摘要:

The thermal resistivity, Seebeck coefficient, electrical resistivity, and Hall mobility of Ge‐Si alloys have been measured throughout the Ge‐Si alloy system as functions of impurity concentration in the range 2×1018−4×1020cm−3, and of temperature in the range 300°–1300°K. A qualitative interpretation of these properties is given. For power conversion, boron and phosphorus were found to be usefulp‐type andn‐type impurities, respectively, because of their high solid solubilities. At 1200°K, the maximum values of the dimensionless figure of meritzTwere 0.8 forp‐type Ge0.15‐Si0.85alloy doped to 2.1×1020cm−3holes, and 1.0 forn‐type Ge0.15‐Si0.85alloy doped to 2.7×1020cm−3electrons. The maximum over‐all efficiency of a stable generator operating between 300°–1200°K, using the bestp‐type andn‐type materials was computed to be 10%.

ISSN:0021-8979    

DOI:10.1063/1.1713126

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A method is described for determining a variable gamma‐ray absorption coefficient in a sample from measurements made outside the sample, and the applicability of the method to other radiological problems (e.g., positron scanning) is pointed out. An experimental test of the method is described, and it is concluded that the method works well.

ISSN:0021-8979    

DOI:10.1063/1.1713127

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The anelastic behavior of natural quartz has been modified by doping with alkali ions. Three blocks cut from a single crystal of Brazilian quartz were doped with lithium, sodium, and potassium, respectively, by electrodiffusion at 500°C using a vapor‐plated anode of a halide containing the desired alkali ion. Fundamental 1‐Mc/sec, AT‐cut shear mode resonators were fabricated from each block. Measurements ofQ−1and resonant frequency were made from liquid‐helium temperatures to near the quartz inversion point at 573°C. For a resonant frequency of 5 Mc/sec internal friction peaks were evident in the low‐temperature region with sodium doping giving peaks at 50° and 140°K, lithium a peak near 100°K, and potassium a peak near 200°K. The activation energies ranged from 0.06 to 0.2 eV and the relaxation times were all the order of 10−12sec. The low‐temperature behavior induced by sodium doping is of special interest since it is identical to that of certain synthetic quartz crystals. All three doped samples exhibited an exponentially increasing loss above room temperature. In each case the activation energy of the exponential loss corresponded to the activation energy for diffusion of the particular alkali ion, approximately 1 eV. Although one would infer that the loss is due only to alkali ion diffusion, it is felt that a more complex mechanism is involved at high temperatures.

ISSN:0021-8979    

DOI:10.1063/1.1713128

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Stoichiometric TiNi and its alloys containing Cu or excess Ni were measured to study the lattice component of the thermal conductivity. The low‐temperature phonon mean‐free‐path is constant, depends upon solute species, and increases with solute concentration. In addition, the ideal component of the electrical resistivity shows theT2dependence below 100°K found for the element and alloys with this same electron number. Values of the Fermi energy, effective mass, and the relative valence of the solutes are derived. Finally, one of the alloyed samples exhibits phase changes which are believed related to those seen in the pure material at temperatures above 300°K.

ISSN:0021-8979    

DOI:10.1063/1.1713129

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The minimum pressure vs molecular size at which the vapor lubrication of graphite is effective (Savage's ``operating curve'') can be transformed to a linear law. The law must demand the nucleation of a liquid‐like adsorbed film, and this is reconciled with recent studies of physical adsorption on graphite. A physical model, consistent with the law, is adumbrated.

ISSN:0021-8979    

DOI:10.1063/1.1713130

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Multicomponent alloy films of sheet resistivity between 100 and 600 &OHgr;/sq. have been fabricated on substrates at 300°C, and several substrate temperatures have been investigated for film resistivities of 250 &OHgr;/sq. These films have been subjected to several thousand hours storage in air at elevated temperatures. When aged at 300°C, films of high resistivity increase in resistance until open, while films of low resistivity reach a resistance maximum, then decrease through a minimum, and finally increase in resistance until opening. The use of a protective overcoating of SiO enhances the film stability during extended storage. The normalized resistance of protected films always decreases, with the lower substrate temperature films exhibiting larger decreases. This normalized resistance decrease is accompanied by a linearly related increase in the temperature coefficient of resistance. The electrical properties of these films may be explained if we postulate that the conductivity is the result of several mechanisms, some resulting from normal metallic conduction through a defect film, whereas others result from activated charge transfer between adjacent grains. The electrical behavior of the protected films under thermal aging is the result of defect anneal and grain growth. For the unprotected films we must also introduce the concept of selective oxidation.

