to attain the highest critical parameters. The observed changes in the superconducting properties were shown not to correlate with oxygen stoichiometry. Superconducting properties were found to persist in the absence of Cu in the formal oxidation state 3+. A reduction in the concentration of excess oxygen to about the lowest possible level is accompanied by a significant increase inT c = 0 (96 K) and critical current density. The possible mechanisms underlying the effect of Pb substitution on the properties of 2212 are discussed.

The process of lithium trapping by excess oxygen atoms in both crystalline and amorphous ${\mathrm{WO}}_{3}$ is studied by first-principles calculations. In both materials, the excess oxygen is incorporated in the bonding network by a peroxide-type bond. In both $c\ensuremath{-}{\mathrm{WO}}_{3}$ and $a\ensuremath{-}{\mathrm{WO}}_{3},$ breaking of this bond makes oxygen states available for the accommodation of the Li electrons. However, only in $a\ensuremath{-}{\mathrm{WO}}_{3}$ is this mechanism accompanied by a strong reduction in total energy as this material has the flexibility to accommodate (incorporate) the extra ${\mathrm{O}}^{2\ensuremath{-}}$ ion.

The tunability of the oxygen stoichiometry in the Ba RE (Cu 0.5 Fe 0.5 ) 2 O 5+ δ double-perovskite structure, stable with rare earth elements RE =Lu–Pr, was studied by both normal-pressure thermogravimetric oxidative (O 2 ) and deoxidative (Ar) post-annealings and high-pressure heat treatments carried out in a cubic-anvil-type high-pressure apparatus. Under reducing conditions the Ba RE (Cu 0.5 Fe 0.5 ) 2 O 5+ δ double perovskite is obtained at δ ≈0 irrespective of the size of the RE constituent. In the structures with RE =Pr and Nd the oxygen stoichiometry can be continuously varied by normal-pressure post-annealings up to δ ≈0.24 and 0.35, respectively, whereas with a smaller rare earth ion, i.e., RE =Lu–Sm, the amount of excess oxygen raises from δ ≈0 only upon high-pressure heat treatment.

We have prepared the superconducting La 2 CuO 4+ δ electrochemically oxidized at 333 K. Each sample is a single-phase superconductor; the low- T c phase ( T c =32 or 36 K, oxidation time=24 h, δ =0.068) or the high- T c phase (45 K, 72 h, 0.093). We have studied the relation between the hole concentration n H , determined by the Hall effect measurement as n H ≡1/ eR H and the valence of Cu 2+ p , determined by the iodometric titration in La 2 CuO 4+ δ . In highly oxidized La 2 CuO 4+ δ , the p /2-dependence of n H has been found to be different from that of the ordinary (La 1− x Sr x ) 2 CuO 4 . Similar phenomena were observed in (La 1− x Sr x ) 2 CuO 4+ δ ( x =0.050, 0.075, 0.100) electrochemically oxidized at 333 K. These results suggest that in La 2 CuO 4+ δ or (La 1− x Sr x ) 2 CuO 4+ δ , the intercalated excess oxygen plays a different role in conduction from Sr in the ordinary (La 1− x Sr x ) 2 CuO 4 .

Selective reduction of NO by CH4 on an In–Fe2O3/H-ZSM-5 catalyst was investigated in the presence of excess oxygen. Compared with In/H-ZSM-5, the In–Fe2O3/H-ZSM-5 catalyst with high Fe2O3 contents showed higher activity in a wide range of reaction temperatures. It was found that the addition of Fe2O3 yielded a promotion effect on CH4 activation. The influence of water vapor on NO conversion was also investigated. The activity of the In/H-ZSM-5 catalyst has been found to be strongly inhibited by water vapor, while the In–Fe2O3/H-ZSM-5 catalyst remained fairly active in the presence of 3.3% steam.

