Oxygen Vapor Pressure Research Articles

Synthesis and Electrical Properties of Nd2(WO4)3–SiO2 Composites

t—The (1 – x)Nd2(WO4)3–xSiO2 composites where the silicon oxide mole fraction is x ≤ 0.5 were manufactured by the solid-phase method. The phase compositions of the composites and their thermodynamic stability were verified by X-ray powder diffraction and thermogravimetry, respectively, in combination with differential scanning calorimetry (DSC). The morphology of the composites was studied by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis. The electrical conductivity of the composites measured by electrochemical impedance was studied as functions of temperature, oxygen vapor pressure, and the amount of silicon oxide (the dispersed additive). The sums of ion transference numbers were studied as a function of temperature by the EMF method; the ionic character of conduction in the composites was found. The composite-conductivity effect was found to occur in the studied system: additions of 30 mol % nanosized silica to neodymium tungstate increased the ionic conductivity by more than two orders of magnitude.

(Invited) Towards the Realization of Bulk Dynamic Strain By Vertically Aligned VO2 Nanowire Hybrid Arrays

Significant epitaxial strain (~1%) is conventionally believed to exist only below the critical thickness limit at tens of nanometer scale, which greatly hinders the possible applications of strain engineering. The development of nanocomposite materials recently attempts to overcome the barrier by the inclusion of instantaneous phase separation between two materials during growth that ends up with a larger surface area, thus promoting large-scale strain. Here as a step forward, we report the growth of vertically aligned VO2 hybrid nanowire arrays that circumvents the pairing requirements for common nanocomposite and at the same time introduces the dynamic bulk strain by triggering the VO2 phase transformation. By controlling the growth temperature and oxygen vapor pressure, dense arrays of VO2 nanowires are obtained via a Chemical Vapor Deposition method. The ZnO/VO2 and BaTiO3/VO2 nanohybrid was then obtained by radio frequency sputtering. By varying the temperature to trigger the VO2 metal-insulator transition (MIT), we were able to dynamically strain the semiconductor overlayer. By studying both the single core-shell nanowire and the VO2 hybrid by photoluminescence and Raman spectroscopy, we show sound evidence of the dynamical strain from MIT. The utilization of phase transition from strongly correlated oxides thus provides a very promising approach for the realization of strain at bulk.

Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

Engineering of nested Fermi surface and transparent conducting p-type Delafossite CuAlO 2: possible lattice instability or transparent superconductivity?

Based on ab initio electronic structure calculation using a super-cell FLAPW method, we propose a new valence control method for the fabrication of low-resistive p-type and transparent conducting oxides of Delafossite CuAlO 2. We propose a Cu-vacancy doping method with decreasing the Cu-vapor pressure and with increasing the oxygen vapor pressure, or, Be- or Mg-acceptor doping method at the Al-site with decreasing the Al-vapor pressure and with increasing the Cu-vapor pressure. The heavily doped p-type CuAlO 2 indicates the two-dimensional nested Fermi surfaces, which originate from the layered O–Cu–O dumbbell. Nested Fermi surfaces may cause possibly a lattice instability or a transparent superconductivity rather than magnetism.

Investigation of Oxidation Process of Ultrathin Amorphous and/or Nano-Crystalline Silicon Films

AbstractA series experiments were conducted and reported here on how to employ quartz crystal microbalance (QCM) as a highly mass sensitive sensor to study a-Si film and Si nanocrystals oxidation under ambient oxygen. An experimental calibration procedure has been developed to prevent problems with QCM systems during routine study. With the help of pulsed laser deposition (PLD) technique, one can purposely deposit a thin layer of a heavy element as an insitu calibrant which can be analyzed by RBS quantitatively for QCM. The errors resulted from manufacture's sensor, non-repeatable sensor mounting and handling, temperature cycling history from run to run and so on will be effectively eliminated. Our preliminary results indicate that the oxidation process of a-Si thin films has two stages. A fast oxidation associated with surface and near surface oxidation followed by a slow oxidation. The former is depends on the oxygen vapor pressure in the chamber and the later is oxygen diffusion controlled process.

Basal plane oxygen vapor pressure of Co-doped YBa2Cu3O7−δ

Transport data for YBa2Cu3−xCoxOz thin films, with x=0.3, 0.5, 0.75, and 1.0, are reported as a function of annealing history in O2 and O2/O3 at temperatures ranging from 200 to 500 °C. For x=0.3 and 0.5, O2/O3 anneals resulted in maximal Tc’s significantly higher than any previously reported, while in all cases the annealing substantially increased the film’s conductivity. Subsequent anneals in O2 resulted in oxygen loss, demonstrating that these materials have a much higher oxygen vapor pressure in the well-oxygenated state than YBa2Cu3O7−δ.

The effect of magnetic fields on the vapor pressure of liquid oxygen

Magnetic effects on paramagnetic oxygen vapor pressure have been investigated under fields of up to 7 T and at temperatures of 65.0 K, 77.4 K and 84.1 K. Experimental data were carefully corrected, with emphasis on the magnetic pressure acting on the sample liquid. It was found that our data clearly exceed those of Meachin and Biddulph, and are consistent with theoretical estimates obtained considering the antiferromagnetic exchange interaction between O 2 spins.

An Improved Oxygen Vapor Pressure Representation

Oxygen vapor pressure measurements reported in the literature have been critically evaluated and the most consistent and reliable of the data sets have been correlated with a vapor pressure equation. However, the data were first adjusted for temperature scale differences to conform with the IPTS-68 temperature scale. "Best" values for the oxygen triple point and critical point parameters were selected for use as indirect constraints in the equation. Pressures obtained from this equation are compared to corresponding values calculated from other published oxygen vapor pressure equations. A new value for the critical pressure of oxygen of 5.0432 MN/m2 (49.772 atm) is given.

High‐Pressure Experiments on Yttrium Iron Garnet

High‐pressure‐high‐temperature experiments carried out on YIG and on 3Y2O3+5Fe2O3 mixtures gave expected results and do not corroborate the recent report by Shimada, Kume, and Koizumi indicating the existence of a “dense ferrimagnetic perovskite allotropic form of yttrium iron garnet.” The results of experiments by Marezio, Remeika, and Jayaraman on the high‐pressure decomposition of synthetic garnets are discussed. The garnet {Y3}[Sc0.6Fe1.4](Fe3)O12 is more stable than YIG under the same conditions of pressure and temperature; this alone disproves the Marezio et al. hypothesis relating stability vs pressure to ionic site preference. The stability of YIG is more sensitive to oxygen fugacity at high temperatures and atmospheric pressure than are those of YAG and YGaG. Thus relative compressibility and equilibrium oxygen vapor pressure are the important parameters.