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1 Mar 1959

Volume 30, Issue 3, pp. 273-455

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Electron Beam Density Probe for Measurements in Rarefied Gas Flows

F. C. Hurlbut

J. Appl. Phys. 30, 273 (1959); http://dx.doi.org/10.1063/1.1735151 (7 pages) | Cited 2 times

Online Publication Date: 16 June 2004

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It is the purpose of this report to describe an instrument for the determination of densities in rarefied gas streams which utilizes the attenuation of an electron beam. The electron beam in passage through a rarefied gas becomes scattered in a number of elastic and inelastic processes, and decays to a fraction of its initial intensity in the distance of a few electron mean free paths. Where the optical aperture of the detector is suitably small, the familiar linear absorption law applies. The mass absorption coefficient in this case is higher and more favorable for work at the lowest test section densities than in other absorption techniques investigated to the present. The instrument was used in an investigation of air flows about a sphere and a wedge, and in the undisturbed stream. The flow was maintained constant for all portions of the test at Mach 1.95, Re∕in. ∼200, test section static pressure ∼80 μ Hg. Plots of the original and the reduced data show adequate internal consistency and a qualitative conformity with expected configurations.

Effect of Space Charge Fields on Polarization Reversal and the Generation of Barkhausen Pulses in Barium Titanate

A. G. Chynoweth

J. Appl. Phys. 30, 280 (1959); http://dx.doi.org/10.1063/1.1735152 (6 pages) | Cited 19 times

Online Publication Date: 16 June 2004

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The rate of generation of Barkhausen pulses in barium titanate when the polarization direction is slowly reversed is profoundly influenced by the form of the voltage cycling given to the crystal. It is concluded that the rate of nucleation of new domains is determined by the field near the electrodes which, in turn, is the resultant of the applied field and a relaxing space charge field. This result follows directly if the Barkhausen pulses represent individual nucleations though this assumption is not crucial since the generation rate of the pulses parallels the total current at all stages of the polarization reversal. It is concluded also that the majority of the Barkhausen pulses occur independently of each other and of their surroundings.

Recombination Centers on Ion‐Bombarded and Vacuum Heat‐Treated Germanium Surfaces

Shyh Wang and George Wallis

J. Appl. Phys. 30, 285 (1959); http://dx.doi.org/10.1063/1.1735153 (6 pages) | Cited 5 times

Online Publication Date: 16 June 2004

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Germanium surfaces were bombarded with argon ions and then heat‐treated under high vacuum. Room‐temperature values of surface recombination velocity, surface conductivity, dark field effect, and field effect under illumination were measured after successive heat treatments. In addition, the temperature dependence of these quantities was determined. It was confirmed that after annealing of the bombardment damage, a large number of acceptor type surface states approximately clamped the surface potential. Two types of recombination centers were identified: type 1, located near the middle of the gap and type 2, located near the valence band. The various heat treatments produced changes in the density of the type 1 centers but did not appear to effect the density of the type 2 centers.

Space‐Charge Simulation in an Electrolytic Tank

T. Van Duzer and G. R. Brewer

J. Appl. Phys. 30, 291 (1959); http://dx.doi.org/10.1063/1.1735154 (11 pages) | Cited 8 times

Online Publication Date: 16 June 2004

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This paper describes a method for the simulation of space charge in an electrolytic tank by the introduction of currents into the electrolyte by means of sources projecting through the tank floor. The theory and design criteria for this space‐charge simulation system are presented. This method of simulation is used as a means for introducing detailed space‐charge effects into the determination of electron trajectories in axially symmetric, high‐perveance electron guns. The trajectories determined by use of this system are compared with beam characteristics measured experimentally.

Densification during Sintering in the Presence of a Liquid Phase. I. Theory

W. D. Kingery

J. Appl. Phys. 30, 301 (1959); http://dx.doi.org/10.1063/1.1735155 (6 pages) | Cited 309 times

Online Publication Date: 16 June 2004

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The driving force leading to densification during sintering in the presence of a liquid phase and the material transport phenomena have been analyzed and relationships for the densification rate during the rearrangement process, the solution‐precipitation process, and the final coalescence process have been determined. These relationships allow an experimental determination of the mechanism of sintering in the presence of a liquid phase on the basis of the time, particle size and temperature dependence of the densification rate. In addition, they allow direct calculations of densification rates to be made for certain simple systems for which property data are available.