A comparative study on FBC of coal and waste tire was performed from an environmental point of view. A sub-bituminous coal and a nonspecific waste tire blend were used, respectively, as fossil and nonfossil fuels in a fluidized bed combustion (FBC) experimental laboratory installation. The same FBC conditions were carried out keeping constant the air total flow (860 L/h), the percentage of excess oxygen (20%), and varying the combustion temperature (650, 750, 850, and 950 °C). The main objective was to establish the influence of the fuel used in PAH formation and emission. Regarding the PAH formation and emission in FBC, this is the first time that emissions from coal and waste tire combustion are compared. The PAH were collected in different traps and extracted with dimethylformamide (DMF). PAH analysis and quantification were determined by fluorescence spectroscopy in the synchronous mode (FS). Data on polycyclic aromatic hydrocarbons (PAH) are reported and the results obtained show the following: (1) ...

Atomic scale computer simulation based on energy minimization techniques has been used to study excess oxygen accommodation and migration in La2NiO4 + δ. The activation energy for migration in the ac plane is predicted to be 0.29 eV, while the activation energy outside the ac plane, in the b direction is predicted to be 2.90 eV. The activation energies within the ac plane are unaffected by the presence of compensating Ni3+ defects.

The selective catalytic reduction of NO by propylene or CO in the presence of excess oxygen is a system of great technological importance. The effect of Electrochemical Promotion (or Non-faradaic Electrochemical Modification of Catalytic Activity — NEMCA) was used to promote this reaction (C3H6 or CO/NO/O2) on Rh/YSZ catalyst-electrodes. It was found that both the catalytic activity and the selectivity of the Rh catalyst-electrode is affected dramatically upon varying its potential with respect to a Au pseudoreference electrode. Catalytic rate enhancements up to 15000% and 6000% were observed in the case of NO reduction by propylene, while the product selectivity to N2 production is affected significantly (up to 200%) upon positive potential application. Remarkable promotion of the catalytic activity was also observed in the case of NO reduction by CO, since up to 20-fold increases both in catalytic rates and in NO conversion were obtained under NEMCA conditions.

Reduction of NO with ammonia in excess oxygen has been carried out on proton‐form and Cu2+‐exchanged MFI ferrialuminosilicate. Though H‐ZSM‐5 showed very low activity, the framework Al in H‐ferrialuminosilicate greatly enhanced the activity. The framework Al in Cu2+‐exchanged ferrialuminosilicate also enhanced the activity to some extent.

Selective catalytic reduction of NOx by propene has been investigated on Pt-USY and compared to other Pt-catalysts. The catalyst was characterized by XRD, Ar adsorption at 87 K, TEM, and CO chemisorption, and tested in a gas mixture system in excess oxygen. Pt-USY shows an excellent activity in the reaction, with a molar NOx conversion of 90% at 475 K. Stability during time-on-stream and resistance to SO2 and H2O in the feed stream has also been investigated. Pt-USY performs better under lean-burn conditions than other Pt-catalysts on ZSM-5, Al2O3, or SiO2. The selectivity to N2 was similar for all the catalysts (∼30%), the other major product being N2O.

Photoluminescence (PL) study of needle-like ZnO nanorods grown under standard and oxygen-rich conditions is presented. The yellow-orange band at ~580nm increases with excess oxygen during growth. Subsequent annealing in a reducing atmosphere shows the disappearance of this band. The yellow-orange emission is attributed to oxygen interstitials (O"i).

A theory of the isotopic dependence of the hydrogen content in palladium and the excess oxygen content in manganites is formulated. The theoretical results for the first system are obtained without any fitting parameters and reproduce the experimental data within 2–3% error limits in the temperature range from 170K to 1450 K. An exact expression for the magnitude of the effect is also obtained for the second system, but owing to the lack of necessary experimental data, it can only be estimated in order of magnitude.

