摘要:

In recent years sodalite, Na8Al6Si6O24X2, whereXis Cl, Br, or I, has received wide attention as a cathodochromic material. The utility of sodalite, however, is severely restricted because of damage produced after repeat write‐erase cycles. This damage was investigated and found to be of two kinds. The first kind was considerable loss of potential color centers, i.e., after a certain number of write‐erase cycles the material would not color up to the original optical density. The second kind was build up of permanent coloration which could not be removed on exposure to bleaching light but could be removed by heat. Electron microprobe, electron spectroscopy for chemical analysis, thermogravimetric analysis, x rays, and a variety of other analytical tools were used to understand the causes of damage. Considerable loss of sodium and a smaller loss of halogen ions on continued electron‐beam irradiation was found to be closely associated with the damage. Possibility of heat generated by the electron beam was discounted as the source of damage.

ISSN:0021-8979    

DOI:10.1063/1.1663845

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Adopting the Cohen nonellipsoidal nonparabolic (NENP) model as the energy band of bismuth, calculations of the conductivity tensor in the presence of ultrasound propagating parallel to a dc magnetic field are performed by using a quantum‐mechanical treatment which is valid at high frequencies and in strong magnetic fields. It is found that the longitudinal resistivity oscillates with the dc magnetic field. However, these ``giant quantum oscillations'' will be diminished by increasing the sound frequency. This dependence of the longitudinal resistivity on the dc magnetic field arises from the nonlinear effect of the energy bands owing to the NENP band structure of bismuth.

ISSN:0021-8979    

DOI:10.1063/1.1663846

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper presents the results of calculations for the amplification coefficient and the velocity of Bleustein‐Gulyaev waves in tetragonal and hexagonal crystals (classes 4 and 6) which are coupled with a semiconductor through an infinitesimally small vacuum gap. The conditions for existence of these waves are discussed. Detailed calculations of the amplification coefficient and velocity are performed for the system which consists of silicon and lithium iodate.

ISSN:0021-8979    

DOI:10.1063/1.1663847

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Zn and Sn have been deformed plastically by an ultrasonic system operating at 22.5 kHz. The amplitude dependence of the internal friction was correlated with the presence or absence of twins. Friedel's relation between the dimensions of a twin formed in a burst from a single source was found to hold for Zn but not for Sn. Assuming that each twin forms during a single stress pulse, the rate of operation of a Frank‐Read source is found to be physically reasonable for Zn, with a dislocation velocity approaching the speed of sound, but too high for Sn. We conclude that the assumption that twins form in a single burst is justified for Zn, giving a linear growth rate≳3×102m/sec, but not for Sn, implying a slower growth rate.

ISSN:0021-8979    

DOI:10.1063/1.1663848

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The initial stages in the oxidation of Nb have been studied by the uv‐photoemission technique for photon energies below 12 eV. Changes of structure in the electron distribution curves for different oxygen exposures and temperatures are correlated with formation of different types of Nb oxides. Electronic structure changes due to formation of at least three different oxides or mixtures of oxide have been observed. NbO2and the NbO oxides seem to form first as a thin protective layer. The pentoxide, Nb2O5, is obtained after heavy oxidation. Practical implications of the formation of NbO in the interface between Nb2O5and Nb metal are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1663849

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Atomic ordering in the V&sngbnd;Ni and V&sngbnd;Co A 15‐type phases has been studied using neutron diffraction. The V&sngbnd;Ni structure is shown to be ordered to the maximum extent permitted by the ``off stoichiometric'' composition, V77.5Ni22.5. The V&sngbnd;Co structure possessing the ``ideal'' composition V75.0Co25.0is also highly ordered. However, the V&sngbnd;Co diffraction data are less accurate due to neutron absorption by the cobalt atoms and interference from the sample holder. No magnetic structures were detected in the V&sngbnd;Co phase at 4.2 °K.

ISSN:0021-8979    

DOI:10.1063/1.1663850

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The kinetics of relaxation of surface‐compressive stresses in tempered polycrystalline aluminum oxide were studied. Stress relaxation was observed at temperatures of 775°C and higher. Analysis of the data suggests that the relaxation occurred by Coble creep, which represents the first evidence, although indirect, of the existence of the Coble creep mechanism in ceramics.

ISSN:0021-8979    

DOI:10.1063/1.1663851

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The stacking‐fault tetrahedron in an epitaxial Si layer was observed in the electron‐beam‐induced current mode using the scanning electron microscope. The contrast mechanism involved in the stair‐rod partial dislocations of the stacking‐fault tetrahedron was analyzed on the basis of a simplified model. The calculation seems to fit the experiment since good agreement was obtained between the observed and calculated results.

ISSN:0021-8979    

DOI:10.1063/1.1663852

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A series of capacitance and dissipation factor (tan&dgr;) measurements were made on single‐crystal specimens of synthetic proustite (Ag3AsS3). The results showed a rise in the dielectric constant (∼3000) with increasing temperature as well as with decreasing frequency (dispersion effects). A model based on an equivalent‐circuit analog of a two‐layer dielectric was used to fit theoretical curves to the data. In this model, one layer is considered to be the space‐charge region, while the other is the crystal bulk. The theoretical and experimental curves show the same general features, although some quantitative differences exist. The true dielectric constant is concluded to be &egr;′∥c= 22.

ISSN:0021-8979    

DOI:10.1063/1.1663853

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Finely grained films of three cermets‐MgO/Au, MgO/Ag, and MgO/Ni‐have been grown by rf sputtering from composite targets. Electron‐microscopic studies show that MgO/Au and MgO/Ag films consist of small crystallites (usually <150 Å) of both MgO and Au or Ag. In MgO/Ni films, it appears that amorphous Ni particles are embedded in a polycrystalline MgO matrix. These cermet films are good secondary‐electron emitters, especially in cases where differential‐sputtering effects are large. In MgO/Au films, the Au particles sputter much faster than MgO resulting in a MgO‐rich surface layer. In MgO/Ag films, the differential‐sputtering effect is smaller, probably due to stronger interaction between MgO and Ag crystallites. In MgO/Ni, the Ni particles sputter slower than MgO resulting in a slightly Ni‐rich surface (and hence in poorer electron‐emission properties). The small particle sizes and the presence of metallic particles in the bulk of the films greatly reduce surface charging.

ISSN:0021-8979    

DOI:10.1063/1.1663854

出版商:AIP    

年代:1974

数据来源: AIP