The effect of gas atmospheres on resistivity of indium tin oxide films at high temperature

The effects of heat treatment in Q₂, O₂ and N₂, and Ar gases on the high temperature (500 C) electrical resistivity of indium tin oxide (ITO) film 52 nm thick prepared by chemical spray pyrolysis method were studied. The partial oxygen pressure effect on the resistivity was found to be to . The resistivity changes for cyclic exchange of O₂ by Ar gas at 500 C. These lead to the conclusion that chemisorption of oxygen atoms in the film surface is dominant for this thin film, for thicker films such as 640 nm oxygen diffusion is found to occur. The Langmuir model of the monolayer isothermal adsorption of oxygen atoms in the surface is applicable to the rapid change of resistivity.     

Evaluation of stress-rupture strength with a complex stressed state for nickel alloys with a polycrystalline and single-crystal structure

A criterion is suggested for estimating stress-rupture strength with a complex stressed state for alloys with a polycrystalline structure

Transmission electron microscope study of a directionally solidified Cu-MgCu2 eutectic

The crystallography and the interface structure of a unidirectionally solidified Cu-MgCu₂ eutectic alloy have been examined by transmission electron microscopy. The microstructure of the eutectic was found to be lamellar and regularly interrupted by faults. The preference of the particular orientation relationship could not be explained by relative atomic densities of the planes comprising the interface. Based on the defect contrast observed and extinction distance calculations, it is suggested that the fine array of defects observed at the interface may be characterized as steps with step vectors parallel to or Dislocations were also observed at the interface but they were rarely regular.     

Anisotropic flow and fracture in beryl [Be3Al2(SiO3)6]

Flow and fracture resulting from Vickers indentation testing on {0 0 0 1} and {10 0 } planar orientations have been examined. Flow characterized by indent shape differentiation was analysed to belong to the slip system with planes of the types { 10 0} and {11 0}. The ensuing fracture paths were resolved to propagate along {1 0 0} and {1 1 } cleavage planes whileK _c values obtained for them were 0.196 and 0.248 MPam^1/2, respectively.     

Defect structure of acceptor-doped calcium titanate at elevated temperatures

The defect structure of acceptor (Al or Cr)-doped polycrystalline calcium titanate was investigated by measuring the oxygen partial pressure dependence (at 10° to 10–18 atm) of the electrical conductivity at 1000 and 1050° C. The observed electrical conductivity data were proportional to for the oxygen pressure range < 10^–10 atm and proportional to for the oxygen pressure range ( 10^–7 atm. The conductivity values were observed to increase with the acceptor concentration in the p-type region with the shift in the conductivity minima towards lower oxygen partial pressure. The absolute value of the electrical conductivity in the acceptor-doped samples were lower in the n-type region compared to the values in the undoped CaTiO₃. Aluminium and chromium were found to be equally effective in acting as acceptor impurities in CaTiO₃. The defect chemistry of CaTiO₃ is dominated by the added acceptor impurities for the entire oxygen partial pressure range used in this investigation.     

Aqueous Electrolytes at Near-Critical and Supercritical Temperatures

The aqueous electrolyte systems are of great interest both geologically and industrially. Equations of state were developed recently for these systems; they are based on theoretical modeling for mixtures of hard spheres with appropriate diameters and dipole moments for H₂O, NaCl, and KCl and with a quadrupole moment for CaCl₂. Empirical terms are added as required to fit the available experimental data. The fit to the compositions and densities at equilibrium of the saturated vapor and liquid constitutes a severe test, in addition to properties in the single-phase regions. Temperatures range upward from 300°C for NaCl and KCl and from 250°C for CaCl₂ for these equations. Complications from hydrolysis and alternate equations valid at lower temperatures are discussed briefly. In addition, there is a very important theoretical aspect relating to the general phase diagrams. With the high ratio of critical temperatures of the salts to that of water, complex diagrams involving liquid–liquid phase separation near the critical point of water are expected. But no such effect is observed experimentally; instead, one finds simple type I phase diagrams. This is particularly clear in the case of , where the database is very accurate and extends above 1000 K.     

Computer-aided design of small patch antenna using (Al, Mg)TaO2 ceramics

The microwave dielectric properties of (AMT) ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. ( and ( have orthorhombic and tetragonal structure, respectively. As ( concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As ( concentration increased, the grain size, dielectric constant and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency changed from negative to positive. The of was realized at x=0.65 and the Q · f _O value and for this composition were 112 470 GHz and 26.1, respectively. Newly developed dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation.     

Determination of standard Gibbs energies of formation of ternary oxides in the system Co-Sb-O by solid electrolyte emf method

An isothermal section of the phase diagram of the system Co-Sb-O at 873 K was established by isothermal equilibration and XRD analyses of quenched samples. The following galvanic cells were designed to measure the Gibbs energies of formation of the three ternary oxides namely CoSb₂O₄, Co₇Sb₂O₁₂ and CoSb₂O₆ present in the system.