Densification during Sintering in the Presence of a Liquid Phase. II. Experimental

W. D. Kingery and M. D. Narasimhan

J. Appl. Phys. 30, 307 (1959); http://dx.doi.org/10.1063/1.1735156 (4 pages) | Cited 58 times

Online Publication Date: 16 June 2004

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Experimental measurements of the densification rate and microstructure changes taking place during sintering of the iron‐copper system, which is typical of those systems showing spheroidal grain development, indicate that in this system the rate of densification during liquid phase sintering is controlled by diffusion through a liquid film between particles. Dependence of the sintering rate on time, particle size and temperature are in agreement with theoretical predictions. A theoretical estimation of the sintering rate is in good agreement with experimental measurements.

High‐Speed Switching Diodes from Plastically Deformed Germanium

G. L. Pearson and R. P. Riesz

J. Appl. Phys. 30, 311 (1959); http://dx.doi.org/10.1063/1.1735157 (2 pages) | Cited 1 time

Online Publication Date: 16 June 2004

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Diffused diodes, fabricated from plastically deformed germanium, were examined for high‐speed switching response. The degradation of minority carrier lifetime caused by dislocations generated during plastic deformation greatly reduced the minority carrier storage effect and permitted fabrication of diodes with turnoff times of the order of 10−9 sec.

Temperature Coefficients of Resistance of Metallic Films in the Temperature Range 25° to 600°C

Richard B. Belser and Walter H. Hicklin

J. Appl. Phys. 30, 313 (1959); http://dx.doi.org/10.1063/1.1735158 (10 pages) | Cited 29 times

Online Publication Date: 16 June 2004

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The temperature coefficients of resistance (TCR) of films of sputtered Au, Ir, Mo, Ni, Pd, Pt, Rh, Ta, and W, of evaporated Al, Cr, Ti, and Zr, and of the alloy films Pt☒Au, Pt☒Ir, and Pt☒Ni have been measured in vacuo over the temperature range 25° to 600°C; the film thickness range was 75 to 2000 A. The TCR values of films of the substantially pure metals were in the range ⅓ to ⅔ those of the respective bulk metals whether deposited on glass, Vycor, or Stupalith substrates. The departure of the conditions of growth of the film from those usual for the bulk metal, i.e., rapid cooling effects and impurities present, contributed imperfections which reduced the TCR of the film. The TCR values of alloy films were low, 0.0004 per °C for Au☒Pt, and resistivities were 3 to 4 times that of either constituent. The TCR values of sputtered films of Mo, W, and Ta and of evaporated Cr, Zr, and Ti were generally less than 0.0001 per °C. Electron diffraction examination of films of these latter metals revealed oxide inclusions in the films. The presence of the oxide of the metal reduced the TCR and increased the R∕sq of the film as compared to those of the pure metal. Only films of gold, platinum, and iridium were corrosion resistant in air near 600°C. Overcoats of evaporated SiO provided partial protection for the others. Powers up to 15 watts were dissipated by refractory metal films onlymath by ☒ in. and about 750 A thick. These high values contrasted with less than ¼ w for a gold film of similar dimensions.

Density Change in Silicon upon Melting

R. A. Logan and W. L. Bond

J. Appl. Phys. 30, 322 (1959); http://dx.doi.org/10.1063/1.1735159 (1 page) | Cited 6 times

Online Publication Date: 16 June 2004

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The density of both solid and liquid silicon has been measured in the vicinity of its melting point. From the average of several determinations, the increase in density upon melting is 9±1%.

Pulse Width Dependence of the Switching Velocity in BaTiO3 Crystal

K. Husimi and K. Kataoka

J. Appl. Phys. 30, 323 (1959); http://dx.doi.org/10.1063/1.1735160 (2 pages) | Cited 1 time

Online Publication Date: 16 June 2004

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The maximum switching velocity (ΔP∕Δt)max⋅1∕Ps in BaTiO3 single crystals, obtained by the ultrasonic method, is discussed not only as the function of the applied pulse field, but also of the pulse width. Maximum switching current response (dP∕dt) measured by the single pulse method and expressed as the exponential function of the field by Merz, is also considered as the limiting case of our expression as the applied pulse width becomes infinitely wide.