The structure of a La 2 CuO 4+ y single crystal with the excess oxygen content y =0.03 has been studied by means of neutron diffraction at T =13 K. Although the extra oxygen content of y =0.03 is inside the miscibility gap of La 2 CuO 4+ y (0.01 y Cmca symmetry. It was confirmed that the extra oxygen, O4, is located close to the site (1/4, 1/4, 1/4). The structural parameters for all atoms lay between those previously determined for the oxygen-poor and oxygen-rich phases representing the edges of the miscibility gap, y =0.01 and 0.06, respectively. Our data allow us to conclude that (1) the phase-separated and non-phase-separated La 2 CuO 4+ y compounds are structurally identical, and (2) the crystal structure of La 2 CuO 4+ y changes monotonically when the extra oxygen content changes from 0 to 0.05.

Radiation damage in Bi2Sr2CaCu2O8+δ or Bi(2 2 1 2) by 55 MeV Li3+-beam has been studied from electrical resistivity and X-ray diffraction characterizations. This irradiation increases electrical resistivity and broadens X-ray diffraction lines by generating defects in all samples. But superconducting critical temperature, Tc, is seen to increase for Bi(2 2 1 2) with excess oxygen and decrease for Bi(2 2 1 2) with O-content less than the optimum, that gives maximum Tc. This increase of the superconducting critical temperature on Li-irradiation of O-rich Bi(2 2 1 2) as well as the decrease for low-O Bi(2 2 1 2) is due to O-displacement. This is in agreement with our earlier He-irradiation results.

Polymorphic transitions in Al2O3, tungsten bronzes, 2CaO · SiO2, and ZrO2 are considered. Considering that at high temperatures oxides usually have excess oxygen vacancies, a further increase in their concentration due to introduction of corresponding additives slows diffusion, impedes the polymorphic transition, and stabilizes the phase. Introduction of additives that result in an increased concentration of cation vacancies, on the other hand, accelerates diffusion and facilitates the polymorphic transition.

Polycrystalline samples of Bi 2 Sr 2− x La x CaCu 2 O y and pure Bi2212 with different oxygen content have been prepared and studied by Raman spectroscopy. No frequency change of O Bi A g mode is observed. The O Sr A g mode exhibits remarkable downward frequency shift. The analysis indicates that the content of excess oxygen inserted into the Bi 2 O 2 layer is the important factor causing frequency shift of the O Sr A g mode.

The change of the electronic structure across the metal-insulator transition in a Mott-Hubbard system ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{TiO}}_{3}$ has been investigated by x-ray absorption and photoemission spectroscopy. The results are compared with ${\mathrm{CeTiO}}_{3+\mathrm{\ensuremath{\delta}}},$ where hole doping is achieved by excess oxygen instead of Sr substitution. It is found that additional doped-hole states are created in the insulator gap for both cases, while the density of states at the Fermi level in ${\mathrm{CeTiO}}_{3+\mathrm{\ensuremath{\delta}}},$ is nearly half of that in ${\mathrm{Ce}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{TiO}}_{3}$ at the same nominal doping. This suggests a strong reduction in the mobility of carriers due to cation vacancies produced by excess oxygen.

The DME‐SCR activity was suppressed upon exposure of a γ-alumina catalyst to SO2, in contrast to methanol‐SCR, which remains active at the same surface sulphate coverage. This difference in behaviour is attributed to the limited availability of surface methoxy, which may be regarded as a prerequisite for NOx- reduction over γ-alumina under lean conditions, in the case of dimethyl ether in the presence of SO2.

The phase separation (PS) effect in superconducting ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4+x} (xl~0.04)$ single crystals with low oxygen mobility was studied via $\ensuremath{\mu}\mathrm{SR}$ spectroscopy, high-resolution neutron diffraction, and magnetic susceptibility. Despite the fact that all crystals are inside the miscibility gap $(0.01lxl0.06),$ only crystals with a sufficiently large excess oxygen concentration $x=0.04$ show a macroscopic phase separation according to the neutron-diffraction data. However, in all samples a phase transition to an ordered magnetic state was observed by $\ensuremath{\mu}\mathrm{SR}$ spectroscopy concomitantly with the onset of superconductivity. This effect is treated as a microscopic phase separation which is possibly driven by superconductivity.