Electrical conductivity in non-stoichiometric titanium dioxide at elevated temperatures

The electrical conductivity of polycrystalline titanium dioxide prepared by a liquid mix technique was measured for the oxygen partial pressure range of 10° to 10^–19 atm and temperature range of 850 to 1050° C. The data were found to be proportional to the –1/6 power of oxygen partial pressure for the oxygen pressure range 10^–19 to 10^–15 atm, and proportional to for the oxygen pressure range >10^–15 atm. The region of linearity where the electrical conductivity varied as the –1/4 power of increased as the temperature was decreased. There was evidence of p-type behaviour for 10^{ - 2}$$ " align="middle" border="0"> atm in the temperature range 950 to 850° C, although the measured data were insufficient to assign a pressure dependence. Electrical conductivity minima in the log against log plot moved to lower as the temperature was decreased in the range 950 to 850° C. The measured oxygen pressure dependence of electrical conductivity in the lowest region supports the oxygen vacancy defect model. The observed data are consistent with the presence of very small amounts of acceptor impurities. A binding energy of 0.67 eV between the acceptor impurity and its compensating oxygen vacancy was also determined.     

Thermal diffusion ratio of a3He/4He mixture near its λ transition: The onset of heat flush

We present experimental data on the thermal diffusion ratioK _T for a 15 molar % mixture near its transition obtained from measurements of the convection velocity of a mixture contained in a vertical column. The physical nature of the normal modes of heat and mass transfer near the transition is discussed. One possibility that arises from this discussion is that the temperature dependence ofk _T may be such that , where is the value ofk _T at the transition andD is the mass diffusion coefficient. There is limited support for this conjecture by the data over a restricted temperature range.     

Hydrogen reduction of Cu-Mn-Fe-O spinel solid solutions

The crystal-chemical transformations accompanying the hydrogen reduction of Cu_xMn₁ - xFe₂O₄ (x = 0.2, 0.5, 0.8) solid solutions are investigated, and general equations describing these processes over the entire composition range (0 x 1) are derived. The results on the character of the processes involved differ radically from earlier findings. The equilibrium oxygen pressure is evaluated for the low-oxygen phase boundary of the spinel solid solutions throughout their stability region. For solid solutions, which are of practical interest, the data are well represented by the equation , which is of importance in controlled synthesis of single-phase materials in this system.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 332–338.Original Russian Text Copyright © 2005 by E. Zinovik, M. Zinovik.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

On a plate supported by an elastic foundation and containing a finite crack

Using an integral formulation, the equation for a plate resting on an elastic foundation, of a spring constant k and containing a crack of length 2c, is solved for the Kirchhoff bending stresses. The inverse square root singular behavior of the stresses peculiar to crack problems is obtained. Furthermore, this singularity may be related to that found in an unsupported plate by where a is for small values of the parameter is a positive constant.

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Zusammenfassung Für eine auf einem elastischen Fundament (Elastizitätskonstante k) ruhende Platte, welche einen Riß der Länge 2c aufweist und Kirchhoff Biegebeanspruchungen ausgesetzt ist, konnte die Gleichung mit Hilfe einer Integralformel gelöst werden.Es ergibt sich das den Rißproblemen eigene singulare Gesetz des umgekehrten Verhältnisses zur Quadratwurzle. Außerdem kann these Singularität mit der für eine nicht gestützte Platte ermittelten über die Gleichung: in Zusammenhang gebracht werden, wobei a für kleine Werte des Parameters eine positive Konstante ist.

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Résumé A l'aide d'une formule d'intégration, on a résolu l'équation d'une plaque reposant sur un support de constante élastique k, comportant une fissure de longueur 2e, et soumise à des contraintes de flexion de Kirchhoff. On aboutit à une distribution des contraintes dont l'amplitude varie en raison inverse du carré de la distance, comportement singulier propre aux problèmes de fissuration.En outre, cette singularité pent etre mise en balance avec celle que l'on trouve dans une plaque non supportée, par l'expression: où a est une constante positive pour de petites valeurs du paramètre .

     

Effect of phosphorus additions on the spacing between primary silicon particles in a Bridgman solidified hypereutectic Al-Si alloy

The effect of 100 ppm addition of phosphorus on primary silicon particle number density per unit area N _A and corresponding interparticle spacing is reported for a Bridgman solidified Al-20 wt%Si base alloy. The phosphorus (added as Al-Fe-P base or Al-Cu-P alloys) results in a factor of 3 increase in N _A and a factor of 2 reduction in for the range of conditions studied. In its absence the results conform to = 256 ± 24 m (K/s)_1/3 where is cooling rate during solidification in good agreement with earlier data. When published data on the effect of 0.02 to 0.2 wt%P are included the combined results are well represented by = 250 – 215 (wt%P)^0.17 ( in m, in K/s).     

