Oxygen

About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.

Charge compensation mechanisms in La-doped BaTiO3

Abstract: The mechanism of doping BaTiO3 with La has been investigated by a combination of X-ray diffraction, electron probe microanalysis, scanning and transmission electron microscopy and impedance measurements Phase diagram results confirm that the principal doping mechanism involves ionic compensation through the creation of titanium vacancies All samples heated in oxygen at 1350–1400°C are electrical insulators, consistent with an ionic compensation mechanism Samples heated in air or atmospheres of low oxygen partial pressure, at similar temperatures, lose a small amount of oxygen and this gives rise to a second, electronic compensation mechanism in addition to the main, ionic compensation mechanism; as a result, samples are dark-coloured and semiconducting The change from insulating to semiconducting behaviour is reversible, by changing the atmosphere on heating at 1350–1400°C We find no evidence for any changes in cationic composition of the BaTiO3 solid solutions arising from changes in oxygen content

Electrode properties of Ln2NiO4 + δ ( Ln = La , Nd , Pr ) AC Impedance and DC Polarization Studies

Abstract: The perovskite-type materials, Ln 2 NiO 4+δ , were prepared by a modified Pechini method and their electrochemical properties investigated using ac impedance and dc polarization methods from 300 to 800°C under different oxygen partial pressures. Schouler methodology based on the frequency relaxation has been used to assign different electrochemical processes. A transfer process related to oxygen ions moving between the electrolyte and electrode interface was found in the mixed ionic and electronic conducting electrode/electrolyte system. The study shows that the Nd 1.95 NiO 4+δ compound exhibits promising electrode properties due to its high chemical stability and low polarization resistance. The oxygen diffusion process is the rate-limiting step at low oxygen partial pressure, whereas the charge-transfer process becomes more important at higher oxygen partial pressure.

Leakage current of multiferroic (Bi0.6Tb0.3La0.1)FeO3 thin films grown at various oxygen pressures by pulsed laser deposition and annealing effect

Abstract: Thin films of multiferroic (Bi0.6Tb0.3La0.1)FeO3 were grown on Pt∕Ti∕SiO2∕Si substrate under various oxygen pressures by pulsed laser deposition technique. X-ray diffraction patterns show that the crystallinity of the thin film is improved with decreasing depositing oxygen pressure and the thin film grown at a lower oxygen pressure of 0.01torr exhibits a single perovskite phase with preferred (001) orientation. Leakage current of the as-deposited thin films decreases with decreasing grown oxygen pressure. Significantly, the leakage current of the thin films can be reduced largely by an annealing process at 800°C with flowing oxygen. The annealed thin films show a relatively high resistivity and stable polarization loops with double remnant polarization of about 3μC∕cm2. The conduction properties of the thin films have been well analyzed, and it is indicated that the dominant conduction mechanism is the space-charge-limited conduction for the thin film grown at higher oxygen pressure and the Poole-Frenkel ...

Intra- and extracellular measurement of reactive oxygen species produced during heat stress in diaphragm muscle.

Abstract: Skeletal muscles are exposed to increased temperatures during intense exercise, particularly in high environmental temperatures. We hypothesized that heat may directly stimulate the reactive oxygen...