We have studied the thermal history dependence of the superconducting properties below and above room temperature (RT) in the ceramic ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4+\ensuremath{\delta}}$ with excess oxygen, which were prepared by annealing in high-pressure oxygen gas or electrochemical oxidation. The diffusion of the excess oxygen is concluded not to occur below RT. In the sample with small \ensuremath{\delta}, the low ${T}_{c}$ (32 or 36 K) superconducting phase appears, of which ${T}_{c}$ is changed by the annealing at about 200 K. This change is presumably due to some phase transition without the diffusion of the excess oxygen. On the other hand, when \ensuremath{\delta} reaches some threshold, another single superconducting phase with high ${T}_{c}$ (45 K), which is stable below 373 K at least, appears. This sample was prepared by the electrochemical oxidation at 333 K for more than 48 h, where the excess oxygen can diffuse. In the sample electrochemically oxidized at RT, both the low- and high-${T}_{c}$ superconducting phases were formed only near the surface area of the sample. These phases were homogenized by annealing at 373 K.

A “nonstoichiometry” mechanism of giant isotope effects in colossal-magnetoresistance manganites and other oxide semiconductors is proposed. It is not related to an anomalously strong electron-phonon coupling in them and is based on the fact that the thermodynamic equilibrium densities of the oxygen vacancies or excess oxygen atoms depend on the mass of the oxygen atom. As the vacancies and excess atoms act as donors and acceptors, respectively, the charge carrier density in oxide semiconductors is isotope dependent. On the other hand, as nonstoichiometric oxygen atoms produce an effective pressure inside the crystal, the difference in the effective pressures for different isotopes can manifest itself as an isotope dependence of their electric and magnetic properties.

The oxygen-isotope effect of the ferromagnetic transition in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ was investigated from $x=20%$ to $x=43%.$ This is the range of the conducting ferromagnetic phase. We find that ${\ensuremath{\alpha}}_{\mathrm{O}}=\ensuremath{-}\ensuremath{\Delta}\mathrm{ln}{T}_{c}/\ensuremath{\Delta}\mathrm{ln}m$ decreases from 0.36 to 0.14 with increasing Ca concentration. A large value of ${\ensuremath{\alpha}}_{\mathrm{O}}=0.83$ was found for $x=20%,$ it is possibly connected with excess oxygen content. The isotope effect decreases with increasing tolerance factor, pointing to the importance of double exchange. The isotope effect at 35% Ca is independent of magnetic field.

Selective reduction of nitric oxide (NO) by ethene in the presence of excess oxygen was investigated using a silver supported on TiO2 (Ag/TiO2) catalyst. Ag/TiO2 showed high catalytic activity for the reduction of NO to N2 and N2O. The activity for the reduction of NO to N2 and N2O was enhanced with an increase up to 3 wt.% Ag loading level. On increasing the concentration of ethene, the catalytic activity for the reduction of NO to N2 and N2O was enhanced. The reduction of NO over Ag/TiO2 catalyst never proceeds without coexistent oxygen.

An incommensurate modulation was observed directly for the first time by transmission electron microscopy in a phase-separated Cu-rich La2CuO4.003 crystal at room temperature and at 93 K. After annealing in Ar atmosphere, both incommensurate modulation and phase separation disappeared. It is concluded that the incommensurate modulation is attributed to the phase separation, while the occurrence of phase separation in the sample with such a low excess oxygen content results from the enhanced antiferromagnetic interaction due to the Cu dopant.

Powder of BaPb x Bi y O z with strictly controlled compositions were synthesized over a wide composition range of x and y . The region where the superconductivity appears to coincide with that of pseudo-cubic structure. In the superconducting phase, the oxygen content was found to exceed 3.00 suggesting that the excess oxygen plays an important role in realizing the superconductivity.