On the Effect of Nonequilibrium Vacancies on the Kinetics of Kirkendall Diffusion

H. Fara and R. W. Balluffi

J. Appl. Phys. 30, 325 (1959); http://dx.doi.org/10.1063/1.1735161 (5 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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Vacancy diffusion models which predict parabolic diffusion‐penetration kinetics implicitly assume that vacancy equilibrium is maintained everywhere. However, a nonequilibrium vacancy distribution is generally established by the pumping action of the chemical gradient in the Kirkendall effect. A more general diffusion model is, therefore, developed in which vacancies are not necessarily maintained in equilibrium. The behavior of the model is then investigated and nonparabolic kinetics are found. However, the kinetics approach those of the equilibrium model as either the vacancy lifetime approaches zero or as the diffusion time becomes very long. The applicability of the equilibrium model, therefore, depends upon the particular system and diffusion time. The results are compared with experiment, and it is concluded that nonparabolic effects are probably of little importance in usual face‐centered‐cubic metallic systems by the time diffusion measurements are made by conventional sectioning methods, i.e., when Dt>∼10−5 cm2.

Model Wave Function Study of Negative Ion Photodetachment in Oxygen

J. J. Brehm

J. Appl. Phys. 30, 329 (1959); http://dx.doi.org/10.1063/1.1735162 (5 pages) | Cited 1 time

Online Publication Date: 16 June 2004

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The total cross section for O− photodetachment is computed using an analytical model to give agreement with the data obtained by Branscomb, Smith, and Burch. For the calculation of the electric dipole matrix element single‐electron wave functions are constructed for the initial and final states which reflect the short range of the interaction between the neutral atom and the extra electron. These are written in terms of two parameters which are determined in order to fit the experimental data. The bound state parameter β gives an indication of the weak binding of the system and also gives a measure of the ``size'' of the ion. The continuum state parameter, the s‐wave phase shift δ, gives the total cross section for the low energy elastic scattering of electrons by O atoms.

Effect of Dislocations on the Thermal Conductivity of Lithium Fluoride

R. L. Sproull, M. Moss, and H. Weinstock

J. Appl. Phys. 30, 334 (1959); http://dx.doi.org/10.1063/1.1735163 (4 pages) | Cited 49 times

Online Publication Date: 16 June 2004

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Measurements of the thermal conductivity K of Harshaw LiF crystals were made over the temperature range 2°–100°K. A freshly cleaved crystal exhibited K values in agreement with the measurements of Berman, Foster, and Ziman (1956). Annealing raised the maximum K by a factor of two. Dislocations were added by compression, and the dislocation density was determined by the methods of Gilman and Johnston. The K values below 30°K for the deformed specimens were approximately proportional to T2, in agreement with Klemens' theory, but the reduction in K by introduction of dislocations was much larger than Klemens' predictions. The phonon mean free path when limited by dislocation scattering was found to be approximately (4×106)∕DT, where D is the number of dislocation lines∕cm2 and T is the absolute temperature.

Pressure Dependence of the Viscoelastic Behavior of Polyisobutylene

Harkrishan Singh and A. W. Nolle

J. Appl. Phys. 30, 337 (1959); http://dx.doi.org/10.1063/1.1735164 (5 pages) | Cited 20 times

Online Publication Date: 16 June 2004

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The absorption of 4 mc∕sec ultrasonic waves in polyisobutylene is measured as a function of temperature, for various pressures. The extreme limits of these variables are 1 to 1400 atmos and −20°C to 80°C, respectively. Approximate measurements of propagation velocity are also obtained. Pulse reflection apparatus is used. A magnetically actuated holder places the sample in the signal path or removes it. Pressure‐volume data are obtained for polyisobutylene at 30°C by means of a capillary dilatometer fitted with electrical contacts, in which the sample is placed with mercury. The expected behavior of viscoelastic relaxation times with temperature and pressure is computed by adapting a theory due to Bueche. With additional assumptions concerning the compressibility, the theory gives a shift of the constant‐frequency absorption maximum of 0.025 C°∕atmos, in approximate agreement with experiment.

Electrodynamic Containment of Charged Particles

R. F. Wuerker, H. Shelton, and R. V. Langmuir

J. Appl. Phys. 30, 342 (1959); http://dx.doi.org/10.1063/1.1735165 (8 pages) | Cited 299 times

Online Publication Date: 16 June 2004

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Electrically charged iron and aluminum particles having diameters of a few microns have been contained in a confined region of space by means of alternating and static electric fields. The theory is essentially that of alternating gradient focusing; here the motion is governed by Mathieu's equation. Under certain circumstances when many particles are confined the three dimensional focusing force and the Coulomb repulsion results in a ``crystaline'' array which can be ``melted'' and reformed.

