Microstructure and electrical conductivity of 3Y-TZ/Al2O3 composites

Various amounts of Al2O3 (0.25, 0.5 and 1.0mol%) were added to tetragonal polycrystalline material (3YTZP), prepared using the hydrothermal crystallization method. The effects of the added amount as well as the sintering temperature on the microstructure and electrical properties of the 3Y-TZP/Al2O3 composites were investigated. The alumina addition was found to affect the microstructure of the 3Y-TZP samples obtained after sintering at 1400 or 1500?C only to a slight extent. The lowest values of the blocking factor, which represents the contribution of grain boundary resistivity to the total resistivity of a polycrystal, were observed for the 3Y-TZP with Al2O3 additions of 0.25 or 0.5mol% at measurement temperatures of 550 and 600 ?C. The study proves that the 3Y-TZP/Al2O3 should be taken into consideration as solid electrolyte in the intermediatetemperature solid oxide fuel cells.

Improved definition of gas sand using elastic impedance attribute on an avo data over an x field, Nigerian Niger delta

Elastic impedance (EI) inversion is considered one of the newest methods being used today in geophysical interpretation. Preliminary interpretation carried on the well logs revealed a hydrocarbon bearing sand from 8780 to 8900 ft. The average porosity value is 39% which suggest good porosity values for oil and excellent for gas reservoirs. The matched total resistivity values are likewise very high at about 90 Ωm with a very low density at that depth. The logs were modelled by creating the EI near and EI far logs from the input Vp, Vs and density logs at a defined angle of incidence of 2.5 for near angle and 45.0 for far angle. The EI Far log is lower than the EI Near log in the interpreted depth but higher in the rest of the log. This is further revealed in the crossplot showing the mapped gas sand at depth between 8780 and 8900ft. Two Range limited stack were created from the seismic gathers with the first/near offset stack at 64m and second/far offset stack at 196m. From each stack, a model each was created to get the near EI model and far EI model respectively from which inversion was done to generate the near and far inversion results. There is an improved definition of the gas sand on the far angle inversion with a stronger contrast represented by low values at the mapped seismic time window which corresponds to the mapped gas sand at same depth. This was further revealed on the crossplot. Inserting the crossplot on the near-Inversion volume with the mapped zone, the visible top of gas on the zone of interest was noticed. This zone confirmed where the elastic impedance at far-offsets is lower than the elastic impedance at near-offsets moreover agreed with the Elastic Impedance results on the logs. The Elastic Impedance attribute and its inversion technique has shown it is a strong and suitable tool in exploitation of gas zones as it has optimized the area of the gas zone approved by well logging process.

SINTERING AND ELECTRICAL PROPERTIES IN AIR FOR A-SITE DEFICIENT (Sr0.7La0.3)1-yTiO3 PEROVSKITE SAMPLES WITH AND WITHOUT TiO2 PHASE

The sintering and electrical properties of A-site-deficient perovskites, namely, ( Sr 0.7 La 0.3)0.85 TiO 3 with TiO 2 and ( Sr 0.7 La 0.3)0.88 TiO 3 with a single perovskite phase, were investigated in air using powders synthesized by solid-state mixing. ( Sr 0.7 La 0.3)0.85 TiO 3 showed much higher sintering characteristics than ( Sr 0.7 La 0.3)0.88 TiO 3. The relative density of ( Sr 0.7 La 0.3)0.85 TiO 3 reached 96% at 1500 °C with zero holding time, but decreased with increasing holding time, owing to pore formation inside the sample. The resistivity of ( Sr 0.7 La 0.3)0.85 TiO 3 was lower than that of ( Sr 0.7 La 0.3)0.88 TiO 3 at measurement temperatures ≤600 °C, although the reverse was observed at temperatures ≥700 °C. Because the total resistivity of ( Sr , La ) TiO 3 perovskites should be governed primarily by grain boundary resistivity at low temperatures, ( Sr 0.7 La 0.3)0.88 TiO 3 with many grain boundaries showed higher resistivity, compared to that of ( Sr 0.7 La 0.3)0.85 TiO 3.