Fe-Al-O films with high electrical resistivities were prepared on polyimide substrates by reactive dc magnetron sputtering in Ar + O2 gases and by RF co-sputtering of Fe and Al2O3. The relationship between the magnetic properties and resistivities of the films was investigated. The films prepared by RF co-sputtering exibited soft magnetic properties together with high resistivities of more than 103μΩcm. After annealing at 380°C for 1 hour under a field of 1 kOe, a coercivity of 1.5 Oe, a resistivity of 2600μΩcm, an anisotropy field of 6 Oe and a saturation magnetization of 10 kG were obtained. These results are considered to be same values as the nano-granular structure reported on Fe-Al-O films prepared on glass substrates. On the other hand, the films prepared by reactive dc magnetron sputtering did not exibit such soft magnetic properties, because the nano-granular structure was disturbed by the presence of excess oxygen during film deposition.

CuMOR catalysts with different Si/Al ratios and copper contents, prepared from the acid and sodium forms, were studied in NO reduction with propene in the presence of excess oxygen. It was observed that the influence of zeolite Si/Al ratio on CuMOR catalytic activity for NO SCR by propene depends on the catalyst copper content, the reverse being also true. For mordenites prepared from the acid form, it was shown that the most active catalyst must have ∼60% of copper exchange, whereas for those prepared from the sodium form, the maximum catalytic activity is obtained for catalysts with 20% of copper exchange. Moreover, it was observed that at low copper-exchange levels, the catalyst prepared from the sodium form exhibits much higher activity than those prepared from the acid form. Although, when the copper-exchange level increases, the effect of zeolite form is less pronounced. Thus, it was indicated that Bronsted acidity does not promote the NO selective reduction by propene.

Thin, discontinuous Pt/Ti films with different film thicknesses on microfabricated conductometric sensors were exposed to ppm levels of hydrogen or propylene at elevated temperatures in the presence of excess oxygen. Exposure to hydrogen at temperatures between 100 and 400°C resulted in a decrease in film resistance, with a trend towards higher response with increasing temperature. Thinner Pt/Ti films (35 A Pt on 65 A Ti) showed larger relative resistance changes than thicker Pt/Ti films (75 A Pt on 65 A Ti). Neither of the films were sensitive to propylene until the temperature exceeded 350°C, coinciding with the onset of catalytic oxidation of propylene. Above 350°C, the film resistance decreased with increasing propylene concentration. Thus, operating the films in different temperature regimes permits differentiation between hydrogen and propylene. Reversible sensor response can be accomplished in the presence of excess gas phase oxygen.

Over the past decade, we have studied in detail the low-energy spin fluctuations in :a 2− x Sr x CuO 4 for x between 0 and 0.18. Our experiments, as well as those by others, have revealed a fascinating interplay between the hole doping, the static and dynamic spin fluctuations and superconductivity. Recently, using electrochemical techniques, we have learned how to produce large single crystals of La 2 CuO 4+ y which are relatively homogenous. In this latter system, the dopants are characterized by annealed rather than quenched disorder. Furthermore, we have demonstrated staging behavior of the excess oxygen analogous to staging in intercalated graphite. We have now succeeded in carrying out measurements of the low-energy spin fluctuations in stage-6 La 2 CuO 4+ y . Specifically, we find that in this system which has T c = 31 K, the spin fluctuations are incommensurate with energy and temperature dependencies very much like those in La 1.85 Sr 0.15 CuO 4 with T c = 33 K. In addition, we find that T c / δ is a constant for high-quality materials in both La 2− x Sr x CuO 4 and La 2 CuO 4+ y , here δ is the incommensurability.