Thermal Expansion of Ice

T. R. Butkovich

J. Appl. Phys. 30, 350 (1959); http://dx.doi.org/10.1063/1.1735166 (4 pages)

Online Publication Date: 16 June 2004

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Linear thermal expansion coefficients of natural and artificial single ice crystals, commercial ice, and snow ice were determined in the temperature range near 0 to −30°C. There was no measurable difference in the coefficients of linear thermal expansion parallel and normal to the c axis of single crystals or polycrystalline ice. However a steady decrease of expansion coefficients with each succeeding measurement on the same ice specimen was observed. The total decrease was of the order of 2×10−6, while an estimated error calculation yielded a value of about 4×10−7. An entirely satisfactory explanation of this phenomenon cannot be given at this time, and further investigation on this point would be desirable. Values of Cv, the specific heat at constant volume, were calculated from thermodynamic relationships. Average Cp∕Cv values were 1.030. Gruneisen's constant was found to average 0.78, and essentially independent of temperature between 0°C and −30°C.

Impurity Compensation and Magnetoresistance in p‐Type Silicon

Donald Long, C. D. Motchenbacher, and John Myers

J. Appl. Phys. 30, 353 (1959); http://dx.doi.org/10.1063/1.1735167 (10 pages) | Cited 2 times

Online Publication Date: 16 June 2004

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A new method is proposed for determining the separate concentrations of acceptor and donor impurities in crystals of p‐type silicon, and thereby the degree of compensation of acceptors by donors. The method involves finding the total concentration of impurities in a sample from a measurement of the weak‐field transverse magnetoresistance at 77°K and combining this result with the excess of acceptors over donors determined from a room‐temperature resistivity or Hall effect measurement. An empirical ``master curve'' of magnetoresistance vs impurity density has been constructed for this purpose. The impurity densities for the master curve were measured by the usual method of fitting a theoretical carrier concentration vs temperature equation to an experimental curve obtained from Hall effect data.

Line Widths in Polycrystalline Yttrium Iron Garnet

L. G. Van Uitert, F. W. Swanekamp, and S. E. Haszko

J. Appl. Phys. 30, 363 (1959); http://dx.doi.org/10.1063/1.1735168 (3 pages) | Cited 5 times

Online Publication Date: 16 June 2004

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The line widths at the half‐power point for ferromagnetic resonance in a number of polycrystalline yttrium iron garnet samples have been measured at 16 kmc.
It has been determined that, starting with mixtures of Y2O3 and Fe2O3, sound parts with small grain size and having line widths as low as 35 to 40 oersteds can be obtained on the iron‐rich side of stoichiometry in Y3Fe5O12. However, narrower line widths (∼20 oersteds) in large grained materials are obtained by using less than the stoichiometric amount of iron and firing at temperatures higher than 1450°C. This is due to minimizing the disrupting influences of oxygen loss in iron‐rich areas at high temperatures.
Line widths do not appear to be broadened by the addition of small amounts of nickel, cobalt, or manganese to convert excess iron to high resistance forms of spinel in the iron‐rich compositions.

Magnetic Moments of Alloys and Compounds of Iron and Cobalt with Rare Earth Metal Additions

E. A. Nesbitt, J. H. Wernick, and E. Corenzwit

J. Appl. Phys. 30, 365 (1959); http://dx.doi.org/10.1063/1.1735169 (3 pages) | Cited 25 times

Online Publication Date: 16 June 2004

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In order to determine whether ferromagnetic or antiferromagnetic exchange coupling would result from alloying the rare earth metals with cobalt or iron, a number of melts were made containing these elements. The data on saturation magnetization with composition and on saturation magnetization with temperature obtained on the cobalt‐gadolinium system indicates strongly that antiferromagnetic exchange coupling exists in this system.

Azimuthal Electron Flow in a Spherical Diode

William E. Waters

J. Appl. Phys. 30, 368 (1959); http://dx.doi.org/10.1063/1.1735170 (6 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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Solutions of Poisson's equation for a space‐charge‐limited spherical diode, in which electron trajectories are great circles rather than radial lines, are developed. It is shown how Poisson's equation may be separated to yield ordinary differential equations. The radial equation is solved analytically, whereas accurate numerical solutions of the azimuthal equation are given. A method of truncating the flow so as to produce a ``bowl‐shaped'' electron gun, leading eventually to an annular electron beam, is presented, along with power‐series solutions of Laplace's equation both inside and outside the region of the flow. The latter series are useful for calculating the shapes of anodes and focusing electrodes.