ISSN:0021-8979    

DOI:10.1063/1.1713131

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

This is a preliminary report on square hysteresis loops obtained on polycrystalline yttrium iron garnets that have Tb3+or Eu3+partially replacing the Y3+ions. Reasonably square hysteresis loops that are technologically important can be produced. In addition, a cobalt‐containing‐garnet responds to a magnetic annealing treatment and has substantial values of uniaxial anisotropy at room temperature. This work indicates a method of producing other garnets which will respond to the magnetic annealing process.

ISSN:0021-8979    

DOI:10.1063/1.1713132

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Experimental evidence is presented which verifies Middlehoek's recent extension of the Ne´el theory relating the coercivity with film thickness variations. Under special preparatory conditions ``inverted'' NiFe films on glass substrates were produced with excellent reproducibility. Partial oxidation leading to antiferromagnetic inclusions was shown to be absent. Resolution of the substrate temperature control problems using metal substrates in the plasma environment enabled us to show that a uniaxial anisotropy can only be induced into sputtered NiFe films over a limited temperature region. Temperature control during film growth also made possible a direct correlation of film morphology with the magnitude and uniformity of the dispersion of the easy axis of magnetization and the resultant critical field for wall motionHc. Typical coercivityHc, anisotropy field strengthHK, and dispersion measurements on 700‐Å NiFe films on very smooth 25 cm2Ag: Cu&sngbnd;SiO substrates were:Hc=1.92±0.07 Oe,HK=2.85±0.03 Oe, dispersion=1.0±0.0°. Special problems pertaining to film growth in a plasma environment are discussed. A typical Lorentz micrograph of a sputtered NiFe film deposited directly onto a microscope grid is given.

ISSN:0021-8979    

DOI:10.1063/1.1713133

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The room‐temperature current‐voltage characteristics for thermally grown Al2O3dielectric films sandwiched between the Al base electrode and the Zn, Sn, or Au counter electrode were studied. Experimentally, voltage ranges were found for which the Schottky mechanism appears to be dependent on the energy band structure of the metal‐insulator‐metal configuration. The film current changes from a logJ‐V½(the Schottky mechanism) dependency to a logJ‐Vdependency at a particular applied voltageVB. Empirically, the sum &phgr;+eVB=&psgr;, where &phgr; is the metal‐insulator barrier, is in agreement with the work function &psgr; of the positive metal electrode. In consideration of thisad hocagreement, the contact potential &psgr;CP=&Dgr;&phgr;+&Dgr;eVB, where &Dgr;&phgr; is the difference (asymmetry) in the calculated metal‐insulator barrier for positive and negative polarities, and &Dgr;eVBis the difference in the voltages for the change of mechanisms for the corresponding polarities. The mechanism by which the film currents change from the Schottky emission to the logJ‐Vdependency at a particular voltageVBis not understood.

ISSN:0021-8979    

DOI:10.1063/1.1713134

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

We propose to demonstrate that a coherent description of pyrolytic graphite (PG) layer‐plane phenomena can be based on a parabolic two‐band system with cylindrical equal‐energy surfaces. In this simple two‐band model (STB model), band overlap and effective mass must be interpreted as phenomenological parameters to be derived from experiments on highly heat‐treated pure PG. Withp‐type (boron‐doped) specimens, the objective is to describe the situation from the shift of the Fermi level, on the assumption that the presence of trapping centers would not inject major perturbations in the band structure. (1)Galvanomagnetic effects: As derived from zero‐field resistivity and magnetoresistance mobility, the intrinsic carrier concentration and its variation with temperature in the range 0° to 1500°K implies that past a given graphitization stage band‐structural features may no longer be seriously affected by the size of the carbon networks. Above room temperature the carrier concentration increases almost linearly and in accordance with a constant mean effective mass of about 0.0125m0; low‐temperature data suggest an energy‐band overlap of 0.01 eV, which may be temperature‐sensitive through thermal expansion. (2)Thermoelectric effects: Along the layer planes the carrier‐mobility behavior is strong evidence for a relaxation time that may be taken of the formE−½. On this basis it can be shown that the STB model accounts for the Seebeck coefficient, provided that exact Fermi‐Dirac statistics are used in conjunction with standard equations for semimetallic systems. (3)Magnetothermal effects: The discovery of a substantial electronic component in the low‐temperature thermal conductivity of PG layer planes makes it desirable to develop methods of separating lattice‐phonon and charge‐carrier contributions to heat transport in graphite. It is shown that saturation magnetothermal conductivity measurements can be successfully utilized for this purpose.

ISSN:0021-8979    

DOI:10.1063/1.1713135

出版商:AIP    

年代:1964

数据来源: AIP