INTERESTING RESISTIVITY BEHAVIOR OF THE Ag–Ni–Si SILICIDE FILMS FORMED AT 850°C BY RAPID THERMAL ANNEALING OF THE Ag–Ni/Si FILMS

The temperature-dependent resistivity measurements of our Ag – Ni – Si silicide films with 51–343 nm thicknesses are studied as a function of temperature and film thickness over the temperature range of 100–900 K. The most striking behavior is that the variation of the resistivity of the Ag – Ni – Si silicide films with temperature exhibits an unusual temperature-dependent behavior with respect to those of the transition and untransition metals. Our measurements show that the total resistivity of the Ag – Ni – Si silicide films increases linearly with temperature up to a Tm temperature at which resistivity reaches a maximum thereafter Tm decreases rapidly and finally to zero at ~850 K. Tm temperature is found to decrease with decreasing film thickness. We have shown that in the temperature range of 100-Tm K, electron–phonon resistivity and grain boundary resistivity components responsible for the total resistivity increase. But the grain boundary scattering is dominant mechanism for the resistivity increase in our Ag – Ni – Si silicide films.

The thermal fission-induced crystalline-to-amorphous transformation in U6Fe

The crystalline-to-amorphous transformation in U6Fe produced by thermal fission fragment damage was studied using resistivity and differential scanning calorimetry. The results are described in terms of a model of radiation-produced defect buildup in the crystalline matrix followed by transformation of small regions to an amorphous phase when a critical local defect concentration is reached. This can occur directly in a single cascade or from cascade overlap. The total resistivity is modeled assuming an inhomogeneous media consisting of a crystalline matrix containing a dose-dependent concentration of defects and amorphous zones. The crystallization behavior is initially, starting at Tc = 388 K, a kinetically limited process of shrinkage of amorphous zones that gradually transforms to nucleation and growth in fully amorphous material at Tc = 555 K.

Two OPW calculations of electronic transport properties of copper below 20 K

The results of numerical calculations of the electrical and thermal lattice resistivity of copper at temperatures (T) below 20 K are presented. We have calculated the matrix element for electron–phonon scattering using two OPW electronic states and the Born – von Karman method of determining the phonon frequencies and eigenvectors. We have used the eight-cone model of the Fermi surface in which necks intersecting the Brillouin zone and the spherical belly regions are both present.The lattice electrical resistivity is calculated for two limiting cases. In the first case the resistivity is that expected when no impurities are present in the metal. In the second case the impurity resistivity is taken to dominate the lattice resistivity. We show that the T3 behaviour of lattice resistivity recently observed experimentally below 10 K can be understood as occurring when the temperature is lowered and the total resistivity moves from the lattice dominated to impurity dominated case.The results of a preliminary calculation, in which a more exact Fermi surface and 27 APW electronic states were used, are also described.

A SURFACE LAYER MODEL FOR THE TOTAL RESISTIVITY OF THERMOMETRIC-GRADE PLATINUM WIRE

A model for the temperature dependence of the total resistivity of thermometric-grade platinum wire is developed. The evidence supports as a basic model the two-electronic conduction-band theory of Sondheimer and Wilson. However, in the small-diameter (~80 μm) wire, here considered, surface contamination would lead to deviations from the simple model. A theory of multiple conduction bands, due to surface contamination, has been developed. The theory enables us to infer, from known calibration data on platinum resistance thermometers, that there are two regions of contamination. One is a region of heavily concentrated impurity over a few atomic layers at the surface, which accounts for variations in resistivity near 700 °K. The other is a subsurface layer about 0.1 μm thick with about 0.1% impurity level, which accounts for variations in resistivity in the region of 90 °K.

The propagation of electrons in a strained metallic lattice

The propagation of electrons in a strained metallic medium is studied by a perturbation technique in which the perturbing potential is proportional to the elastic strain and not, as in the usual treatment, to the displacement. For slowly varying strains the perturbing potential is a deformation potential of the type introduced by Bardeen & Shockley (1950), in which the periodicity of the lattice does not appear explicitly. In the approximation of nearly free electrons, the contribution of the ionic lattice to the deformation potential depends only on the dilatation and not on the shear components. This potential is modified by a flow of electrons from the compressed regions of the lattice to the expanded regions. The resulting potential depends only on the Fermi energy of the electrons and not on their interaction with the lattice of ions. In a higher approximation, the effective mass of the electrons depends on their interaction with the ionic lattice. The contribution of this term is comparable with that already considered, and the shear components of the strain also influence the deformation potential. The method is applied to estimate the electrical resistivity produced by dislocations of edge and screw types present in sodium and copper. In copper screw dislocations add appreciably to the total resistivity.