Sputtering Yield of Germanium in Rare Gases

N. Laegreid, G. Wehner, and B. Meckel

J. Appl. Phys. 30, 374 (1959); http://dx.doi.org/10.1063/1.1735171 (4 pages) | Cited 11 times

Online Publication Date: 16 June 2004

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Sputtering yields of germanium bombarded by Xe+, Kr+, A+, Ne+, and He+‐ions under normal incidence at energies up to 400 ev have been determined. Yield vs ion energy curves consist of three parts; (1) a low‐energy tail (possibly caused by a process of stepwise sputtering), (2) a region in which yield rises proportionally with ion energy, and above ion velocities of ∼3×106 cm∕sec, (3) a region in which the yield rises less than proportionally with ion energy.
The slope in the proportional region is largely determined by the energy transfer factor, η=4m1m2∕ (m1+m2)2. Surprisingly, the ``cut in'' energies do not follow V0∼H∕η (H=heat of sublimation) but are found to be much lower than expected for the lighter gases. The empirical result, V0∼H(m1)☒∕η (m1=atomic weight of ion), is not yet understood.

Experimental Method for Developing Minute Flaw Patterns in Glass

W. C. Levengood

J. Appl. Phys. 30, 378 (1959); http://dx.doi.org/10.1063/1.1735172 (9 pages) | Cited 12 times

Online Publication Date: 16 June 2004

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A new chemical etching technique was used to study minute flaw patterns in glass. The etched structure disclosed that the minute defects react to the chemical treatment in a different manner than ordinary fissures. Flaw patterns formed at the tips of slow‐moving internal cracks were analogous to dislocation phenomena in crystals.
Oriented and repeating flaw groupings were observed in various types of glass. These patterns are produced above the ``strain point'' and were shown to be influenced by permanently induced stresses and internal homogeneity.
Fracturing by localized stresses created flaw patterns radiating from the point of origin with shapes similar in appearance to shock wave phenomena. The impact breaking strength of glass containers was directly influenced by the number of flaws. The flaw distribution decreased rapidly with decreasing diameter of glass fibers.

Domain Boundary Configurations during Magnetization Reversals

J. J. Becker

J. Appl. Phys. 30, 387 (1959); http://dx.doi.org/10.1063/1.1735173 (4 pages) | Cited 12 times

Online Publication Date: 16 June 2004

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The signal resulting from the application of an alternating field while a magnetization reversal is taking place yields information about the total domain boundary area contributing to the reversal at each moment. This technique is used to show that the variation in rate during a reversal in a 65 Permalloy tape core corresponds to changes in the area of moving domain boundary, whereas in a 3¼% silicon‐iron single crystal picture frame specimen the area of moving domain boundary remains approximately constant, and variations in reversal rate therefore correspond to variations in velocity.

Magnetocrystalline Anisotropy Constant of 3.1% Si☒Fe at Room Temperature and Below

C. D. Graham

J. Appl. Phys. 30, 391 (1959); http://dx.doi.org/10.1063/1.1735174 (2 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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The first crystal anisotropy constant of a 3.1% Si☒Fe alloy has been determined from torque measurements on a {100} single‐crystal disk, in fields up to 20 000 oersteds and at temperatures of 77, 195, and 300°K. The values of K1 at these three temperatures are 425±10×103, 405±10×103, and 365±10×103 ergs∕cm3.

Effect of Oxide Impurities on the Thermoelectric Powers and Electrical Resistivities of Bismuth, Antimony, Tellurium, and Bismuth‐Tellurium Alloys

R. A. Horne

J. Appl. Phys. 30, 393 (1959); http://dx.doi.org/10.1063/1.1735175 (5 pages) | Cited 8 times

Online Publication Date: 16 June 2004

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The thermoelectric powers of bismuth and antimony are only slightly altered by the presence of Bi2O3 and Sb2O3, respectively, and the electrical resistivities are increased. The thermoelectric power of tellurium, however, is extremely sensitive to TeO2 imputities. Bismuth‐tellurium alloys show greatest sensitivity to oxide impurities when their composition is in the range corresponding to Bi2Te3. The thermoelectric powers of these materials depend in detail on the manner in which the thermal gradient is applied during measurement.
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