Effect of PFT substitution on dielectric properties of PFW-PFN perovskite ceramics

Perovskite phase formation and dielectric characteristics of ceramic system with addition of were investigated in order to examine the influence of . The ceramic system powders were synthesized via a B-site precursor route. Peculiar behaviors of frequency dispersion in dielectric constant spectra in the paraelectric region were observed due to increasing conductivity. Lattice parameters, dielectric maximum temperatures, and maximum dielectric constants increased with increasing content.     

Electrical conduction of partially stabilized zirconia Zr0.94Ca0.06O1.94 as a function of temperature and oxygen partial pressure

Partially stabilized zirconia (PSZ), Zr_0.94Ca_0.06O_1.94was prepared by a hot kerosene drying method and a conventional oxide wet-mixing method. The total d.c. conductivities of these zirconia specimens were measured by the three-terminal technique as a function of temperature in the range 1088 to 1285 K and oxygen partial pressure in the range 1 to 10^–24 bar. The specimen prepared by the hot kerosene drying method showed near oxygen ion conduction with four times higher conductivity than the specimen prepared by the conventional mixing method at T=1088–1285 K and bar. The higher oxygen pressure conductivity tended approximately towards a to dependence, indicative of p-type conduction, whereas the lower oxygen pressure conductivity tended to be virtually independent of oxygen pressure, indicative of oxygenion conduction. The activation energy was found to be 130 kJ mol^–1 at T=1088–1285 K, bar (air) for pure electron-hole conduction and 153kJ mol^–1 at T=1088–1285 K for ionic conduction.     

Phonon Vibration and Conduction of La2 ? xSrxCuO4 ? δ and La1.85 ? xSr0.15 + xCu1 ? xCoxO4 ? δ

Polycrystalline samples La_{2 – x} Sr _x CuO_{4 –} (0.06 x 0.5) and La_{1.85 – x} Sr_{0.15 + x} Cu_{1 – x} Co _x O_{4 –} (0 x 1) were synthesized by a conventional solid state reaction method. The structure, phonon vibration, and conduction were investigated by means of XRD, infrared (IR) spectra, and resistance. It is found that the increase of itinerant hole carriers could mask the in-plane stretching vibration mode (689 cm^–1). The softening of the phonon vibration mode gives an index of the weakening of hybridization. The distortion of CuO₆ octahedron and the microstructural inhomogeneity induced by Co doping lead to the widening of the IR absorption peaks.     

Field Dependence of the Superfluid 3He A 1 and A 2 Transitions

We present new results on the magnetic field dependence of the superfluid transition temperatures of the A ₁ and A ₂ phases of ³He. The transition temperature has been measured up to 15 T, the up to 12 T, at the melting pressure. The temperature was measured by an in situ field independent glass thermometer. The results are in agreement with extrapolations from earlier experiments, and with calculations of the splitting versus magnetic field. We were also able to obtain an estimate of the quadratic terms of the splitting, and of each of the transition temperatures. The measured quadratic terms are smaller than calculated, the negative coefficient for the quadratic term being quite unexpected.     

Structural features of Σ = 19, [110] GaAs tilt grain boundaries

= 19, [110] tilt grain boundaries have been observed to facet parallel to particular planes; the facets lie along _A/ _B, ( )_A/ )_B and ( )_A/( )_B. The structural unit of the = 19 ( )_A/( )_B [110] boundaries consists of 5- and 7-member rings, which are similar to the core structure of a/2[110] edge dislocations. The polarities in each grain on either side of the boundaries has been confirmed by CBED methods; a lower number of anti-site type cross-boundary bonds occur along the boundaries compared to when the polarity of one grain is reversed. The presence of 7-member rings and anti-site cross-boundary bonds results in a more open atomic structure at the boundary, shortening the distance between the first and the second {331} atomic planes from the boundary plane by 40%.     

Decay of 175Hf and 181Hf

Nuclear-physical properties of ¹⁷⁵Hf and ¹⁸¹Hf produced by neutron irradiation of natural hafnium in the SM-3 nuclear reactor were studied. The X-ray and -ray spectra were measured with high-energy-resolution HPGe and Ge(Li) detectors. The half-lives T1/2 (days) were determined: ¹⁷⁵Hf 71.9±1.3 and ¹⁸¹Hf 42.12±0.25. The relative intensities (rel. units) of the -ray lines (keV) of ¹⁸¹Hf are as follows: 133.03, 54.0±1.6; (136.28 + 136.86), 8.9±0.3; 345.919, 20.4±0.6; and 482.193, 100. The ratios of the intensities in the X-ray spectrum were measured: , , , and .     

On primitive and free roots in a finite field

In this paper them-dimensional extension of the finite field of orderq is investigated from an algebraic point of view. Looking upon the additive group as a cyclic module over the principal ideal domain , we introduce a new family of polynomials over which are the additive analogues of the cyclotomic polynomials. Two methods to calculate these polynomials are proposed. In combination with algorithms to compute cyclotomic polynomials, we obtain, at least theoretically, a method to determine all elements in of a given additive and multiplicative order; especially the generators of both cyclic structures, namely the generators of primitive normal bases in over , are characterized as the set of roots of a certain polynomial over .