The excess oxygen concentrations of La2NiO4+δhave been measured in 0.00–6.06, 13.33–18.25, or 66.66–71.40 kPa of oxygen in the range 300–1273 K by the desorption method. The electrical conductivities of La2NiO4+δhave been also measured in 1.33, 13.33, 66.66, or 101.33 kPa of oxygen in the range 77.4–1273 K or under a helium atmosphere (1 atm) in the range 77.4–300 K. The mechanism of the metal–semiconductor transition of La2NiO4+δis discussed on the basis of the excess oxygen concentration and the electrical conductivity data. The metal–semiconductor transition of La2NiO4+δis explained by the carrier concentration and the activation energy changes associated with the incorporation of excess oxygen.

The Cu 2P3/2 photoelectron spectra were acquired to study the coordination state and oxidation state of Cu in ZSM-5 in the NO reduction by propene in the presence of excess oxygen. Two peaks at hig...

Systematic Mn K-edge x-ray-absorption spectroscopy (XAS) measurements on samples of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ca}}_{\mathrm{x}}$${\mathrm{MnO}}_{3}$ are reported. Detailed results on the chemical shift and pre-edge feature spectral strength (both indicators of the Mn d-hole count) are discussed. The overall chemical shift across the series is compared to standard materials and is consistent with the identification of the endpoint perovskites with the ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Mn}}^{4+}$ states. The detailed compositional dependence of the chemical shift and the strength of the pre-edge feature both indicate a uniform Ca-induced increase in the Mn d-hole count for xg0.2 and an anomalous break from this behavior for x values less than x\ensuremath{\approx}0.2. Careful x-ray-diffraction measurements of the lattice parameter variation are also found to manifest changes near x\ensuremath{\approx}0.2 and the chemical shift results are shown to scale with the lattice parameter results. Additional XAS results on air prepared and oxygen annealed samples reveal a variation in the chemical shift response to excess oxygen across this series. These XAS results are discussed in terms of the important Mn d-hole count variation across this system.

The hopping conductivity of La2CuO4+δ single crystal with excess oxygen has been studied. It is found that the transition from variable-range hopping (with the temperature dependence of resistance R∝exp(T0/T)1/4) to simple activation conductivity (R∝exp(Δ/kT)) occurs at a temperature lower than 20 K. This transition is accompanied with significant changes in the behavior of magnetoresistance and current–voltage characteristics. It is shown that such a behavior of hopping conductivity below 20 K is due to the presence of superconducting inclusions in insulating sample due to phase separation of La2CuO4+δ. The observed peculiarities in the conducting properties are in good agreement with the known effects of competition between electron localization and superconductivity in homogeneous systems.

X-ray structure analyses were performed with HgBa2CuO4+δ and Hg1−xPbxBa2CuO4+δ single crystals. The onset of the superconducting transition of the crystals ranges from 78–92 K. Hg-1201 crystallizes with space group P4/mmm and has lattice pafameters a = 3.8907(2) A and c = 9.556(1) A . The structure was refined to R = 0.023 (wR2 = 0.036) in the ideal 1201 type with an excess oxygen content of 6(2)% and an occupancy of 97% at the Hg site. Pb-doping decreases the lattice parameters to a = 3.8836(2) A and c = 9.553(1) A , and the refinement converged at R = 0.042 (wR2 = 0.088). Pb atoms are shifted by 0.5 A to (0.14, 0, 0) and the excess oxygen atom O(3) by 0.45 A to (0.38, 1 2 , 0). It has not a well defined position in the lattice, but is distributed randomly in a ring-like configuration around the ( 1 2 , 1 2 , 0) site, supporting a Pb clustering model. Rather high anisotropic temperature factors U11 and U22 of Hg and apical O(1) atoms are observed, which are also present in higher members of the Hg(Pb)-12(n − 1)n series. They are discussed in terms of corrugated OHgO bonds. Comparison with other structure refinements of 1201 shows a correlation of the transition temperature with the position of the Ba atom, which seems to be a good indicator for the hole doping evel in 1201.